Improved printing

README.md

@@ -30,7 +30,7 @@ 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.
+Unbound variables (upper and lower case) that aren't macros will become free variables. 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.
 
@@ -76,7 +76,6 @@ Lamb treats each λ expression as a binary tree. Variable binding and reduction
 
 ## Todo (pre-release):
  - Make command output accessible in prompt
- - Prettyprint functions and rename bound variables
  - Prettier colors
  - Prevent macro-chaining recursion
  - step-by-step reduction
@@ -86,11 +85,9 @@ Lamb treats each λ expression as a binary tree. Variable binding and reduction
 
 
 ## Todo:
- - Optimization: clone only if absolutely necessary
  - Better class mutation: when is a node no longer valid?
  - Loop detection
  - Command-line options (load a file, run a set of commands)
  - $\alpha$-equivalence check
  - Unchurch macro: make church numerals human-readable
- - Smart alignment in all printouts
  - Syntax highlighting: parenthesis, bound variables, macros, etc

lamb/commands.py

@@ -62,7 +62,7 @@ def cmd_save(command, runner) -> None:
 
 	with open(target, "w") as f:
 		f.write("\n".join(
-			[f"{n} = {e}" for n, e in runner.macro_table.items()]
+			[f"{n} = {e.export()}" for n, e in runner.macro_table.items()]
 		))
 
 	printf(

lamb/node.py

@@ -1,4 +1,5 @@
 import enum
+import lamb
 
 class Direction(enum.Enum):
 	UP		= enum.auto()
@@ -207,6 +208,12 @@ class Node:
 	def __str__(self) -> str:
 		return print_node(self)
 
+	def export(self) -> str:
+		"""
+		Convert this tree to a parsable string.
+		"""
+		return print_node(self, export = True)
+
 	def bind_variables(self, *, ban_macro_name = None):
 		return bind_variables(
 			self,
@@ -214,7 +221,7 @@ class Node:
 		)
 
 class EndNode(Node):
-	def print_value(self):
+	def print_value(self, *, export: bool = False) -> str:
 		raise NotImplementedError("EndNodes MUST provide a `print_value` method!")
 
 class ExpandableEndNode(EndNode):
@@ -228,8 +235,11 @@ class FreeVar(EndNode):
 	def __repr__(self):
 		return f"<freevar {self.name}>"
 
-	def print_value(self):
-		return f"{self.name}"
+	def print_value(self, *, export: bool = False) -> str:
+		if export:
+			return f"{self.name}'"
+		else:
+			return f"{self.name}'"
 
 	def copy(self):
 		return FreeVar(self.name)
@@ -248,7 +258,7 @@ class Macro(ExpandableEndNode):
 	def __repr__(self):
 		return f"<macro {self.name}>"
 
-	def print_value(self):
+	def print_value(self, *, export: bool = False) -> str:
 		return self.name
 
 	def expand(self, *, macro_table = {}) -> tuple[ReductionType, Node]:
@@ -274,7 +284,7 @@ class Church(ExpandableEndNode):
 	def __repr__(self):
 		return f"<church {self.value}>"
 
-	def print_value(self):
+	def print_value(self, *, export: bool = False) -> str:
 		return str(self.value)
 
 	def expand(self, *, macro_table = {}) -> tuple[ReductionType, Node]:
@@ -316,7 +326,7 @@ class Bound(EndNode):
 	def __repr__(self):
 		return f"<{self.name} {self.identifier}>"
 
-	def print_value(self):
+	def print_value(self, *, export: bool = False) -> str:
 		return self.name
 
 class Func(Node):
@@ -378,15 +388,31 @@ class Call(Node):
 		return Call(None, None)  # type: ignore
 
 
-def print_node(node: Node) -> str:
+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):
-			out += n.print_value()
+			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:
@@ -502,7 +528,7 @@ def call_func(fn: Func, arg: Node):
 					raise Exception("Tried to substitute a None bound variable.")
 
 				n.parent.set_side(n.parent_side, clone(arg)) # type: ignore
-	return clone(fn.left)
+	return fn.left
 
 
 # Do a single reduction step

lamb/runner.py

@@ -116,7 +116,7 @@ class Runner:
 
 			# Show reduction count
 			if (i >= self.iter_update) and (i % self.iter_update == 0):
-				print(f" Reducing... {i}", end = "\r")
+				print(f" Reducing... {i:,}", end = "\r")
 
 			try:
 				red_type, node = lamb.node.reduce(

lamb/utils.py

@@ -71,3 +71,34 @@ def show_greeting():
 		"<_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)]
+	)

pyproject.toml

@@ -14,7 +14,7 @@ description = "A lambda calculus engine"
 #
 # Patch release:
 # Small, compatible fixes.
-version = "0.1.0"
+version = "0.1.1"
 
 dependencies = [
 	"prompt-toolkit==3.0.31",