Merge branch 'master' of https://github.com/rm-dr/lamb

.gitignore

@@ -1,7 +1,13 @@
+# Python dev files
 venv
 __pycache__
 
+# Python build files
 *.egg-info
 *.spec
 build
-dist
+dist
+
+# Misc
+*.gif
+misc/secrets.sh

.vscode/settings.json

@@ -1,11 +1,14 @@
 {
     "cSpell.words": [
+        "appendleft",
         "autochurch",
+        "delmac",
         "Endnodes",
         "freevar",
         "mdel",
         "onefile",
         "Packrat",
+        "printables",
         "pyparsing",
         "rlimit",
         "runstatus",

README.md

@@ -1,25 +1,43 @@
-# Lamb: A Lambda Calculus Engine
+# 🐑 Lamb: A Lambda Calculus Engine
 
-![Lamb screenshot](./misc/screenshot.png)
+![Lamb Demo](https://github.com/rm-dr/lamb/assets/96270320/d518e344-e7c8-47ed-89c4-7ce273bf4e2d)
 
-## Installation
 
-### Method 1: PyPi (not yet)
+
-1. Put this on PyPi
+## :brain: What is lambda calculus?
-2. Write these instructions
+
+ - [video 1](https://www.youtube.com/watch?v=3VQ382QG-y4): Introduction and boolean logic. The first few minutes are a bit confusing, but it starts to make sense at about [`6:50`](https://youtu.be/3VQ382QG-y4?t=400)
+
+ - [video 2](https://www.youtube.com/watch?v=pAnLQ9jwN-E): Continuation of video 1. Features combinators and numerals.
+
+ - [blog](https://www.driverlesscrocodile.com/technology/lambda-calculus-for-people-a-step-behind-me-1): Another introduction. Moves slower than the two videos above and doesn't assume CS knowledge. Four-part series.
+
+ - [handout](https://static.betalupi.com/ormc/Advanced/Lambda%20Calculus.pdf): A handout I've written on lambda calculus.
+
+## :package: Installation
+
+### Method 1: [PyPi](https://pypi.org/project/lamb-engine)
+1. *(Optional but recommended)* make and enter a [venv](https://docs.python.org/3/library/venv.html)
+	- **On Windows, run the following in cmd or powershell:**
+	- `cd Desktop`
+	- `python -m venv lamb`
+	- `.\Scripts\activate`
+2. `pip install lamb-engine`
+3. `lamb`
 
 ### Method 2: Git
 1. Clone this repository.
 2. Make and enter a [virtual environment](https://docs.python.org/3/library/venv.html).
 3. ``cd`` into this directory
 4. Run ``pip install .``
-5. Run ``python .``
+5. Run ``lamb``
 
 -------------------------------------------------
 
-## Usage
+## 📖 Usage
 
-Type lambda expressions into the prompt, and Lamb will evaluate them. \
+
+Type expressions into the prompt, and Lamb will evaluate them. \
 Use your `\` (backslash) key to type a `λ`. \
 To define macros, use `=`. For example,
 ```
@@ -30,70 +48,72 @@ To define macros, use `=`. For example,
 
 Note that there are spaces in `λa.a F T`. With no spaces, `aFT` will be parsed as one variable. \
 Lambda functions can only take single-letter, lowercase arguments. `λA.A` is not valid syntax. \
-Unbound variables (upper and lower case) that aren't macros will become free variables. Free variables will be shown with a `'`, like `a'`.
+Free variables will be shown with a `'`, like `a'`.
 
-Be careful, macros are case-sensitive. If you define a macro `MAC` and accidentally write `mac` in the prompt, `mac` will become a free variable.
+Macros are case-sensitive. If you define a macro `MAC` and accidentally write `mac` in the prompt, `mac` will become a free variable.
 
 Numbers will automatically be converted to Church numerals. For example, the following line will reduce to `T`.
 ```
 ==> 3 NOT F
 ```
 
-If an expression takes too long to evaluate, you may interrupt reduction with `Ctrl-C`.
+If an expression takes too long to evaluate, you may interrupt reduction with `Ctrl-C`. \
+Exit the prompt with `Ctrl-C` or `Ctrl-D`.
+
+There are many useful macros in [macros.lamb](./macros.lamb). Download the file, then load them with the `:load` command:
+```
+==> :load macros.lamb
+```
+
+You can also pass files to lamb directly to have them loaded at startup:
+```
+lamb file1 file2
+```
+
+Use your up/down arrows to recall history.
+
+Have fun!
 
 -------------------------------------------------
 
-## Commands
+## :card_file_box: Commands
 
-Lamb comes with a few commands. Prefix them with a `:`
+Lamb understands many commands. Prefix them with a `:` in the prompt.
 
-`:help` Prints a help message
+`:help` Print a help message
 
 `:clear` Clear the screen
 
 `:rlimit [int | None]` Set maximum reduction limit. `:rlimit none` sets no limit.
 
-`:macros` List macros in the current environment.
+`:macros` List macros.
 
 `:mdel [macro]` Delete a macro
 
-`:save [filename]`\
+`:delmac` Delete all macros
-`:load [filename]` Save or load the current environment to a file. The lines in a file look exactly the same as regular entries in the prompt, but must only contain macro definitions.
+
+`:step [yes | no]` Enable or disable step-by-step reduction. Toggle if no argument is given. When reducing by steps, the prompt tells you what kind of reduction was done last:
+
+ - `M`: Macro expansion
+ - `C`: Church expansion
+ - `H`: History expansion
+ - `F`: Function application
+
+`:expand [yes | no]` Enable or disable full expansion. Toggle if no argument is given. If full expansion is enabled, ALL macros will be expanded when printing output.
+
+`:save [filename]` \
+`:load [filename]` \
+Save or load macros from a file.
+The lines in a file look exactly the same as regular entries in the prompt, but can only contain macro definitions. See [macros.lamb](./macros.lamb) for an example.
 
 -------------------------------------------------
 
-## Internals
-
-Lamb treats each λ expression as a binary tree. Variable binding and reduction are all simple operations on that tree. All this magic happens in [`nodes.py`](./lamb/nodes.py).
-
-**Highlights:**
- - `TreeWalker` is the iterator we (usually) use to traverse our tree. It walks the "perimeter" of the tree, visiting some nodes multiple times.
- - `Node` is the base class for all nodes. Any node has `.left` and `.right` elements, which may be `None` (empty). `Node`s also reference their parent and their direction relative to their parent, to make tree traversal easy.
- - Before any reduction is done, variables are bound via `bind_variables`. This prevents accidental conflicts common in many lambda parsers.
-
--------------------------------------------------
-
-
-## Todo (pre-release, in this order):
- - Fix :save
- - Cleanup warnings
- - Truncate long expressions in warnings
- - Prevent macro-chaining recursion
- - Full-reduce option (expand all macros)
- - step-by-step reduction
- - Cleanup files
- - Update screenshot
- - Update documentation & "internals" section.
- - PyPi package
-
-
 ## Todo:
- - History queue + command indexing
+ - Prevent macro-chaining recursion
- - Show history command
+ - Cleanup warnings
- - Better class mutation: when is a node no longer valid?
+ - Truncate long expressions in warnings
  - Loop detection
- - $\alpha$-equivalence check
+ - Unchurch command: make church numerals human-readable
- - Command-line options (load a file, run a set of commands)
+ - Better syntax highlighting
- - Unchurch macro: make church numerals human-readable
+ - Tab-complete file names and commands
- - Syntax highlighting: parenthesis, bound variables, macros, etc
+ - Load default macros without manually downloading `macros.lamb` (via `requests`, maybe?)
- - Tests

build_bin.py

@@ -1,10 +0,0 @@
-import PyInstaller.__main__
-
-# Run this file to build a standalone executable.
-# pyinstaller does not build cross-platform.
-
-PyInstaller.__main__.run([
-	"lamb/__main__.py",
-	"--onefile",
-	"--console"
-])

lamb/__init__.py

@@ -1,7 +0,0 @@
-from . import utils
-from . import node
-from . import parser
-from . import commands
-
-from .runner import Runner
-from .runner import StopReason

lamb/__main__.py

@@ -1,98 +0,0 @@
-from prompt_toolkit import PromptSession
-from prompt_toolkit.completion import WordCompleter
-from prompt_toolkit import print_formatted_text as printf
-from prompt_toolkit.formatted_text import FormattedText
-from prompt_toolkit.formatted_text import to_plain_text
-from prompt_toolkit.key_binding import KeyBindings
-from prompt_toolkit.lexers import Lexer
-from pyparsing import exceptions as ppx
-
-import lamb
-
-
-# Simple lexer for highlighting.
-# Improve this later.
-class LambdaLexer(Lexer):
-	def lex_document(self, document):
-		def inner(line_no):
-			return [("class:text", str(document.lines[line_no]))]
-		return inner
-
-
-lamb.utils.show_greeting()
-
-
-# Replace "\" with pretty "λ"s
-bindings = KeyBindings()
-@bindings.add("\\")
-def _(event):
-	event.current_buffer.insert_text("λ")
-
-
-r = lamb.Runner(
-	prompt_session = PromptSession(
-		style = lamb.utils.style,
-		lexer = LambdaLexer(),
-		key_bindings = bindings
-	),
-	prompt_message = FormattedText([
-		("class:prompt", "==> ")
-	])
-)
-
-
-r.run_lines([
-	"T = λab.a",
-	"F = λab.b",
-	"NOT = λa.(a F T)",
-	"AND = λab.(a b F)",
-	"OR = λab.(a T b)",
-	"XOR = λab.(a (NOT b) b)",
-	"M = λx.(x x)",
-	"W = M M",
-	"Y = λf.( (λx.(f (x x))) (λx.(f (x x))) )",
-	"PAIR = λabi.( i a b )",
-	"S = λnfa.(f (n f a))",
-	"Z = λn.n (λa.F) T",
-	"MULT = λnmf.n (m f)",
-	"H = λp.((PAIR (p F)) (S (p F)))",
-	"D = λn.n H (PAIR 0 0) T",
-	"FAC = λyn.(Z n)(1)(MULT n (y (D n)))"
-])
-
-
-while True:
-	try:
-		i = r.prompt()
-
-	# Catch Ctrl-C and Ctrl-D
-	except KeyboardInterrupt:
-		printf("\n\nGoodbye.\n")
-		break
-	except EOFError:
-		printf("\n\nGoodbye.\n")
-		break
-
-	# Skip empty lines
-	if i.strip() == "":
-		continue
-
-	# Try to run an input line.
-	# Catch parse errors and point them out.
-	try:
-		x = r.run(i)
-	except ppx.ParseException as e:
-		l = len(to_plain_text(r.prompt_session.message))
-		printf(FormattedText([
-			("class:err", " "*(e.loc + l) + "^\n"),
-			("class:err", f"Syntax error at char {e.loc}."),
-			("class:text", "\n")
-		]), style = lamb.utils.style)
-		continue
-	except lamb.node.ReductionError as e:
-		printf(FormattedText([
-			("class:err", f"{e.msg}\n")
-		]), style = lamb.utils.style)
-		continue
-
-	printf("")

lamb/runner.py

@@ -1,277 +0,0 @@
-from prompt_toolkit import PromptSession
-from prompt_toolkit.formatted_text import FormattedText
-from prompt_toolkit import print_formatted_text as printf
-import enum
-import math
-import time
-
-import lamb
-
-
-class StopReason(enum.Enum):
-	BETA_NORMAL		= ("class:text", "β-normal form")
-	LOOP_DETECTED	= ("class:warn", "Loop detected")
-	MAX_EXCEEDED	= ("class:err", "Too many reductions")
-	INTERRUPT		= ("class:warn", "User interrupt")
-	SHOW_MACRO		= ("class:text", "Displaying macro content")
-
-class MacroDef:
-	@staticmethod
-	def from_parse(result):
-		return MacroDef(
-			result[0].name,
-			result[1]
-		)
-
-	def __init__(self, label: str, expr: lamb.node.Node):
-		self.label = label
-		self.expr = expr
-
-	def __repr__(self):
-		return f"<{self.label} := {self.expr!r}>"
-
-	def __str__(self):
-		return f"{self.label} := {self.expr}"
-
-	def set_runner(self, runner):
-		return self.expr.set_runner(runner)
-
-class Command:
-	@staticmethod
-	def from_parse(result):
-		return Command(
-			result[0],
-			result[1:]
-		)
-
-	def __init__(self, name, args):
-		self.name = name
-		self.args = args
-
-
-class Runner:
-	def __init__(
-		self,
-		prompt_session: PromptSession,
-		prompt_message
-	):
-		self.macro_table = {}
-		self.prompt_session = prompt_session
-		self.prompt_message = prompt_message
-		self.parser = lamb.parser.LambdaParser(
-			action_func = lamb.node.Func.from_parse,
-			action_bound = lamb.node.Macro.from_parse,
-			action_macro = lamb.node.Macro.from_parse,
-			action_call = lamb.node.Call.from_parse,
-			action_church = lamb.node.Church.from_parse,
-			action_macro_def = MacroDef.from_parse,
-			action_command = Command.from_parse,
-			action_history = lamb.node.History.from_parse
-		)
-
-		# Maximum amount of reductions.
-		# If None, no maximum is enforced.
-		# Must be at least 1.
-		self.reduction_limit: int | None = 1_000_000
-
-		# Ensure bound variables are unique.
-		# This is automatically incremented whenever we make
-		# a bound variable.
-		self.bound_variable_counter = 0
-
-		# Update iteration after this many iterations
-		# Make sure every place value has a non-zero digit
-		# so that all digits appear to be changing.
-		self.iter_update = 231
-
-		self.history: list[lamb.node.Root] = []
-
-	def prompt(self):
-		return self.prompt_session.prompt(
-			message = self.prompt_message
-		)
-
-	def parse(self, line) -> tuple[lamb.node.Root | MacroDef | Command, dict]:
-		e = self.parser.parse_line(line)
-
-		o = {}
-		if isinstance(e, MacroDef):
-			e.expr = lamb.node.Root(e.expr)
-			e.set_runner(self)
-			o = lamb.node.prepare(e.expr, ban_macro_name = e.label)
-		elif isinstance(e, lamb.node.Node):
-			e = lamb.node.Root(e)
-			e.set_runner(self)
-			o = lamb.node.prepare(e)
-
-		return e, o
-
-
-	def reduce(self, node: lamb.node.Root, *, status = {}) -> None:
-
-		warning_text = []
-
-		# Reduction Counter.
-		# We also count macro (and church) expansions,
-		# and subtract those from the final count.
-		k = 0
-		macro_expansions = 0
-
-		stop_reason = StopReason.MAX_EXCEEDED
-		start_time = time.time()
-		out_text = []
-
-		if status["has_history"] and len(self.history) != 0:
-			warning_text += [
-				("class:code", "$"),
-				("class:warn", " will be expanded to "),
-				("class:code", str(self.history[-1])),
-				("class:warn", "\n")
-			]
-
-		only_macro = (
-			isinstance(node.left, lamb.node.Macro) or
-			isinstance(node.left, lamb.node.Church)
-		)
-		if only_macro:
-			stop_reason = StopReason.SHOW_MACRO
-		m, node = lamb.node.expand(node, force_all = only_macro)
-		macro_expansions += m
-
-
-		for i in status["free_variables"]:
-			warning_text += [
-				("class:warn", "Name "),
-				("class:code", i),
-				("class:warn", " is a free variable\n"),
-			]
-
-		if len(warning_text) != 0:
-			printf(FormattedText(warning_text), style = lamb.utils.style)
-
-
-		while (
-				(
-					(self.reduction_limit is None) or
-					(k < self.reduction_limit)
-				) and not only_macro
-			):
-
-			# Show reduction count
-			if (k >= self.iter_update) and (k % self.iter_update == 0):
-				print(f" Reducing... {k:,}", end = "\r")
-
-			try:
-				red_type, node = lamb.node.reduce(node)
-			except KeyboardInterrupt:
-				stop_reason = StopReason.INTERRUPT
-				break
-
-			# If we can't reduce this expression anymore,
-			# it's in beta-normal form.
-			if red_type == lamb.node.ReductionType.NOTHING:
-				stop_reason = StopReason.BETA_NORMAL
-				break
-
-			# Count reductions
-			k += 1
-			if red_type == lamb.node.ReductionType.FUNCTION_APPLY:
-				macro_expansions += 1
-
-		if k >= self.iter_update:
-			# Clear reduction counter if it was printed
-			print(" " * round(14 + math.log10(k)), end = "\r")
-
-		if only_macro:
-			out_text += [
-				("class:ok", f"Displaying macro content")
-			]
-
-		else:
-			out_text += [
-				("class:ok", f"Runtime: "),
-				("class:text", f"{time.time() - start_time:.03f} seconds"),
-
-				("class:ok", f"\nExit reason: "),
-				stop_reason.value,
-
-				("class:ok", f"\nMacro expansions: "),
-				("class:text", f"{macro_expansions:,}"),
-
-				("class:ok", f"\nReductions: "),
-				("class:text", f"{k:,}\t"),
-				("class:muted", f"(Limit: {self.reduction_limit:,})")
-			]
-
-		if (
-				stop_reason == StopReason.BETA_NORMAL or
-				stop_reason == StopReason.LOOP_DETECTED or
-				only_macro
-		):
-			out_text += [
-				("class:ok", "\n\n    => "),
-				("class:text", str(node)), # type: ignore
-			]
-
-			self.history.append(lamb.node.expand(node, force_all = True)[1])
-
-
-		printf(
-			FormattedText(out_text),
-			style = lamb.utils.style
-		)
-
-	def save_macro(
-			self,
-			macro: MacroDef,
-			*,
-			silent = False
-		) -> None:
-		was_rewritten = macro.label in self.macro_table
-		self.macro_table[macro.label] = macro.expr
-
-		if not silent:
-			printf(FormattedText([
-				("class:text", "Set "),
-				("class:code", macro.label),
-				("class:text", " to "),
-				("class:code", str(macro.expr))
-			]), style = lamb.utils.style)
-
-	# Apply a list of definitions
-	def run(
-			self,
-			line: str,
-			*,
-			silent = False
-		) -> None:
-		e, o = self.parse(line)
-
-		# If this line is a macro definition, save the macro.
-		if isinstance(e, MacroDef):
-			self.save_macro(e, silent = silent)
-
-		# If this line is a command, do the command.
-		elif isinstance(e, Command):
-			if e.name not in lamb.commands.commands:
-				printf(
-					FormattedText([
-						("class:warn", f"Unknown command \"{e.name}\"")
-					]),
-					style = lamb.utils.style
-				)
-			else:
-				lamb.commands.commands[e.name](e, self)
-
-		# If this line is a plain expression, reduce it.
-		elif isinstance(e, lamb.node.Node):
-			self.reduce(e, status = o)
-
-		# We shouldn't ever get here.
-		else:
-			raise TypeError(f"I don't know what to do with a {type(e)}")
-
-
-	def run_lines(self, lines: list[str]):
-		for l in lines:
-			self.run(l, silent = True)

lamb/utils.py

@@ -1,93 +0,0 @@
-from prompt_toolkit.styles import Style
-from prompt_toolkit.formatted_text import HTML
-from prompt_toolkit import print_formatted_text as printf
-from importlib.metadata import version
-
-
-style = Style.from_dict({ # type: ignore
-	# Basic formatting
-	"text": "#FFFFFF",
-	"warn": "#FFA700",
-	"err": "#FF3809",
-	"prompt": "#05CFFF",
-	"ok": "#00EF7C",
-	"code": "#AAAAAA italic",
-	"muted": "#AAAAAA",
-
-	# Command formatting
-	# cmd_h:    section titles
-	# cmd_key:  keyboard keys, usually one character
-	"cmd_h": "#FF3809 bold",
-	"cmd_key": "#00EF7C bold",
-
-	# Only used in greeting
-	"_v": "#00EF7C bold",
-	"_l": "#FF3809 bold",
-	"_s": "#00EF7C bold",
-	"_p": "#AAAAAA"
-})
-
-
-def show_greeting():
-	#   |  _.._ _.|_
-	#   |_(_|| | ||_)
-	#       0.0.0
-	#
-	#       __  __
-	#    ,-`  ``  `,
-	#   (`   \      )
-	#  (`     \     `)
-	#  (,    / \    _)
-	#   (`  /   \   )
-	#    `'._.--._.'
-	#
-	# A λ calculus engine
-
-	printf(HTML("\n".join([
-		"",
-		"<_h>    |  _.._ _.|_",
-		"    |_(_|| | ||_)</_h>",
-		f"        <_v>{version('lamb')}</_v>",
-		"        __  __",
-		"     ,-`  ``  `,",
-		"    (`   <_l>\\</_l>      )",
-		"   (`     <_l>\\</_l>     `)",
-		"   (,    <_l>/ \\</_l>    _)",
-		"    (`  <_l>/   \\</_l>   )",
-		"     `'._.--._.'",
-		"",
-		"<_s> A λ calculus engine</_s>",
-		"<_p> Type :help for help</_p>",
-		""
-	])), style = style)
-
-def subscript(num: int):
-	sub = {
-		"0": "₀",
-		"1": "₁",
-		"2": "₂",
-		"3": "₃",
-		"4": "₄",
-		"5": "₅",
-		"6": "₆",
-		"7": "₇",
-		"8": "₈",
-		"9": "₉"
-	}
-
-	sup = {
-		"0": "⁰",
-		"1": "¹",
-		"2": "²",
-		"3": "³",
-		"4": "⁴",
-		"5": "⁵",
-		"6": "⁶",
-		"7": "⁷",
-		"8": "⁸",
-		"9": "⁹"
-	}
-
-	return "".join(
-		[sup[x] for x in str(num)]
-	)

lamb_engine/__init__.py

@@ -0,0 +1,8 @@
+from . import utils
+from . import nodes
+from . import parser
+
+from .runner import Runner
+from .runner import StopReason
+
+from .__main__ import main

lamb_engine/__main__.py

@@ -0,0 +1,79 @@
+from prompt_toolkit import PromptSession
+from prompt_toolkit import print_formatted_text as printf
+from prompt_toolkit.formatted_text import FormattedText
+from prompt_toolkit.formatted_text import to_plain_text
+from pyparsing import exceptions as ppx
+import sys
+
+import lamb_engine
+
+def main():
+
+	lamb_engine.utils.show_greeting()
+
+
+	r = lamb_engine.Runner(
+		prompt_session = PromptSession(
+			style = lamb_engine.utils.style,
+			lexer = lamb_engine.utils.LambdaLexer(),
+			key_bindings = lamb_engine.utils.bindings
+		),
+		prompt_message = FormattedText([
+			("class:prompt", "==> ")
+		])
+	)
+
+	# Load files passed as arguments
+	if len(sys.argv) > 1:
+		for i in range(1, len(sys.argv)):
+			try:
+				printf(FormattedText([
+					("class:warn", "\nLoading file "),
+					("class:code", sys.argv[i]),
+				]), style = lamb_engine.utils.style)
+				r.run(":load " + sys.argv[i])
+			except:
+				printf(FormattedText([
+					("class:err", "Error. Does this file exist?"),
+				]), style = lamb_engine.utils.style)
+
+		print("")
+
+	while True:
+		try:
+			i = r.prompt()
+
+		# Catch Ctrl-C and Ctrl-D
+		except KeyboardInterrupt:
+			printf("\n\nGoodbye.\n")
+			break
+		except EOFError:
+			printf("\n\nGoodbye.\n")
+			break
+
+		# Skip empty lines
+		if i.strip() == "":
+			continue
+
+		# Try to run an input line.
+		# Catch parse errors and point them out.
+		try:
+			x = r.run(i)
+		except ppx.ParseException as e:
+			l = len(to_plain_text(r.prompt_session.message))
+			printf(FormattedText([
+				("class:err", " "*(e.loc + l) + "^\n"),
+				("class:err", f"Syntax error at char {e.loc}."),
+				("class:text", "\n")
+			]), style = lamb_engine.utils.style)
+			continue
+		except lamb_engine.nodes.ReductionError as e:
+			printf(FormattedText([
+				("class:err", f"{e.msg}\n")
+			]), style = lamb_engine.utils.style)
+			continue
+
+		printf("")
+
+if __name__ == "__main__":
+	main()

lamb_engine/nodes/__init__.py

@@ -0,0 +1,3 @@
+from .misc import *
+from .nodes import *
+from .functions import *

lamb_engine/nodes/functions.py

@@ -0,0 +1,287 @@
+import lamb_engine
+import lamb_engine.nodes as lbn
+
+def print_node(node: lbn.Node, *, export: bool = False) -> str:
+	if not isinstance(node, lbn.Node):
+		raise TypeError(f"I don't know how to print a {type(node)}")
+
+	out = ""
+
+	bound_subs = {}
+
+	for s, n in node:
+		if isinstance(n, lbn.EndNode):
+			if isinstance(n, lbn.Bound):
+				out += bound_subs[n.identifier]
+			else:
+				out += n.print_value(export = export)
+
+		elif isinstance(n, lbn.Func):
+			# This should never be true, but
+			# keep this here to silence type checker.
+			if not isinstance(n.input, lbn.Bound):
+				raise Exception("input is macro, something is wrong.")
+
+			if s == lbn.Direction.UP:
+				o = n.input.print_value(export = export)
+				if o in bound_subs.values():
+					i = -1
+					p = o
+					while o in bound_subs.values():
+						o = p + lamb_engine.utils.subscript(i := i + 1)
+					bound_subs[n.input.identifier] = o
+				else:
+					bound_subs[n.input.identifier] = n.input.print_value()
+
+				if isinstance(n.parent, lbn.Call):
+					out += "("
+
+				if isinstance(n.parent, lbn.Func):
+					out += bound_subs[n.input.identifier]
+				else:
+					out += "λ" + bound_subs[n.input.identifier]
+				if not isinstance(n.left, lbn.Func):
+					out += "."
+
+			elif s == lbn.Direction.LEFT:
+				if isinstance(n.parent, lbn.Call):
+					out += ")"
+				del bound_subs[n.input.identifier]
+
+		elif isinstance(n, lbn.Call):
+			if s == lbn.Direction.UP:
+				out += "("
+			elif s == lbn.Direction.LEFT:
+				out += " "
+			elif s == lbn.Direction.RIGHT:
+				out += ")"
+
+	return out
+
+
+def clone(node: lbn.Node):
+	if not isinstance(node, lbn.Node):
+		raise TypeError(f"I don't know what to do with a {type(node)}")
+
+	macro_map = {}
+	if isinstance(node, lbn.Func):
+		c = node.copy()
+		macro_map[node.input.identifier] = c.input.identifier # type: ignore
+	else:
+		c = node.copy()
+
+	out = c
+	out_ptr = out # Stays one step behind ptr, in the new tree.
+	ptr = node
+	from_side = lbn.Direction.UP
+
+
+	if isinstance(node, lbn.EndNode):
+		return out
+
+	# We're not using a TreeWalker here because
+	# we need more control over our pointer when cloning.
+	while True:
+		if isinstance(ptr, lbn.EndNode):
+			from_side, ptr = ptr.go_up()
+			_, out_ptr = out_ptr.go_up()
+		elif isinstance(ptr, lbn.Func) or isinstance(ptr, lbn.Root):
+			if from_side == lbn.Direction.UP:
+				from_side, ptr = ptr.go_left()
+
+				if isinstance(ptr, lbn.Func):
+					c = ptr.copy()
+					macro_map[ptr.input.identifier] = c.input.identifier # type: ignore
+				elif isinstance(ptr, lbn.Bound):
+					c = ptr.copy()
+					if c.identifier in macro_map:
+						c.identifier = macro_map[c.identifier]
+				else:
+					c = ptr.copy()
+				out_ptr.set_side(ptr.parent_side, c)
+
+				_, out_ptr = out_ptr.go_left()
+			elif from_side == lbn.Direction.LEFT:
+				from_side, ptr = ptr.go_up()
+				_, out_ptr = out_ptr.go_up()
+		elif isinstance(ptr, lbn.Call):
+			if from_side == lbn.Direction.UP:
+				from_side, ptr = ptr.go_left()
+
+				if isinstance(ptr, lbn.Func):
+					c = ptr.copy()
+					macro_map[ptr.input.identifier] = c.input.identifier # type: ignore
+				elif isinstance(ptr, lbn.Bound):
+					c = ptr.copy()
+					if c.identifier in macro_map:
+						c.identifier = macro_map[c.identifier]
+				else:
+					c = ptr.copy()
+				out_ptr.set_side(ptr.parent_side, c)
+
+				_, out_ptr = out_ptr.go_left()
+			elif from_side == lbn.Direction.LEFT:
+				from_side, ptr = ptr.go_right()
+
+				if isinstance(ptr, lbn.Func):
+					c = ptr.copy()
+					macro_map[ptr.input.identifier] = c.input.identifier # type: ignore
+				elif isinstance(ptr, lbn.Bound):
+					c = ptr.copy()
+					if c.identifier in macro_map:
+						c.identifier = macro_map[c.identifier]
+				else:
+					c = ptr.copy()
+				out_ptr.set_side(ptr.parent_side, c)
+
+				_, out_ptr = out_ptr.go_right()
+			elif from_side == lbn.Direction.RIGHT:
+				from_side, ptr = ptr.go_up()
+				_, out_ptr = out_ptr.go_up()
+
+		if ptr is node.parent:
+			break
+	return out
+
+def prepare(root: lbn.Root, *, ban_macro_name = None) -> list:
+	"""
+	Prepare an expression for expansion.
+	This will does the following:
+		- Binds variables
+		- Turns unbound macros into free variables
+		- Generates warnings
+	"""
+
+	if not isinstance(root, lbn.Root):
+		raise TypeError(f"I don't know what to do with a {type(root)}")
+
+	bound_variables = {}
+
+	warnings = []
+
+	it = iter(root)
+	for s, n in it:
+		if isinstance(n, lbn.History):
+			if root.runner.history[0] == None:
+				raise lbn.ReductionError("There isn't any history to reference.")
+			else:
+				warnings += [
+					("class:code", "$"),
+					("class:warn", " will be expanded to ")
+				] + lamb_engine.utils.lex_str(str(n.expand()[1]))
+
+		# If this expression is part of a macro,
+		# make sure we don't reference it inside itself.
+		elif isinstance(n, lbn.Macro):
+			if (n.name == ban_macro_name) and (ban_macro_name is not None):
+				raise lbn.ReductionError("Macro cannot reference self")
+
+			# Bind variables
+			if n.name in bound_variables:
+				n.parent.set_side(
+					n.parent_side,
+					clone(bound_variables[n.name])
+				)
+				it.ptr = n.parent.get_side(n.parent_side)
+
+			# Turn undefined macros into free variables
+			elif n.name not in root.runner.macro_table:
+				warnings += [
+					("class:warn", "Name "),
+					("class:code", n.name),
+					("class:warn", " is a free variable\n"),
+				]
+				n.parent.set_side(
+					n.parent_side,
+					n.to_freevar()
+				)
+				it.ptr = n.parent.get_side(n.parent_side)
+
+
+		# Save bound variables when we enter a function's sub-tree,
+		# delete them when we exit it.
+		elif isinstance(n, lbn.Func):
+			if s == lbn.Direction.UP:
+				# Add this function's input to the table of bound variables.
+				# If it is already there, raise an error.
+				if (n.input.name in bound_variables):
+					raise lbn.ReductionError(f"Bound variable name conflict: \"{n.input.name}\"")
+				else:
+					bound_variables[n.input.name] = lbn.Bound(
+						lamb_engine.utils.remove_sub(n.input.name),
+						macro_name = n.input.name
+					)
+					n.input = bound_variables[n.input.name]
+
+			elif s == lbn.Direction.LEFT:
+				del bound_variables[n.input.macro_name] # type: ignore
+
+	return warnings
+
+# Apply a function.
+# Returns the function's output.
+def call_func(fn: lbn.Func, arg: lbn.Node):
+	for s, n in fn:
+		if isinstance(n, lbn.Bound) and (s == lbn.Direction.UP):
+			if n == fn.input:
+				if n.parent is None:
+					raise Exception("Tried to substitute a None bound variable.")
+
+				n.parent.set_side(n.parent_side, clone(arg)) # type: ignore
+	return fn.left
+
+# Do a single reduction step
+def reduce(root: lbn.Root) -> tuple[lbn.ReductionType, lbn.Root]:
+	if not isinstance(root, lbn.Root):
+		raise TypeError(f"I can't reduce a {type(root)}")
+
+	out = root
+	for s, n in out:
+		if isinstance(n, lbn.Call) and (s == lbn.Direction.UP):
+			if isinstance(n.left, lbn.Func):
+				n.parent.set_side(
+					n.parent_side, # type: ignore
+					call_func(n.left, n.right)
+				)
+
+				return lbn.ReductionType.FUNCTION_APPLY, out
+
+			elif isinstance(n.left, lbn.ExpandableEndNode):
+				r, n.left = n.left.expand()
+				return r, out
+	return lbn.ReductionType.NOTHING, out
+
+
+def expand(root: lbn.Root, *, force_all = False) -> tuple[int, lbn.Root]:
+	"""
+	Expands expandable nodes in the given tree.
+
+	If force_all is false, this only expands
+	ExpandableEndnodes that have "always_expand" set to True.
+
+	If force_all is True, this expands ALL
+	ExpandableEndnodes.
+	"""
+
+	if not isinstance(root, lbn.Root):
+		raise TypeError(f"I don't know what to do with a {type(root)}")
+
+	out = root
+	macro_expansions = 0
+
+	it = iter(root)
+	for s, n in it:
+		if (
+				isinstance(n, lbn.ExpandableEndNode) and
+				(force_all or n.always_expand)
+			):
+
+			n.parent.set_side(
+				n.parent_side, # type: ignore
+				n.expand()[1]
+			)
+			it.ptr = n.parent.get_side(
+				n.parent_side # type: ignore
+			)
+			macro_expansions += 1
+	return macro_expansions, out

lamb_engine/nodes/misc.py

@@ -0,0 +1,44 @@
+import enum
+
+class Direction(enum.Enum):
+	UP		= enum.auto()
+	LEFT	= enum.auto()
+	RIGHT	= enum.auto()
+
+
+class ReductionType(enum.Enum):
+	# Nothing happened. This implies that
+	# an expression cannot be reduced further.
+	NOTHING			= enum.auto()
+
+	# We replaced a macro with an expression.
+	MACRO_EXPAND	= enum.auto()
+
+	# We expanded a history reference
+	HIST_EXPAND 	= enum.auto()
+
+	# We turned a church numeral into an expression
+	AUTOCHURCH		= enum.auto()
+
+	# We applied a function.
+	# This is the only type of "formal" reduction step.
+	FUNCTION_APPLY	= enum.auto()
+
+# Pretty, short names for each reduction type.
+# These should all have the same length.
+reduction_text = {
+	ReductionType.NOTHING:			"N",
+	ReductionType.MACRO_EXPAND:		"M",
+	ReductionType.HIST_EXPAND:		"H",
+	ReductionType.AUTOCHURCH:		"C",
+	ReductionType.FUNCTION_APPLY:	"F",
+}
+
+class ReductionError(Exception):
+	"""
+	Raised when we encounter an error while reducing.
+
+	These should be caught and elegantly presented to the user.
+	"""
+	def __init__(self, msg: str):
+		self.msg = msg

lamb_engine/nodes/nodes.py

@@ -1,37 +1,5 @@
-import enum
+import lamb_engine
-import lamb
+import lamb_engine.nodes as lbn
-
-class Direction(enum.Enum):
-	UP		= enum.auto()
-	LEFT	= enum.auto()
-	RIGHT	= enum.auto()
-
-class ReductionType(enum.Enum):
-	# Nothing happened. This implies that
-	# an expression cannot be reduced further.
-	NOTHING			= enum.auto()
-
-	# We replaced a macro with an expression.
-	MACRO_EXPAND	= enum.auto()
-
-	# We expanded a history reference
-	HIST_EXPAND 	= enum.auto()
-
-	# We turned a church numeral into an expression
-	AUTOCHURCH		= enum.auto()
-
-	# We applied a function.
-	# This is the only type of "formal" reduction step.
-	FUNCTION_APPLY	= enum.auto()
-
-class ReductionError(Exception):
-	"""
-	Raised when we encounter an error while reducing.
-
-	These should be caught and elegantly presented to the user.
-	"""
-	def __init__(self, msg: str):
-		self.msg = msg
 
 class TreeWalker:
 	"""
@@ -48,7 +16,7 @@ class TreeWalker:
 		self.expr = expr
 		self.ptr = expr
 		self.first_step = True
-		self.from_side = Direction.UP
+		self.from_side = lbn.Direction.UP
 
 	def __iter__(self):
 		return self
@@ -64,21 +32,21 @@ class TreeWalker:
 			return self.from_side, self.ptr
 
 		if isinstance(self.ptr, Root):
-			if self.from_side == Direction.UP:
+			if self.from_side == lbn.Direction.UP:
 				self.from_side, self.ptr = self.ptr.go_left()
 		elif isinstance(self.ptr, EndNode):
 			self.from_side, self.ptr = self.ptr.go_up()
 		elif isinstance(self.ptr, Func):
-			if self.from_side == Direction.UP:
+			if self.from_side == lbn.Direction.UP:
 				self.from_side, self.ptr = self.ptr.go_left()
-			elif self.from_side == Direction.LEFT:
+			elif self.from_side == lbn.Direction.LEFT:
 				self.from_side, self.ptr = self.ptr.go_up()
 		elif isinstance(self.ptr, Call):
-			if self.from_side == Direction.UP:
+			if self.from_side == lbn.Direction.UP:
 				self.from_side, self.ptr = self.ptr.go_left()
-			elif self.from_side == Direction.LEFT:
+			elif self.from_side == lbn.Direction.LEFT:
 				self.from_side, self.ptr = self.ptr.go_right()
-			elif self.from_side == Direction.RIGHT:
+			elif self.from_side == lbn.Direction.RIGHT:
 				self.from_side, self.ptr = self.ptr.go_up()
 		else:
 			raise TypeError(f"I don't know how to iterate a {type(self.ptr)}")
@@ -109,12 +77,12 @@ class Node:
 		self.parent_side: Direction = None # type: ignore
 
 		# Left and right nodes, None if empty
-		self._left: Node | None = None
+		self._left = None
-		self._right: Node | None = None
+		self._right = None
 
 		# The runner this node is attached to.
 		# Set by Node.set_runner()
-		self.runner: lamb.runner.Runner = None # type: ignore
+		self.runner: lamb_engine.runner.Runner = None # type: ignore
 
 	def __iter__(self):
 		return TreeWalker(self)
@@ -127,9 +95,9 @@ class Node:
 		"""
 
 		if (parent is not None) and (side is None):
-			raise Exception("If a node has a parent, it must have a direction.")
+			raise Exception("If a node has a parent, it must have a lbn.direction.")
 		if (parent is None) and (side is not None):
-			raise Exception("If a node has no parent, it cannot have a direction.")
+			raise Exception("If a node has no parent, it cannot have a lbn.direction.")
 		self.parent = parent
 		self.parent_side = side
 		return self
@@ -141,7 +109,7 @@ class Node:
 	@left.setter
 	def left(self, node):
 		if node is not None:
-			node._set_parent(self, Direction.LEFT)
+			node._set_parent(self, lbn.Direction.LEFT)
 		self._left = node
 
 	@property
@@ -151,27 +119,27 @@ class Node:
 	@right.setter
 	def right(self, node):
 		if node is not None:
-			node._set_parent(self, Direction.RIGHT)
+			node._set_parent(self, lbn.Direction.RIGHT)
 		self._right = node
 
 
-	def set_side(self, side: Direction, node):
+	def set_side(self, side: lbn.Direction, node):
 		"""
 		A wrapper around Node.left and Node.right that
 		automatically selects a side.
 		"""
 
-		if side == Direction.LEFT:
+		if side == lbn.Direction.LEFT:
 			self.left = node
-		elif side == Direction.RIGHT:
+		elif side == lbn.Direction.RIGHT:
 			self.right = node
 		else:
 			raise TypeError("Can only set left or right side.")
 
-	def get_side(self, side: Direction):
+	def get_side(self, side: lbn.Direction):
-		if side == Direction.LEFT:
+		if side == lbn.Direction.LEFT:
 			return self.left
-		elif side == Direction.RIGHT:
+		elif side == lbn.Direction.RIGHT:
 			return self.right
 		else:
 			raise TypeError("Can only get left or right side.")
@@ -188,7 +156,7 @@ class Node:
 
 		if self._left is None:
 			raise Exception("Can't go left when left is None")
-		return Direction.UP, self._left
+		return lbn.Direction.UP, self._left
 
 	def go_right(self):
 		"""
@@ -200,7 +168,7 @@ class Node:
 		"""
 		if self._right is None:
 			raise Exception("Can't go right when right is None")
-		return Direction.UP, self._right
+		return lbn.Direction.UP, self._right
 
 	def go_up(self):
 		"""
@@ -221,17 +189,17 @@ class Node:
 		raise NotImplementedError("Nodes MUST provide a `copy` method!")
 
 	def __str__(self) -> str:
-		return print_node(self)
+		return lbn.print_node(self)
 
 	def export(self) -> str:
 		"""
 		Convert this tree to a parsable string.
 		"""
-		return print_node(self, export = True)
+		return lbn.print_node(self, export = True)
 
 	def set_runner(self, runner):
 		for s, n in self:
-			if s == Direction.UP:
+			if s == lbn.Direction.UP:
 				n.runner = runner # type: ignore
 		return self
 
@@ -241,7 +209,7 @@ class EndNode(Node):
 
 class ExpandableEndNode(EndNode):
 	always_expand = False
-	def expand(self) -> tuple[ReductionType, Node]:
+	def expand(self) -> tuple[lbn.ReductionType, Node]:
 		raise NotImplementedError("ExpandableEndNodes MUST provide an `expand` method!")
 
 class FreeVar(EndNode):
@@ -280,13 +248,13 @@ class Macro(ExpandableEndNode):
 	def print_value(self, *, export: bool = False) -> str:
 		return self.name
 
-	def expand(self) -> tuple[ReductionType, Node]:
+	def expand(self) -> tuple[lbn.ReductionType, Node]:
 		if self.name in self.runner.macro_table:
 			# The element in the macro table will be a Root node,
 			# so we clone its left element.
 			return (
-				ReductionType.MACRO_EXPAND,
+				lbn.ReductionType.MACRO_EXPAND,
-				clone(self.runner.macro_table[self.name].left)
+				lbn.clone(self.runner.macro_table[self.name].left)
 			)
 		else:
 			raise Exception(f"Macro {self.name} is not defined")
@@ -315,16 +283,16 @@ class Church(ExpandableEndNode):
 	def print_value(self, *, export: bool = False) -> str:
 		return str(self.value)
 
-	def expand(self) -> tuple[ReductionType, Node]:
+	def expand(self) -> tuple[lbn.ReductionType, Node]:
 		f = Bound("f")
 		a = Bound("a")
 		chain = a
 
 		for i in range(self.value):
-			chain = Call(clone(f), clone(chain))
+			chain = Call(lbn.clone(f), lbn.clone(chain))
 
 		return (
-			ReductionType.AUTOCHURCH,
+			lbn.ReductionType.AUTOCHURCH,
 			Func(f, Func(a, chain)).set_runner(self.runner)
 		)
 
@@ -350,24 +318,31 @@ class History(ExpandableEndNode):
 	def print_value(self, *, export: bool = False) -> str:
 		return "$"
 
-	def expand(self) -> tuple[ReductionType, Node]:
+	def expand(self) -> tuple[lbn.ReductionType, Node]:
-		if len(self.runner.history) == 0:
+		# We shouldn't ever get here, prepare()
-			raise ReductionError(f"There isn't any history to reference.")
+		# catches empty history.
+		if self.runner.history[0] == None:
+			raise Exception(f"Tried to expand empty history.")
 		# .left is VERY important!
 		# self.runner.history will contain Root nodes,
 		# and we don't want those *inside* our tree.
-		return ReductionType.HIST_EXPAND, clone(self.runner.history[-1].left)
+		return lbn.ReductionType.HIST_EXPAND, lbn.clone(self.runner.history[0].left)
 
 	def copy(self):
 		return History(runner = self.runner)
 
 bound_counter = 0
 class Bound(EndNode):
-	def __init__(self, name: str, *, forced_id = None, runner = None):
+	def __init__(self, name: str, *, forced_id = None, runner = None, macro_name = None):
 		self.name = name
 		global bound_counter
 		self.runner = runner # type: ignore
 
+		# The name of the macro this bound came from.
+		# Always equal to self.name, unless the macro
+		# this came from had a subscript.
+		self.macro_name = macro_name
+
 		if forced_id is None:
 			self.identifier = bound_counter
 			bound_counter += 1
@@ -375,7 +350,11 @@ class Bound(EndNode):
 			self.identifier = forced_id
 
 	def copy(self):
-		return Bound(self.name, forced_id = self.identifier, runner = self.runner)
+		return Bound(
+			self.name,
+			forced_id = self.identifier,
+			runner = self.runner
+		)
 
 	def __eq__(self, other):
 		if not isinstance(other, Bound):
@@ -402,9 +381,9 @@ class Func(Node):
 				Func.from_parse(result)
 			)
 
-	def __init__(self, input: Macro | Bound, output: Node, *, runner = None) -> None:
+	def __init__(self, input, output: Node, *, runner = None) -> None:
 		super().__init__()
-		self.input: Macro | Bound = input
+		self.input = input
 		self.left: Node = output
 		self.right: None = None
 		self.runner = runner # type: ignore
@@ -413,7 +392,14 @@ class Func(Node):
 		return f"<func {self.input!r} {self.left!r}>"
 
 	def copy(self):
-		return Func(self.input, None, runner = self.runner) # type: ignore
+		return Func(
+			Bound(
+				self.input.name,
+				runner = self.runner
+			),
+			None, # type: ignore
+			runner = self.runner
+		)
 
 class Root(Node):
 	"""
@@ -463,226 +449,4 @@ class Call(Node):
 		return f"<call {self.left!r} {self.right!r}>"
 
 	def copy(self):
-		return Call(None, None, runner = self.runner) # type: ignore
+		return Call(None, None, runner = self.runner) # type: ignore
-
-
-def print_node(node: Node, *, export: bool = False) -> str:
-	if not isinstance(node, Node):
-		raise TypeError(f"I don't know how to print a {type(node)}")
-
-	out = ""
-
-	bound_subs = {}
-
-	for s, n in node:
-		if isinstance(n, EndNode):
-			if isinstance(n, Bound):
-				if n.identifier not in bound_subs.keys():
-					o = n.print_value(export = export)
-					if o in bound_subs.items():
-						i = 1
-						while o in bound_subs.items():
-							o = lamb.utils.subscript(i := i + 1)
-						bound_subs[n.identifier] = o
-					else:
-						bound_subs[n.identifier] = n.print_value()
-
-
-				out += bound_subs[n.identifier]
-			else:
-				out += n.print_value(export = export)
-
-		elif isinstance(n, Func):
-			if s == Direction.UP:
-				if isinstance(n.parent, Func):
-					out += n.input.name
-				else:
-					out += "λ" + n.input.name
-				if not isinstance(n.left, Func):
-					out += "."
-
-		elif isinstance(n, Call):
-			if s == Direction.UP:
-				out += "("
-			elif s == Direction.LEFT:
-				out += " "
-			elif s == Direction.RIGHT:
-				out += ")"
-
-	return out
-
-def clone(node: Node):
-	if not isinstance(node, Node):
-		raise TypeError(f"I don't know what to do with a {type(node)}")
-
-	out = node.copy()
-	out_ptr = out # Stays one step behind ptr, in the new tree.
-	ptr = node
-	from_side = Direction.UP
-
-	if isinstance(node, EndNode):
-		return out
-
-	# We're not using a TreeWalker here because
-	# we need more control over our pointer when cloning.
-	while True:
-		if isinstance(ptr, EndNode):
-			from_side, ptr = ptr.go_up()
-			_, out_ptr = out_ptr.go_up()
-		elif isinstance(ptr, Func) or isinstance(ptr, Root):
-			if from_side == Direction.UP:
-				from_side, ptr = ptr.go_left()
-				out_ptr.set_side(ptr.parent_side, ptr.copy())
-				_, out_ptr = out_ptr.go_left()
-			elif from_side == Direction.LEFT:
-				from_side, ptr = ptr.go_up()
-				_, out_ptr = out_ptr.go_up()
-		elif isinstance(ptr, Call):
-			if from_side == Direction.UP:
-				from_side, ptr = ptr.go_left()
-				out_ptr.set_side(ptr.parent_side, ptr.copy())
-				_, out_ptr = out_ptr.go_left()
-			elif from_side == Direction.LEFT:
-				from_side, ptr = ptr.go_right()
-				out_ptr.set_side(ptr.parent_side, ptr.copy())
-				_, out_ptr = out_ptr.go_right()
-			elif from_side == Direction.RIGHT:
-				from_side, ptr = ptr.go_up()
-				_, out_ptr = out_ptr.go_up()
-
-		if ptr is node.parent:
-			break
-	return out
-
-def prepare(root: Root, *, ban_macro_name = None) -> dict:
-	"""
-	Prepare an expression for expansion.
-	This will does the following:
-		- Binds variables
-		- Turns unbound macros into free variables
-		- Generates warnings
-	"""
-
-	if not isinstance(root, Root):
-		raise TypeError(f"I don't know what to do with a {type(root)}")
-
-	bound_variables = {}
-
-	output = {
-		"has_history": False,
-		"free_variables": set()
-	}
-
-	it = iter(root)
-	for s, n in it:
-		if isinstance(n, History):
-			output["has_history"] = True
-
-		# If this expression is part of a macro,
-		# make sure we don't reference it inside itself.
-		elif isinstance(n, Macro):
-			if (n.name == ban_macro_name) and (ban_macro_name is not None):
-				raise ReductionError("Macro cannot reference self")
-
-			# Bind variables
-			if n.name in bound_variables:
-				n.parent.set_side(
-					n.parent_side,
-					clone(bound_variables[n.name])
-				)
-				it.ptr = n.parent.get_side(n.parent_side)
-
-			# Turn undefined macros into free variables
-			elif n.name not in root.runner.macro_table:
-				output["free_variables"].add(n.name)
-				n.parent.set_side(
-					n.parent_side,
-					n.to_freevar()
-				)
-				it.ptr = n.parent.get_side(n.parent_side)
-
-
-		# Save bound variables when we enter a function's sub-tree,
-		# delete them when we exit it.
-		elif isinstance(n, Func):
-			if s == Direction.UP:
-				# Add this function's input to the table of bound variables.
-				# If it is already there, raise an error.
-				if (n.input.name in bound_variables):
-					raise ReductionError(f"Bound variable name conflict: \"{n.input.name}\"")
-				else:
-					bound_variables[n.input.name] = Bound(n.input.name)
-					n.input = bound_variables[n.input.name]
-
-			elif s == Direction.LEFT:
-				del bound_variables[n.input.name]
-
-	return output
-
-# Apply a function.
-# Returns the function's output.
-def call_func(fn: Func, arg: Node):
-	for s, n in fn:
-		if isinstance(n, Bound) and (s == Direction.UP):
-			if n == fn.input:
-				if n.parent is None:
-					raise Exception("Tried to substitute a None bound variable.")
-
-				n.parent.set_side(n.parent_side, clone(arg)) # type: ignore
-	return fn.left
-
-# Do a single reduction step
-def reduce(root: Root) -> tuple[ReductionType, Root]:
-	if not isinstance(root, Root):
-		raise TypeError(f"I can't reduce a {type(root)}")
-
-	out = root
-	for s, n in out:
-		if isinstance(n, Call) and (s == Direction.UP):
-			if isinstance(n.left, Func):
-				n.parent.set_side(
-					n.parent_side, # type: ignore
-					call_func(n.left, n.right)
-				)
-
-				return ReductionType.FUNCTION_APPLY, out
-
-			elif isinstance(n.left, ExpandableEndNode):
-				r, n.left = n.left.expand()
-				return r, out
-	return ReductionType.NOTHING, out
-
-
-def expand(root: Root, *, force_all = False) -> tuple[int, Root]:
-	"""
-	Expands expandable nodes in the given tree.
-
-	If force_all is false, this only expands
-	ExpandableEndnodes that have "always_expand" set to True.
-
-	If force_all is True, this expands ALL
-	ExpandableEndnodes.
-	"""
-
-	if not isinstance(root, Root):
-		raise TypeError(f"I don't know what to do with a {type(root)}")
-
-	out = root
-	macro_expansions = 0
-
-	it = iter(root)
-	for s, n in it:
-		if (
-				isinstance(n, ExpandableEndNode) and
-				(force_all or n.always_expand)
-			):
-
-			n.parent.set_side(
-				n.parent_side, # type: ignore
-				n.expand()[1]
-			)
-			it.ptr = n.parent.get_side(
-				n.parent_side # type: ignore
-			)
-			macro_expansions += 1
-	return macro_expansions, out

lamb_engine/parser.py

@@ -13,7 +13,7 @@ class LambdaParser:
 		# We still create macro objects from them, they are turned into
 		# bound variables after the expression is built.
 		self.pp_macro = pp.Word(pp.alphas + "_")
-		self.pp_bound = pp.Char(pp.srange("[a-z]"))
+		self.pp_bound = pp.Regex("[a-z][₀₁₂₃₄₅₆₈₉]*")
 		self.pp_name = self.pp_bound ^ self.pp_macro
 		self.pp_church = pp.Word(pp.nums)
 		self.pp_history = pp.Char("$")
@@ -56,7 +56,7 @@ class LambdaParser:
 			(self.lp + self.pp_history + self.rp)
 		)
 
-		self.pp_command = pp.Suppress(":") + pp.Word(pp.alphas + "_") + pp.Word(pp.alphas + pp.nums + "_")[0, ...]
+		self.pp_command = pp.Suppress(":") + pp.Word(pp.alphas + "_") + pp.Word(pp.printables)[0, ...]
 
 
 		self.pp_all = (

lamb_engine/runner/__init__.py

@@ -0,0 +1,2 @@
+from .runner import Runner
+from .runner import StopReason

lamb_engine/runner/commands.py

@@ -2,18 +2,19 @@ from prompt_toolkit.formatted_text import FormattedText
 from prompt_toolkit.formatted_text import HTML
 from prompt_toolkit import print_formatted_text as printf
 from prompt_toolkit.shortcuts import clear as clear_screen
+from prompt_toolkit import prompt
 
 import os.path
 from pyparsing import exceptions as ppx
 
-import lamb
+import lamb_engine
 
 commands = {}
 help_texts = {}
 
 def lamb_command(
 		*,
-		command_name: str | None = None,
+		command_name = None,
 		help_text: str
 	):
 	"""
@@ -27,6 +28,100 @@ def lamb_command(
 		help_texts[name] = help_text
 	return inner
 
+@lamb_command(
+	command_name = "step",
+	help_text = "Toggle step-by-step reduction"
+)
+def cmd_step(command, runner) -> None:
+	if len(command.args) > 1:
+		printf(
+			HTML(
+				f"<err>Command <code>:{command.name}</code> takes no more than one argument.</err>"
+			),
+			style = lamb_engine.utils.style
+		)
+		return
+
+	target = not runner.step_reduction
+	if len(command.args) == 1:
+		if command.args[0].lower() in ("y", "yes"):
+			target = True
+		elif command.args[0].lower() in ("n", "no"):
+			target = False
+		else:
+			printf(
+				HTML(
+					f"<err>Usage: <code>:step [yes|no]</code></err>"
+				),
+				style = lamb_engine.utils.style
+			)
+			return
+
+
+	if target:
+		printf(
+			HTML(
+				f"<warn>Enabled step-by-step reduction.</warn>"
+			),
+			style = lamb_engine.utils.style
+		)
+		runner.step_reduction = True
+	else:
+		printf(
+			HTML(
+				f"<warn>Disabled step-by-step reduction.</warn>"
+			),
+			style = lamb_engine.utils.style
+		)
+		runner.step_reduction = False
+
+@lamb_command(
+	command_name = "expand",
+	help_text = "Toggle full expansion"
+)
+def cmd_expand(command, runner) -> None:
+	if len(command.args) > 1:
+		printf(
+			HTML(
+				f"<err>Command <code>:{command.name}</code> takes no more than one argument.</err>"
+			),
+			style = lamb_engine.utils.style
+		)
+		return
+
+	target = not runner.full_expansion
+	if len(command.args) == 1:
+		if command.args[0].lower() in ("y", "yes"):
+			target = True
+		elif command.args[0].lower() in ("n", "no"):
+			target = False
+		else:
+			printf(
+				HTML(
+					f"<err>Usage: <code>:expand [yes|no]</code></err>"
+				),
+				style = lamb_engine.utils.style
+			)
+			return
+
+
+	if target:
+		printf(
+			HTML(
+				f"<warn>Enabled complete expansion.</warn>"
+			),
+			style = lamb_engine.utils.style
+		)
+		runner.full_expansion = True
+	else:
+		printf(
+			HTML(
+				f"<warn>Disabled complete expansion.</warn>"
+			),
+			style = lamb_engine.utils.style
+		)
+		runner.full_expansion = False
+
 
 @lamb_command(
 	command_name = "save",
@@ -38,17 +133,18 @@ def cmd_save(command, runner) -> None:
 			HTML(
 				f"<err>Command <code>:{command.name}</code> takes exactly one argument.</err>"
 			),
-			style = lamb.utils.style
+			style = lamb_engine.utils.style
 		)
 		return
 
 	target = command.args[0]
 	if os.path.exists(target):
-		confirm = runner.prompt_session.prompt(
+		confirm = prompt(
 			message = FormattedText([
 				("class:warn", "File exists. Overwrite? "),
 				("class:text", "[yes/no]: ")
-			])
+			]),
+			style = lamb_engine.utils.style
 		).lower()
 
 		if confirm != "yes":
@@ -56,7 +152,7 @@ def cmd_save(command, runner) -> None:
 				HTML(
 					"<err>Cancelled.</err>"
 				),
-				style = lamb.utils.style
+				style = lamb_engine.utils.style
 			)
 			return
 
@@ -69,7 +165,7 @@ def cmd_save(command, runner) -> None:
 		HTML(
 			f"Wrote {len(runner.macro_table)} macros to <code>{target}</code>"
 		),
-		style = lamb.utils.style
+		style = lamb_engine.utils.style
 	)
 
 
@@ -83,7 +179,7 @@ def cmd_load(command, runner):
 			HTML(
 				f"<err>Command <code>:{command.name}</code> takes exactly one argument.</err>"
 			),
-			style = lamb.utils.style
+			style = lamb_engine.utils.style
 		)
 		return
 
@@ -93,7 +189,7 @@ def cmd_load(command, runner):
 			HTML(
 				f"<err>File {target} doesn't exist.</err>"
 			),
-			style = lamb.utils.style
+			style = lamb_engine.utils.style
 		)
 		return
 
@@ -101,7 +197,14 @@ def cmd_load(command, runner):
 		lines = [x.strip() for x in f.readlines()]
 
 	for i in range(len(lines)):
-		l = lines[i]
+		l = lines[i].strip()
+
+		# Skip comments and empty lines
+		if l.startswith("#"):
+			continue
+		if l == "":
+			continue
+
 		try:
 			x = runner.parse(l)[0]
 		except ppx.ParseException as e:
@@ -112,18 +215,18 @@ def cmd_load(command, runner):
 					("class:err", l[e.loc]),
 					("class:code", l[e.loc+1:])
 				]),
-				style = lamb.utils.style
+				style = lamb_engine.utils.style
 			)
 			return
 
-		if not isinstance(x, lamb.runner.MacroDef):
+		if not isinstance(x, lamb_engine.runner.runner.MacroDef):
 			printf(
 				FormattedText([
 					("class:warn", f"Skipping line {i+1:02}: "),
 					("class:code", l),
 					("class:warn", f" is not a macro definition.")
 				]),
-				style = lamb.utils.style
+				style = lamb_engine.utils.style
 			)
 			return
 
@@ -131,10 +234,9 @@ def cmd_load(command, runner):
 
 		printf(
 			FormattedText([
-				("class:ok", f"Loaded {x.label}: "),
+				("class:ok", f"Loaded {x.label}: ")
-				("class:code", str(x.expr))
+			] + lamb_engine.utils.lex_str(str(x.expr))),
-			]),
+			style = lamb_engine.utils.style
-			style = lamb.utils.style
 		)
 
 
@@ -147,7 +249,7 @@ def mdel(command, runner) -> None:
 			HTML(
 				f"<err>Command <code>:{command.name}</code> takes exactly one argument.</err>"
 			),
-			style = lamb.utils.style
+			style = lamb_engine.utils.style
 		)
 		return
 
@@ -157,33 +259,63 @@ def mdel(command, runner) -> None:
 			HTML(
 				f"<warn>Macro \"{target}\" is not defined</warn>"
 			),
-			style = lamb.utils.style
+			style = lamb_engine.utils.style
 		)
 		return
 
 	del runner.macro_table[target]
 
+@lamb_command(
+	help_text = "Delete all macros"
+)
+def delmac(command, runner) -> None:
+	confirm = prompt(
+		message = FormattedText([
+			("class:warn", "Are you sure? "),
+			("class:text", "[yes/no]: ")
+		]),
+		style = lamb_engine.utils.style
+	).lower()
+
+	if confirm != "yes":
+		printf(
+			HTML(
+				"<err>Cancelled.</err>"
+			),
+			style = lamb_engine.utils.style
+		)
+		return
+
+	runner.macro_table = {}
+
 
 @lamb_command(
 	help_text = "Show macros"
 )
 def macros(command, runner) -> None:
-	printf(FormattedText([
+	if len(runner.macro_table) == 0:
-			("class:cmd_h", "\nDefined Macros:\n"),
+		printf(FormattedText([
-		] +
+				("class:warn", "No macros are defined."),
-		[
+			]),
-			("class:text", f"\t{name} \t {exp}\n")
+			style = lamb_engine.utils.style
-			for name, exp in runner.macro_table.items()
+		)
-		]),
+	else:
-		style = lamb.utils.style
+		printf(FormattedText([
-	)
+				("class:cmd_h", "\nDefined Macros:\n"),
+			] +
+			[
+				("class:text", f"\t{name} \t {exp}\n")
+				for name, exp in runner.macro_table.items()
+			]),
+			style = lamb_engine.utils.style
+		)
 
 @lamb_command(
 	help_text = "Clear the screen"
 )
 def clear(command, runner) -> None:
 	clear_screen()
-	lamb.utils.show_greeting()
+	lamb_engine.utils.show_greeting()
 
 @lamb_command(
 	help_text = "Get or set reduction limit"
@@ -195,14 +327,14 @@ def rlimit(command, runner) -> None:
 				HTML(
 					"<ok>No reduction limit is set</ok>"
 				),
-				style = lamb.utils.style
+				style = lamb_engine.utils.style
 			)
 		else:
 			printf(
 				HTML(
 					f"<ok>Reduction limit is {runner.reduction_limit:,}</ok>"
 				),
-				style = lamb.utils.style
+				style = lamb_engine.utils.style
 			)
 		return
 
@@ -211,7 +343,7 @@ def rlimit(command, runner) -> None:
 			HTML(
 				f"<err>Command <code>:{command.name}</code> takes exactly one argument.</err>"
 			),
-			style = lamb.utils.style
+			style = lamb_engine.utils.style
 		)
 		return
 
@@ -222,7 +354,7 @@ def rlimit(command, runner) -> None:
 			HTML(
 				f"<ok>Removed reduction limit</ok>"
 			),
-			style = lamb.utils.style
+			style = lamb_engine.utils.style
 		)
 		return
 
@@ -233,7 +365,7 @@ def rlimit(command, runner) -> None:
 			HTML(
 				"<err>Reduction limit must be a positive integer or \"none\".</err>"
 			),
-			style = lamb.utils.style
+			style = lamb_engine.utils.style
 		)
 		return
 
@@ -242,7 +374,7 @@ def rlimit(command, runner) -> None:
 			HTML(
 				"<err>Reduction limit must be at least 50.</err>"
 			),
-			style = lamb.utils.style
+			style = lamb_engine.utils.style
 		)
 		return
 
@@ -251,7 +383,7 @@ def rlimit(command, runner) -> None:
 		HTML(
 			f"<ok>Set reduction limit to {t:,}</ok>"
 		),
-		style = lamb.utils.style
+		style = lamb_engine.utils.style
 	)
 
 
@@ -284,5 +416,5 @@ def help(command, runner) -> None:
 			"<muted>Detailed documentation can be found on this project's git page.</muted>" +
 			"</text>"
 		),
-		style = lamb.utils.style
+		style = lamb_engine.utils.style
 	)

lamb_engine/runner/misc.py

@@ -0,0 +1,42 @@
+import enum
+import lamb_engine
+
+class StopReason(enum.Enum):
+	BETA_NORMAL		= ("class:text", "β-normal form")
+	LOOP_DETECTED	= ("class:warn", "Loop detected")
+	MAX_EXCEEDED	= ("class:err", "Too many reductions")
+	INTERRUPT		= ("class:warn", "User interrupt")
+	SHOW_MACRO		= ("class:text", "Displaying macro content")
+
+class MacroDef:
+	@staticmethod
+	def from_parse(result):
+		return MacroDef(
+			result[0].name,
+			result[1]
+		)
+
+	def __init__(self, label: str, expr: lamb_engine.nodes.Node):
+		self.label = label
+		self.expr = expr
+
+	def __repr__(self):
+		return f"<{self.label} := {self.expr!r}>"
+
+	def __str__(self):
+		return f"{self.label} := {self.expr}"
+
+	def set_runner(self, runner):
+		return self.expr.set_runner(runner)
+
+class Command:
+	@staticmethod
+	def from_parse(result):
+		return Command(
+			result[0],
+			result[1:]
+		)
+
+	def __init__(self, name, args):
+		self.name = name
+		self.args = args

lamb_engine/runner/runner.py

@@ -0,0 +1,303 @@
+from prompt_toolkit import PromptSession
+from prompt_toolkit.formatted_text import FormattedText
+from prompt_toolkit.key_binding import KeyBindings
+from prompt_toolkit import prompt
+from prompt_toolkit import print_formatted_text as printf
+import collections
+import math
+import time
+
+import lamb_engine
+
+from lamb_engine.runner.misc import MacroDef
+from lamb_engine.runner.misc import Command
+from lamb_engine.runner.misc import StopReason
+from lamb_engine.runner import commands as cmd
+
+
+# Keybindings for step prompt.
+# Prevents any text from being input.
+step_bindings = KeyBindings()
+@step_bindings.add("<any>")
+def _(event):
+	pass
+
+
+class Runner:
+	def __init__(
+		self,
+		prompt_session: PromptSession,
+		prompt_message
+	):
+		self.macro_table = {}
+		self.prompt_session = prompt_session
+		self.prompt_message = prompt_message
+		self.parser = lamb_engine.parser.LambdaParser(
+			action_func = lamb_engine.nodes.Func.from_parse,
+			action_bound = lamb_engine.nodes.Macro.from_parse,
+			action_macro = lamb_engine.nodes.Macro.from_parse,
+			action_call = lamb_engine.nodes.Call.from_parse,
+			action_church = lamb_engine.nodes.Church.from_parse,
+			action_macro_def = MacroDef.from_parse,
+			action_command = Command.from_parse,
+			action_history = lamb_engine.nodes.History.from_parse
+		)
+
+		# Maximum amount of reductions.
+		# If None, no maximum is enforced.
+		# Must be at least 1.
+		self.reduction_limit = 1_000_000
+
+		# Ensure bound variables are unique.
+		# This is automatically incremented whenever we make
+		# a bound variable.
+		self.bound_variable_counter = 0
+
+		# Update iteration after this many iterations
+		# Make sure every place value has a non-zero digit
+		# so that all digits appear to be changing.
+		self.iter_update = 231
+
+		self.history = collections.deque(
+			[None] * 10,
+			10)
+
+
+		# If true, reduce step-by-step.
+		self.step_reduction = False
+
+		# If true, expand ALL macros when printing output
+		self.full_expansion = False
+
+	def prompt(self):
+		return self.prompt_session.prompt(
+			message = self.prompt_message
+		)
+
+	def parse(self, line): # -> tuple[lamb_engine.nodes.Root | MacroDef | Command, list]
+		e = self.parser.parse_line(line)
+
+		w = []
+		if isinstance(e, MacroDef):
+			e.expr = lamb_engine.nodes.Root(e.expr)
+			e.set_runner(self)
+			w = lamb_engine.nodes.prepare(e.expr, ban_macro_name = e.label)
+		elif isinstance(e, lamb_engine.nodes.Node):
+			e = lamb_engine.nodes.Root(e)
+			e.set_runner(self)
+			w = lamb_engine.nodes.prepare(e)
+
+		return e, w
+
+
+	def reduce(self, node: lamb_engine.nodes.Root, *, warnings = []) -> None:
+
+		# Reduction Counter.
+		# We also count macro (and church) expansions,
+		# and subtract those from the final count.
+		k = 0
+		macro_expansions = 0
+
+		stop_reason = StopReason.MAX_EXCEEDED
+		start_time = time.time()
+		out_text = []
+
+		only_macro = (
+			isinstance(node.left, lamb_engine.nodes.Macro) or
+			isinstance(node.left, lamb_engine.nodes.Church)
+		)
+		if only_macro:
+			stop_reason = StopReason.SHOW_MACRO
+		m, node = lamb_engine.nodes.expand(node, force_all = only_macro)
+		macro_expansions += m
+
+		if len(warnings) != 0:
+			printf(FormattedText(warnings), style = lamb_engine.utils.style)
+
+		if self.step_reduction:
+			printf(FormattedText([
+				("class:warn", "Step-by-step reduction is enabled.\n"),
+				("class:muted", "Press "),
+				("class:cmd_key", "ctrl-c"),
+				("class:muted", " to continue automatically.\n"),
+				("class:muted", "Press "),
+				("class:cmd_key", "enter"),
+				("class:muted", " to step.\n"),
+			]), style = lamb_engine.utils.style)
+
+
+		skip_to_end = False
+		try:
+			while (
+					(
+						(self.reduction_limit is None) or
+						(k < self.reduction_limit)
+					) and not only_macro
+				):
+
+				# Show reduction count
+				if (
+						( (k >= self.iter_update) and (k % self.iter_update == 0) )
+						and not (self.step_reduction and not skip_to_end)
+					):
+					print(f" Reducing... {k:,}", end = "\r")
+
+				# Reduce
+				red_type, node = lamb_engine.nodes.reduce(node)
+
+				# If we can't reduce this expression anymore,
+				# it's in beta-normal form.
+				if red_type == lamb_engine.nodes.ReductionType.NOTHING:
+					stop_reason = StopReason.BETA_NORMAL
+					break
+
+				# Count reductions
+				k += 1
+				if red_type == lamb_engine.nodes.ReductionType.FUNCTION_APPLY:
+					macro_expansions += 1
+
+				# Pause after step if necessary
+				if self.step_reduction and not skip_to_end:
+					try:
+						s = prompt(
+							message = FormattedText([
+								("class:prompt", lamb_engine.nodes.reduction_text[red_type]),
+								("class:prompt", f":{k:03} ")
+							] + lamb_engine.utils.lex_str(str(node))),
+							style = lamb_engine.utils.style,
+							key_bindings = step_bindings
+						)
+					except KeyboardInterrupt or EOFError:
+						skip_to_end = True
+						printf(FormattedText([
+							("class:warn", "Skipping to end."),
+						]), style = lamb_engine.utils.style)
+
+		# Gracefully catch keyboard interrupts
+		except KeyboardInterrupt:
+			stop_reason = StopReason.INTERRUPT
+
+		# Print a space between step messages
+		if self.step_reduction:
+			print("")
+
+		# Clear reduction counter if it was printed
+		if k >= self.iter_update:
+			print(" " * round(14 + math.log10(k)), end = "\r")
+
+		# Expand fully if necessary
+		if self.full_expansion:
+			o, node = lamb_engine.nodes.expand(node, force_all = True)
+			macro_expansions += o
+
+		if only_macro:
+			out_text += [
+				("class:ok", f"Displaying macro content")
+			]
+
+		else:
+			if not self.step_reduction:
+				out_text += [
+					("class:ok", f"Runtime: "),
+					("class:text", f"{time.time() - start_time:.03f} seconds"),
+					("class:text", "\n")
+				]
+
+			out_text += [
+				("class:ok", f"Exit reason: "),
+				stop_reason.value,
+				("class:text", "\n"),
+
+				("class:ok", f"Macro expansions: "),
+				("class:text", f"{macro_expansions:,}"),
+				("class:text", "\n"),
+
+				("class:ok", f"Reductions: "),
+				("class:text", f"{k:,}\t"),
+				("class:muted", f"(Limit: {self.reduction_limit:,})")
+			]
+
+		if self.full_expansion:
+			out_text += [
+				("class:text", "\n"),
+				("class:ok", "All macros have been expanded")
+			]
+
+		if (
+				stop_reason == StopReason.BETA_NORMAL or
+				stop_reason == StopReason.LOOP_DETECTED or
+				only_macro
+		):
+			out_text += [
+				("class:ok", "\n\n    => ")
+			] + lamb_engine.utils.lex_str(str(node))
+
+
+		printf(
+			FormattedText(out_text),
+			style = lamb_engine.utils.style
+		)
+
+		# Save to history
+		# Do this at the end so we don't always fully expand.
+		self.history.appendleft(
+			lamb_engine.nodes.expand( # type: ignore
+				node,
+				force_all = True
+			)[1]
+		)
+
+	def save_macro(
+			self,
+			macro: MacroDef,
+			*,
+			silent = False
+		) -> None:
+		was_rewritten = macro.label in self.macro_table
+		self.macro_table[macro.label] = macro.expr
+
+		if not silent:
+			printf(FormattedText([
+				("class:text", "Set "),
+				("class:code", macro.label),
+				("class:text", " to "),
+				("class:code", str(macro.expr))
+			]), style = lamb_engine.utils.style)
+
+	# Apply a list of definitions
+	def run(
+			self,
+			line: str,
+			*,
+			silent = False
+		) -> None:
+		e, w = self.parse(line)
+
+		# If this line is a macro definition, save the macro.
+		if isinstance(e, MacroDef):
+			self.save_macro(e, silent = silent)
+
+		# If this line is a command, do the command.
+		elif isinstance(e, Command):
+			if e.name not in cmd.commands:
+				printf(
+					FormattedText([
+						("class:warn", f"Unknown command \"{e.name}\"")
+					]),
+					style = lamb_engine.utils.style
+				)
+			else:
+				cmd.commands[e.name](e, self)
+
+		# If this line is a plain expression, reduce it.
+		elif isinstance(e, lamb_engine.nodes.Node):
+			self.reduce(e, warnings = w)
+
+		# We shouldn't ever get here.
+		else:
+			raise TypeError(f"I don't know what to do with a {type(e)}")
+
+
+	def run_lines(self, lines: list[str]):
+		for l in lines:
+			self.run(l, silent = True)

lamb_engine/utils.py

@@ -0,0 +1,165 @@
+from prompt_toolkit.styles import Style
+from prompt_toolkit.formatted_text import HTML
+from prompt_toolkit.lexers import Lexer
+from prompt_toolkit.key_binding import KeyBindings
+from prompt_toolkit import print_formatted_text as printf
+from importlib.metadata import version
+from prompt_toolkit.document import Document
+
+import re
+
+
+style = Style.from_dict({ # type: ignore
+	# Basic formatting
+	"text": "#FFFFFF",
+	"warn": "#FFA700",
+	"err": "#FF3809",
+	"prompt": "#05CFFF",
+	"ok": "#00EF7C",
+	"code": "#AAAAAA italic",
+	"muted": "#AAAAAA",
+
+	# Syntax highlighting colors
+	"syn_cmd": "#FFFFFF italic",
+	"syn_lambda": "#AAAAAA",
+	"syn_paren": "#AAAAAA",
+
+	# Command formatting
+	# cmd_h:    section titles
+	# cmd_key:  keyboard keys, usually one character
+	"cmd_h": "#FF3809 bold",
+	"cmd_key": "#00EF7C bold",
+
+	# Only used in greeting
+	"_v": "#00EF7C bold",
+	"_l": "#FF3809 bold",
+	"_s": "#00EF7C bold",
+	"_p": "#AAAAAA"
+})
+
+
+# Replace "\" with pretty "λ"s
+bindings = KeyBindings()
+@bindings.add("\\")
+def _(event):
+	event.current_buffer.insert_text("λ")
+
+# Simple lexer for highlighting.
+# Improve this later.
+class LambdaLexer(Lexer):
+	def lex_document(self, document):
+		def inner(line_no):
+			out = []
+			tmp_str = []
+			d = str(document.lines[line_no])
+
+			if d.startswith(":"):
+				return [
+					("class:syn_cmd", d)
+				]
+
+			for c in d:
+				if c in "\\λ.":
+					if len(tmp_str) != 0:
+						out.append(("class:text", "".join(tmp_str)))
+					out.append(("class:syn_lambda", c))
+					tmp_str = []
+				elif c in "()":
+					if len(tmp_str) != 0:
+						out.append(("class:text", "".join(tmp_str)))
+					out.append(("class:syn_paren", c))
+					tmp_str = []
+				else:
+					tmp_str.append(c)
+
+			if len(tmp_str) != 0:
+				out.append(("class:text", "".join(tmp_str)))
+			return out
+		return inner
+
+
+
+def lex_str(s: str) -> list[tuple[str, str]]:
+	return LambdaLexer().lex_document(Document(s))(0)
+
+def show_greeting():
+	#   |  _.._ _.|_
+	#   |_(_|| | ||_)
+	#       0.0.0
+	#
+	#       __  __
+	#    ,-`  ``  `,
+	#   (`   \      )
+	#  (`     \     `)
+	#  (,    / \    _)
+	#   (`  /   \   )
+	#    `'._.--._.'
+	#
+	# A λ calculus engine
+
+	printf(HTML("\n".join([
+		"",
+		"<_h>    |  _.._ _.|_",
+		"    |_(_|| | ||_)</_h>",
+		f"        <_v>{version('lamb_engine')}</_v>",
+		"        __  __",
+		"     ,-`  ``  `,",
+		"    (`   <_l>\\</_l>      )",
+		"   (`     <_l>\\</_l>     `)",
+		"   (,    <_l>/ \\</_l>    _)",
+		"    (`  <_l>/   \\</_l>   )",
+		"     `'._.--._.'",
+		"",
+		"<_s> A λ calculus engine</_s>",
+		"<_p> Type :help for help</_p>",
+		""
+	])), style = style)
+
+def remove_sub(s: str):
+	return re.sub("[₀₁₂₃₄₅₆₈₉]*", "", s)
+
+def base4(n: int):
+	if n == 0:
+		return [0]
+	digits = []
+	while n:
+		digits.append(n % 4)
+		n //= 4
+	return digits[::-1]
+
+def subscript(num: int):
+
+	# unicode subscripts  ₀₁₂₃ and ₄₅₆₈₉
+	# usually look different,
+	# so we'll use base 4.
+	qb = base4(num)
+
+	sub = {
+		"0": "₀",
+		"1": "₁",
+		"2": "₂",
+		"3": "₃",
+		"4": "₄",
+		"5": "₅",
+		"6": "₆",
+		"7": "₇",
+		"8": "₈",
+		"9": "₉"
+	}
+
+	sup = {
+		"0": "⁰",
+		"1": "¹",
+		"2": "²",
+		"3": "³",
+		"4": "⁴",
+		"5": "⁵",
+		"6": "⁶",
+		"7": "⁷",
+		"8": "⁸",
+		"9": "⁹"
+	}
+
+	return "".join(
+		[sub[str(x)] for x in qb]
+	)

macros.lamb

@@ -0,0 +1,77 @@
+# How to use exported files in lamb:
+#
+# [Syntax Highlighting]
+#	Most languages' syntax highlighters will
+#	highlight this code well. Set it manually
+#	in your editor.
+#
+#	Don't use a language for which you have a
+#	linter installed, you'll get lots of errors.
+#
+#	Choose a language you don't have extenstions for,
+#	and a language that uses # comments.
+#
+# The following worked well in vscode:
+# - Julia
+# - Perl
+# - Coffeescript
+# - R
+
+# [Writing macros]
+#	If you don't have a custom keyboard layout that can
+#	create λs, you may use backslashes instead.
+#	(As in `T = \ab.b`)
+#
+#	This file must only contain macro definitons. Commands will be ignored.
+#	Statements CANNOT be split among multiple lines.
+#	Comments CANNOT be on the same line as macro defintions.
+#	All leading whitespace is ignored.
+
+
+# Misc Combinators
+M = λx.(x x)
+W = (M M)
+Y = λf.( (λx.(f (x x))) (λx.(f (x x))) )
+
+
+# Booleans
+T = λab.a
+F = λab.b
+NOT = λa.(a F T)
+AND = λab.(a b F)
+OR = λab.(a T b)
+XOR = λab.((a (NOT b)) b)
+
+
+# Numbers
+# PAIR: prerequisite for H.
+#	Makes a two-value tuple, indexed with T and F.
+#
+# H: shift-and-add, prerequisite for D
+#
+# S: successor (adds 1)
+#
+# D: predecessor (subtracts 1)
+#
+# Z: tests if a number is zero
+# NZ: equivalent to `NOT Z`
+#
+# ADD: adds two numbers
+#
+# MULT: multiply two numbers
+#
+# FAC:
+#	Recursive factorial. Call with `Y FAC <number>`
+#	Don't call this with numbers bigger than 5 unless you're very patient.
+#
+#	`Y FAC 6` required 867,920 reductions and took 10 minutes to run.
+
+PAIR = λabi.(i a b)
+S = λnfa.(f (n f a))
+H = λp.((PAIR (p F)) (S (p F)))
+D = λn.(n H (PAIR 0 0) T)
+Z = λn.(n (λa.F) T)
+NZ = λn.(n (λa.T) F)
+ADD = λmn.(m S n)
+MULT = λnmf.(n (m f))
+FAC = λyn.(Z n) (1) (MULT n (y (D n)))

misc/demo.tape

@@ -0,0 +1,84 @@
+# See makedemo.sh
+
+#Output lambdemo.mp4
+Output lambdemo.gif
+
+Set FontSize 30
+Set Width 2000
+Set Height 1500
+Set FontFamily "FantasqueSansMono NF"
+Set TypingSpeed 60ms
+Set Framerate 30
+
+# Intro
+Sleep 2000ms
+Type "lamb"
+Sleep 1000ms
+Enter
+Sleep 2000ms
+
+# Demo 1: load
+Type ":load ../macros.lamb"
+Sleep 500ms
+Enter
+Sleep 2000ms
+
+Type "NOT T"
+Sleep 1000ms
+Enter
+Sleep 6s
+
+Type ":clear"
+Sleep 1000ms
+Enter
+Sleep 1500ms
+
+
+# Demo 2: stepping
+Type ":step"
+Sleep 500ms
+Enter
+Sleep 1500ms
+
+Type "NOT T"
+Sleep 100ms
+Enter
+Sleep 1500ms
+Enter
+Sleep 760ms
+Enter
+Sleep 850ms
+Enter
+Sleep 650ms
+Enter
+Sleep 700ms
+Enter
+
+Sleep 3000ms
+
+Type ":step"
+Sleep 500ms
+Enter
+Sleep 6s
+Type ":clear"
+Sleep 1000ms
+Enter
+Sleep 1500ms
+
+# Demo 3: macros
+Type "M = \x.x x"
+Sleep 500ms
+Enter
+Sleep 500ms
+
+Type "M M"
+Sleep 500ms
+Enter
+Sleep 3s
+Ctrl+c
+Sleep 1000ms
+
+Type "Y FAC 3"
+Sleep 500ms
+Enter
+Sleep 6s

misc/makedemo.sh

@@ -0,0 +1,34 @@
+#!/bin/bash
+# Should be run from the misc directory.
+# Will not work with any other root.
+
+# Create this file.
+# Should define two variables:
+# DAV_USER="name:password"
+# DAV_URL="https://site.com/dav-path"
+
+if [[ -f "secrets.sh" ]]; then
+	source secrets.sh
+else
+	echo "Cannot run without secrets.sh"
+	exit
+fi
+
+# Activate venv if not in venv
+if [[ "$VIRTUAL_ENV" == "" ]]; then
+	source ../venv/bin/activate
+fi
+
+# Make sure our venv is running the latest
+# version of lamb.
+pip install --editable ..
+
+
+# Make gif
+vhs < demo.tape
+
+# Upload
+curl \
+	--user $DAV_USER \
+	--url $DAV_URL \
+	--upload-file "lambdemo.gif"

pyproject.toml

@@ -1,30 +1,28 @@
+[build-system]
+requires = [ "setuptools>=61.0" ]
+build-backend = "setuptools.build_meta"
+
+[tool.setuptools.packages.find]
+where = [ "." ]
+include = ["lamb_engine*"]
+namespaces = false
+
+[project.scripts]
+lamb = "lamb_engine:main"
+
+
+
 [project]
-name = "Lamb"
+name = "lamb_engine"
 description = "A lambda calculus engine"
-
+version = "1.1.9"
-# We use the standard semantic versioning:
-# maj.min.pat
-#
-# Major release:
-# 1.0.0 is the first stable release.
-# Incremented on BIG breaking changes.
-#
-# Minor release:
-# Large bug fixes, new features
-#
-# Patch release:
-# Small, compatible fixes.
-version = "0.1.2"
-
 dependencies = [
 	"prompt-toolkit==3.0.31",
 	"pyparsing==3.0.9"
 ]
-
 authors = [
 	{ name="Mark", email="mark@betalupi.com" }
 ]
-
 readme = "README.md"
 requires-python = ">=3.7"
 license = {text = "GNU General Public License v3 (GPLv3)"}
@@ -35,20 +33,10 @@ classifiers = [
 	"Environment :: Console"
 ]
 
-
 [project.urls]
 "Homepage" = "https://git.betalupi.com/Mark/lamb"
 
-
+# To build:
-[build-system]
+# pip install build twine
-requires = [ "setuptools>=61.0" ]
+# python -m build
-build-backend = "setuptools.build_meta"
+# twine upload dist/lamb_engine-1.1.6* (change the version)
-
-[tool.setuptools.packages.find]
-where = ["lamb"]
-include = ["lamb*"]
-namespaces = false
-
-[project.optional-dependencies]
-# Used to build a standalone executable
-pyinstaller = [	"pyinstaller==5.5" ]