Rewrite continues

lamb/__main__.py

@@ -46,6 +46,8 @@ r = runner.Runner(
 )
 """
 
+macro_table = {}
+
 class Direction(enum.Enum):
 	UP		= enum.auto()
 	LEFT	= enum.auto()
@@ -74,7 +76,11 @@ class Node:
 		self.left: Node | None = None
 		self.right: Node | None = None
 
-	def set_parent(self, parent, side: Direction):
+	def set_parent(self, parent, side):
+		if (parent is not None) and (side is None):
+			raise Exception("If a node has a parent, it must have a direction.")
+		if (parent is None) and (side is not None):
+			raise Exception("If a node has no parent, it cannot have a direction.")
 		self.parent = parent
 		self.parent_side = side
 
@@ -89,15 +95,33 @@ class Node:
 		return Direction.UP, self.right
 
 	def go_up(self):
-		if self.parent is None:
-			raise Exception("Can't go up when parent is None")
 		return self.parent_side, self.parent
 
-class EndNode:
+	def clone(self):
-	def print_value(self):
+		raise NotImplementedError("Nodes MUST provide a `clone` method!")
-		raise NotImplementedError("EndNodes MUST have a print_value method!")
 
-class Macro(Node, EndNode):
+class EndNode(Node):
+	def print_value(self):
+		raise NotImplementedError("EndNodes MUST provide a `print_value` method!")
+
+class ExpandableEndNode(EndNode):
+	def expand(self):
+		raise NotImplementedError("ExpandableEndNodes MUST provide an `expand` method!")
+
+class FreeVar(EndNode):
+	def __init__(self, name: str):
+		self.name = name
+
+	def __repr__(self):
+		return f"<freevar {self.name}>"
+
+	def print_value(self):
+		return f"{self.name}"
+
+	def clone(self):
+		return FreeVar(self.name)
+
+class Macro(ExpandableEndNode):
 	@staticmethod
 	def from_parse(results):
 		return Macro(results[0])
@@ -114,10 +138,21 @@ class Macro(Node, EndNode):
 	def print_value(self):
 		return self.name
 
-class Church(Node, EndNode):
+	def expand(self):
+		if self.name in macro_table:
+			return macro_table[self.name]
+		else:
+			f = FreeVar(self.name)
+			f.set_parent(self.parent, self.parent_side) # type: ignore
+			return f
+
+	def clone(self):
+		return Macro(self.name)
+
+class Church(ExpandableEndNode):
 	@staticmethod
 	def from_parse(results):
-		return Church(results[0])
+		return Church(int(results[0]))
 
 	def __init__(self, value: int) -> None:
 		super().__init__()
@@ -131,10 +166,7 @@ class Church(Node, EndNode):
 	def print_value(self):
 		return str(self.value)
 
-	def to_church(self):
+	def expand(self):
-		"""
-		Return this number as an expanded church numeral.
-		"""
 		f = Bound("f")
 		a = Bound("a")
 		chain = a
@@ -147,9 +179,11 @@ class Church(Node, EndNode):
 			Func(a, chain)
 		)
 
+	def clone(self):
+		return Church(self.value)
 
 bound_counter = 0
-class Bound(Node, EndNode):
+class Bound(EndNode):
 	def __init__(self, name: str, *, forced_id = None):
 		self.name = name
 		global bound_counter
@@ -161,13 +195,7 @@ class Bound(Node, EndNode):
 			self.identifier = forced_id
 
 	def clone(self):
-		"""
+		return Bound(self.name, forced_id = self.identifier)
-		Return a new bound variable equivalent to this one.
-		"""
-		return Bound(
-			self.name,
-			forced_id = self.identifier
-		)
 
 	def __eq__(self, other):
 		if not isinstance(other, Bound):
@@ -207,6 +235,9 @@ class Func(Node):
 	def __repr__(self):
 		return f"<func {self.input!r} {self.left!r}>"
 
+	def clone(self):
+		return Func(self.input, None) # type: ignore
+
 class Call(Node):
 	@staticmethod
 	def from_parse(results):
@@ -237,6 +268,9 @@ class Call(Node):
 	def __repr__(self):
 		return f"<call {self.left!r} {self.right!r}>"
 
+	def clone(self):
+		return Call(None, None)  # type: ignore
+
 class MacroDef:
 	@staticmethod
 	def from_parse(result):
@@ -278,21 +312,79 @@ p = lamb.parser.LambdaParser(
 )
 
 
-def print_expr(expr) -> str:
 
-	if isinstance(expr, MacroDef):
+def clone_one(ptr, out):
-		return f"{expr.label} = {print_expr(expr.expr)}"
+	if ptr.parent_side == Direction.LEFT:
+		out.left = ptr.clone()
+		out.left.set_parent(out, Direction.LEFT)
+	else:
+		out.right = ptr.clone()
+		out.right.set_parent(out, Direction.RIGHT)
 
-	elif isinstance(expr, Node):
+def clone(expr: Node):
+	if not isinstance(expr, Node):
+		raise TypeError(f"I don't know what to do with a {type(expr)}")
+
+	# Disconnect parent while cloning
+	old_parent = expr.parent
+	expr.parent = None
+
+	out = expr.clone()
+	out_ptr = out # Stays one step behind ptr, in the new tree.
 	ptr = expr
 	from_side = Direction.UP
 
-		out = ""
+	if isinstance(expr, EndNode):
+		return out
 
 	while True:
+		if isinstance(ptr, EndNode):
+			from_side, ptr = ptr.go_up()
+			_, out_ptr = out_ptr.go_up()
+		elif isinstance(ptr, Func):
+			if from_side == Direction.UP:
+				from_side, ptr = ptr.go_left()
+				clone_one(ptr, out_ptr)
+				_, 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()
+				clone_one(ptr, out_ptr)
+				_, out_ptr = out_ptr.go_left()
+			elif from_side == Direction.LEFT:
+				from_side, ptr = ptr.go_right()
+				clone_one(ptr, out_ptr)
+				_, 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 None:
+			break
+
+	expr.parent = old_parent
+	return out
+
+def print_expr(expr) -> str:
+
+	out = ""
+
+	# Type check
+	if isinstance(expr, MacroDef):
+		out = expr.label + " = "
+		expr = expr.expr
+	elif not isinstance(expr, Node):
+		raise TypeError(f"I don't know what to do with a {type(expr)}")
+
+	ptr = expr
+	from_side = Direction.UP
+
+	while True:
+		print(ptr)
 		if isinstance(ptr, EndNode):
 			out += ptr.print_value()
-				if ptr.parent is not None:
 			from_side, ptr = ptr.go_up()
 
 		elif isinstance(ptr, Func):
@@ -305,7 +397,6 @@ def print_expr(expr) -> str:
 					out += "."
 				from_side, ptr = ptr.go_left()
 			elif from_side == Direction.LEFT:
-					if ptr.parent is not None:
 				from_side, ptr = ptr.go_up()
 
 		elif isinstance(ptr, Call):
@@ -317,25 +408,22 @@ def print_expr(expr) -> str:
 				from_side, ptr = ptr.go_right()
 			elif from_side == Direction.RIGHT:
 				out += ")"
-					if ptr.parent is not None:
 				from_side, ptr = ptr.go_up()
 
-			if ptr.parent is None:
+		if ptr is None:
 			break
 	return out
 
-	else:
-		raise TypeError(f"I don't know what to do with a {type(expr)}")
-
 def bind_variables(expr) -> None:
 
+	# Type check
 	if isinstance(expr, MacroDef):
-		bind_variables(expr.expr)
+		expr = expr.expr
+	elif not isinstance(expr, Node):
+		raise TypeError(f"I don't know what to do with a {type(expr)}")
 
-	elif isinstance(expr, Node):
 	ptr = expr
 	from_side = Direction.UP
-
 	bound_variables = {}
 
 	while True:
@@ -358,14 +446,12 @@ def bind_variables(expr) -> None:
 				# If we can't move down the tree, move up.
 				if isinstance(ptr.left, EndNode):
 					del bound_variables[ptr.input.name]
-						if ptr.parent is not None:
 					from_side, ptr = ptr.go_up()
 				else:
 					from_side, ptr = ptr.go_left()
 
 			elif from_side == Direction.LEFT:
 				del bound_variables[ptr.input.name]
-					if ptr.parent is not None:
 				from_side, ptr = ptr.go_up()
 
 		elif isinstance(ptr, Call):
@@ -384,31 +470,127 @@ def bind_variables(expr) -> None:
 					from_side, ptr = ptr.go_left()
 				elif not isinstance(ptr.right, EndNode):
 					from_side, ptr = ptr.go_right()
-					elif ptr.parent is not None:
+				else:
 					from_side, ptr = ptr.go_up()
 
 			elif from_side == Direction.LEFT:
-					if isinstance(ptr.right, Macro):
-						if ptr.right.name in bound_variables:
-							ptr.right = bound_variables[ptr.right.name].clone()
-							ptr.right.set_parent(ptr, Direction.RIGHT)
-
 				if not isinstance(ptr.right, EndNode):
 					from_side, ptr = ptr.go_right()
-					elif ptr.parent is not None:
+				else:
 					from_side, ptr = ptr.go_up()
 
 			elif from_side == Direction.RIGHT:
-					if ptr.parent is not None:
 				from_side, ptr = ptr.go_up()
 
-			if ptr.parent is None:
+		if ptr is None:
 			break
 
+
+# Apply a function.
+# Returns the function's output.
+def call_func(fn: Func, arg: Node):
+	ptr = fn
+
+	# Temporarily disconnect this function's
+	# parent to keep our pointer inside this
+	# subtree.
+	old_parent = fn.parent
+	fn.parent = None
+
+	from_side = Direction.UP
+
+	while True:
+		if isinstance(ptr, Bound):
+			if ptr == fn.input:
+				if ptr.parent is None:
+					raise Exception("Tried to substitute a None bound variable.")
+
+				if ptr.parent_side == Direction.LEFT:
+					ptr.parent.left = clone(arg)
+					ptr.parent.left.set_parent(ptr, Direction.LEFT)
 				else:
-		raise TypeError(f"I don't know what to do with a {type(expr)}")
+					ptr.parent.right = clone(arg)
+					ptr.parent.right.set_parent(ptr, Direction.RIGHT)
+
+			from_side, ptr = ptr.go_up()
+
+		elif isinstance(ptr, Func):
+			if from_side == Direction.UP:
+				from_side, ptr = ptr.go_left()
+			elif from_side == Direction.LEFT:
+				from_side, ptr = ptr.go_up()
+
+		elif isinstance(ptr, Call):
+			if from_side == Direction.UP:
+				from_side, ptr = ptr.go_left()
+			elif from_side == Direction.LEFT:
+				from_side, ptr = ptr.go_right()
+			elif from_side == Direction.RIGHT:
+				from_side, ptr = ptr.go_up()
+		else:
+			from_side, ptr = ptr.go_up()
+
+		if ptr is None:
+			break
+
+	fn.parent = old_parent
+	return fn.left
+
+
+# Do a single reduction step
+def reduce(expr) -> tuple[bool, Node]:
+
+	if not isinstance(expr, Node):
+		raise TypeError(f"I can't reduce a {type(expr)}")
+
+	ptr = expr
+	from_side = Direction.UP
+	reduced = False
+
+	while True:
+		print("redu", ptr)
+
+		if isinstance(ptr, Call):
+			if from_side == Direction.UP:
+				if isinstance(ptr.left, Func):
+					if ptr.parent is None:
+						expr = call_func(ptr.left, ptr.right)
+						expr.set_parent(None, None)
+					else:
+						ptr.parent.left = call_func(ptr.left, ptr.right)
+						ptr.parent.left.set_parent(ptr.parent, Direction.LEFT)
+					reduced = True
+					break
+				elif isinstance(ptr.left, ExpandableEndNode):
+					ptr.left = ptr.left.expand()
+					reduced = True
+					break
+				elif isinstance(ptr.left, Call):
+					from_side, ptr = ptr.go_left()
+				else:
+					from_side, ptr = ptr.go_right()
+
+			else:
+				from_side, ptr = ptr.go_up()
+
+		elif isinstance(ptr, Func):
+			if from_side == Direction.UP:
+				from_side, ptr = ptr.go_left()
+			else:
+				from_side, ptr = ptr.go_up()
+
+		elif isinstance(ptr, EndNode):
+			from_side, ptr = ptr.go_up()
+
+		if ptr is None:
+			break
+
+	return reduced, expr
+
 
 for l in [
+	"T = λab.a",
+	"F = λab.b",
 	"NOT = λa.(a F T)",
 	"AND = λab.(a F b)",
 	"OR = λab.(a T b)",
@@ -420,8 +602,21 @@ for l in [
 	"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)))"
+	"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)))",
+	"S (λfa.f a)"
 ]:
 	n = p.parse_line(l)
 	bind_variables(n)
+
+	if isinstance(n, MacroDef):
+		macro_table[n.label] = n.expr
 		print(print_expr(n))
+	else:
+		for i in range(10):
+			r, n = reduce(n)
+			if not r:
+				break
+		print(print_expr(n))
+		#print(print_expr(clone(n)))

lamb/parser.py

@@ -47,7 +47,7 @@ class LambdaParser:
 		)
 
 		self.pp_expr <<= (
-			#self.pp_church ^
+			self.pp_church ^
 			self.pp_lambda_fun ^
 			self.pp_name ^
 			(self.lp + self.pp_expr + self.rp) ^

lamb/tokens.py

@@ -1,239 +0,0 @@
-import enum
-import lamb.utils as utils
-
-
-
-class ReductionType(enum.Enum):
-	MACRO_EXPAND	= enum.auto()
-	MACRO_TO_FREE	= enum.auto()
-	FUNCTION_APPLY	= enum.auto()
-	AUTOCHURCH		= enum.auto()
-
-
-class ReductionStatus:
-	"""
-	This object helps organize reduction output.
-	An instance is returned after every reduction step.
-	"""
-
-	def __init__(
-		self,
-		*,
-		output,
-		was_reduced: bool,
-		reduction_type: ReductionType | None = None
-	):
-		# The new expression
-		self.output = output
-
-		# What did we do?
-		# Will be None if was_reduced is false.
-		self.reduction_type = reduction_type
-
-		# Did this reduction change anything?
-		# If we try to reduce an irreducible expression,
-		# this will be false.
-		self.was_reduced = was_reduced
-
-
-class church_num(LambdaToken):
-	def reduce(self, *, force_substitute = False) -> ReductionStatus:
-		if force_substitute: # Only expand macros if we NEED to
-			return ReductionStatus(
-				output = self.to_church(),
-				was_reduced = True,
-				reduction_type = ReductionType.AUTOCHURCH
-			)
-		else: # Otherwise, do nothing.
-			return ReductionStatus(
-				output = self,
-				was_reduced = False
-			)
-
-
-class free_variable(LambdaToken):
-	"""
-	Represents a free variable.
-
-	This object does not reduce to
-	anything, since it has no meaning.
-
-	Any name in an expression that isn't
-	a macro or a bound variable is assumed
-	to be a free variable.
-	"""
-
-	def __init__(self, label: str):
-		self.label = label
-
-	def __repr__(self):
-		return f"<freevar {self.label}>"
-
-	def __str__(self):
-		return f"{self.label}"
-
-class macro(LambdaToken):
-	def reduce(
-			self,
-			*,
-			# To keep output readable, we avoid expanding macros as often as possible.
-			# Macros are irreducible if force_substitute is false.
-			force_substitute = False,
-
-			# If this is false, error when macros aren't defined instead of
-			# invisibly making a free variable.
-			auto_free_vars = True
-		) -> ReductionStatus:
-
-		if (self.name in self.runner.macro_table) and force_substitute:
-			if force_substitute: # Only expand macros if we NEED to
-				return ReductionStatus(
-					output = self.runner.macro_table[self.name],
-					reduction_type = ReductionType.MACRO_EXPAND,
-					was_reduced = True
-				)
-			else: # Otherwise, do nothing.
-				return ReductionStatus(
-					output = self,
-					was_reduced = False
-				)
-
-		elif not auto_free_vars:
-			raise ReductionError(f"Macro {self.name} is not defined")
-
-		else:
-			return ReductionStatus(
-				output = free_variable(self.name),
-				reduction_type = ReductionType.MACRO_TO_FREE,
-				was_reduced = True
-			)
-
-
-class lambda_func(LambdaToken):
-	def reduce(self) -> ReductionStatus:
-
-		r = self.output.reduce()
-
-		return ReductionStatus(
-			was_reduced = r.was_reduced,
-			reduction_type = r.reduction_type,
-			output = lambda_func(
-				self.input,
-				r.output
-			)
-		)
-
-
-	def apply(
-			self,
-			val,
-			*,
-			bound_var: bound_variable | None = None
-		):
-		"""
-		Substitute `bound_var` into all instances of a bound variable `var`.
-		If `bound_var` is none, use this functions bound variable.
-		Returns a new object.
-		"""
-
-		calling_self = False
-		if bound_var is None:
-			calling_self = True
-			bound_var = self.input # type: ignore
-		new_out = self.output
-		if isinstance(self.output, bound_variable):
-			if self.output == bound_var:
-				new_out = val
-		elif isinstance(self.output, lambda_func):
-			new_out = self.output.apply(val, bound_var = bound_var)
-		elif isinstance(self.output, lambda_apply):
-			new_out = self.output.sub_bound_var(val, bound_var = bound_var) # type: ignore
-
-		# If we're applying THIS function,
-		# just give the output
-		if calling_self:
-			return new_out
-
-		# If we're applying another function,
-		# return this one with substitutions
-		else:
-			return lambda_func(
-				self.input,
-				new_out
-			)
-
-
-class lambda_apply(LambdaToken):
-	def sub_bound_var(
-		self,
-		val,
-		*,
-		bound_var: bound_variable
-	):
-
-		new_fn = self.fn
-		if isinstance(self.fn, bound_variable):
-			if self.fn == bound_var:
-				new_fn = val
-		elif isinstance(self.fn, lambda_func):
-			new_fn = self.fn.apply(val, bound_var = bound_var)
-		elif isinstance(self.fn, lambda_apply):
-			new_fn = self.fn.sub_bound_var(val, bound_var = bound_var)
-
-		new_arg = self.arg
-		if isinstance(self.arg, bound_variable):
-			if self.arg == bound_var:
-				new_arg = val
-		elif isinstance(self.arg, lambda_func):
-			new_arg = self.arg.apply(val, bound_var = bound_var)
-		elif isinstance(self.arg, lambda_apply):
-			new_arg = self.arg.sub_bound_var(val, bound_var = bound_var)
-
-		return lambda_apply(
-			new_fn,
-			new_arg
-		)
-
-	def reduce(self) -> ReductionStatus:
-
-		# If we can directly apply self.fn, do so.
-		if isinstance(self.fn, lambda_func):
-			return ReductionStatus(
-				was_reduced = True,
-				reduction_type = ReductionType.FUNCTION_APPLY,
-				output = self.fn.apply(self.arg)
-			)
-
-		# Otherwise, try to reduce self.fn.
-		# If that is impossible, try to reduce self.arg.
-		else:
-			if isinstance(self.fn, macro) or isinstance(self.fn, church_num):
-				# Macros must be reduced before we apply them as functions.
-				# This is the only place we force substitution.
-				r = self.fn.reduce(
-					force_substitute = True
-				)
-			else:
-				r = self.fn.reduce()
-
-			if r.was_reduced:
-				return ReductionStatus(
-					was_reduced = True,
-					reduction_type = r.reduction_type,
-					output = lambda_apply(
-						r.output,
-						self.arg
-					)
-				)
-
-			else:
-				r = self.arg.reduce()
-
-				return ReductionStatus(
-					was_reduced = r.was_reduced,
-					reduction_type = r.reduction_type,
-					output = lambda_apply(
-						self.fn,
-						r.output
-					)
-				)