Added variable binding
parent
c5df3fcbed
commit
455e447999
GPG Key ID:
AD62BB059C2AAEE4
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@ -3,7 +3,7 @@
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## Todo (pre-release):
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- $\alpha$-equivalence check
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- Prettyprint functions (combine args, rename bound variables)
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- Prettyprint functions (rename bound variables)
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- Write a nice README
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- Handle or avoid recursion errors
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- Fix colors
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367
lamb/__main__.py
367
lamb/__main__.py
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@ -7,10 +7,9 @@ from prompt_toolkit.key_binding import KeyBindings
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from prompt_toolkit.lexers import Lexer
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from pyparsing import exceptions as ppx
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import enum
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import lamb.parser
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import lamb.runner as runner
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import lamb.tokens as tokens
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import lamb.utils as utils
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@ -47,44 +46,58 @@ r = runner.Runner(
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)
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"""
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class Direction(enum.Enum):
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UP = enum.auto()
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LEFT = enum.auto()
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RIGHT = enum.auto()
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class ReductionError(Exception):
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"""
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Raised when we encounter an error while reducing.
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These should be caught and elegantly presented to the user.
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"""
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def __init__(self, msg: str):
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self.msg = msg
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class Node:
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def __init__(self):
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# The node this one is connected to.
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# None if this is the top node.
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self.parent: Node | None = None
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# True if we're connected to the left side
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# of the parent, False otherwise.
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self.parent_left: bool | None = None
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# What direction this is relative to the parent.
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# Left of Right.
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self.parent_side: Direction | None = None
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# Left and right nodes, None if empty
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self.left: Node | None = None
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self.right: Node | None = None
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def set_parent(self, parent, is_left):
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def set_parent(self, parent, side: Direction):
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self.parent = parent
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self.parent_left = is_left
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self.parent_side = side
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def go_left(self):
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if self.left is None:
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raise Exception("Can't go left when left is None")
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return None, self.left
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return Direction.UP, self.left
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def go_right(self):
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if self.right is None:
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raise Exception("Can't go right when right is None")
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return None, self.right
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return Direction.UP, self.right
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def go_up(self):
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if self.parent is None:
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raise Exception("Can't go up when parent is None")
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return self.parent_left, self.parent
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return self.parent_side, self.parent
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def to_node(result_pair) -> Node:
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return result_pair[0].from_parse(result_pair[1])
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class EndNode:
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def print_value(self):
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raise NotImplementedError("EndNodes MUST have a print_value method!")
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class Macro(Node):
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class Macro(Node, EndNode):
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@staticmethod
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def from_parse(results):
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return Macro(results[0])
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@ -98,29 +111,98 @@ class Macro(Node):
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def __repr__(self):
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return f"<macro {self.name}>"
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def print_value(self):
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return self.name
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class Church(Node, EndNode):
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@staticmethod
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def from_parse(results):
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return Church(results[0])
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def __init__(self, value: int) -> None:
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super().__init__()
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self.value = value
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self.left = None
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self.right = None
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def __repr__(self):
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return f"<church {self.value}>"
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def print_value(self):
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return str(self.value)
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def to_church(self):
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"""
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Return this number as an expanded church numeral.
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"""
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f = Bound("f")
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a = Bound("a")
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chain = a
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for i in range(self.value):
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chain = Call(f, chain)
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return Func(
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f,
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Func(a, chain)
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)
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bound_counter = 0
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class Bound(Node, EndNode):
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def __init__(self, name: str, *, forced_id = None):
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self.name = name
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global bound_counter
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if forced_id is None:
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self.identifier = bound_counter
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bound_counter += 1
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else:
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self.identifier = forced_id
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def clone(self):
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"""
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Return a new bound variable equivalent to this one.
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"""
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return Bound(
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self.name,
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forced_id = self.identifier
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)
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def __eq__(self, other):
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if not isinstance(other, Bound):
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raise TypeError(f"Cannot compare bound_variable with {type(other)}")
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return self.identifier == other.identifier
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def __repr__(self):
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return f"<{self.name} {self.identifier}>"
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def print_value(self):
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return self.name
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class Func(Node):
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@staticmethod
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def from_parse(result):
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if len(result[0]) == 1:
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i = to_node(result[0][0])
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below = to_node(result[1])
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i = result[0][0]
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below = result[1]
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this = Func(i, below) # type: ignore
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below.set_parent(this, True)
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below.set_parent(this, Direction.LEFT)
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return this
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else:
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i = to_node(result[0].pop(0))
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i = result[0].pop(0)
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below = Func.from_parse(result)
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this = Func(i, below) # type: ignore
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below.set_parent(this, True)
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below.set_parent(this, Direction.LEFT)
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return this
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def __init__(self, input: Macro, output: Node) -> None:
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def __init__(self, input: Macro | Bound, output: Node) -> None:
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super().__init__()
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self.input = input
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self.left = output
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self.right = None
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self.input: Macro | Bound = input
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self.left: Node = output
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self.right: None = None
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def __repr__(self):
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return f"<func {self.input!r} {self.left!r}>"
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@ -130,93 +212,203 @@ class Call(Node):
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def from_parse(results):
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if len(results) == 2:
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left = results[0]
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if not isinstance(left, Node):
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left = to_node(left)
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right = to_node(results[1])
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right = results[1]
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this = Call(left, right)
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left.set_parent(this, True)
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right.set_parent(this, False)
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left.set_parent(this, Direction.LEFT)
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right.set_parent(this, Direction.RIGHT)
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return this
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else:
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left = results[0]
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if not isinstance(left, Node):
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left = to_node(left)
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right = to_node(results[1])
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right = results[1]
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this = Call(left, right)
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left.set_parent(this, True)
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right.set_parent(this, False)
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left.set_parent(this, Direction.LEFT)
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right.set_parent(this, Direction.RIGHT)
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return Call.from_parse(
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[this] + results[2:]
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)
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def __init__(self, fn: Node, arg: Node) -> None:
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super().__init__()
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self.left = fn
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self.right = arg
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self.left: Node = fn
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self.right: Node = arg
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def __repr__(self):
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return f"<call {self.left!r} {self.right!r}>"
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class MacroDef:
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@staticmethod
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def from_parse(result):
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return MacroDef(
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result[0].name,
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result[1]
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)
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def __init__(self, label: str, expr: Node):
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self.label = label
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self.expr = expr
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def __repr__(self):
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return f"<{self.label} := {self.expr!r}>"
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def __str__(self):
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return f"{self.label} := {self.expr}"
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class Command:
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@staticmethod
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def from_parse(result):
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return Command(
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result[0],
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result[1:]
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)
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def __init__(self, name, args):
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self.name = name
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self.args = args
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p = lamb.parser.LambdaParser(
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action_func = lambda x: (Func, x),
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action_bound = lambda x: (Macro, x),
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action_macro = lambda x: (Macro, x),
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action_call = lambda x: (Call, x)
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action_func = Func.from_parse,
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action_bound = Macro.from_parse,
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action_macro = Macro.from_parse,
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action_call = Call.from_parse,
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action_church = Church.from_parse,
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action_macro_def = MacroDef.from_parse,
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action_command = Command.from_parse
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)
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def traverse(node: Node):
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ptr = node
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back_from_left = None
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def print_expr(expr) -> str:
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out = ""
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if isinstance(expr, MacroDef):
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return f"{expr.label} = {print_expr(expr.expr)}"
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while True:
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if isinstance(ptr, Macro):
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out += ptr.name
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back_from_left, ptr = ptr.go_up()
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if isinstance(ptr, Func):
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if back_from_left is None:
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if isinstance(ptr.parent, Func):
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out += ptr.input.name
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else:
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out += "λ" + ptr.input.name
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if not isinstance(ptr.left, Func):
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out += "."
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back_from_left, ptr = ptr.go_left()
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elif back_from_left is True:
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back_from_left, ptr = ptr.go_up()
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if isinstance(ptr, Call):
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if back_from_left is None:
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out += "("
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back_from_left, ptr = ptr.go_left()
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elif back_from_left is True:
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out += " "
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back_from_left, ptr = ptr.go_right()
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elif back_from_left is False:
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out += ")"
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back_from_left, ptr = ptr.go_up()
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elif isinstance(expr, Node):
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ptr = expr
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from_side = Direction.UP
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if ptr.parent is None:
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break
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return out
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out = ""
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while True:
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if isinstance(ptr, EndNode):
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out += ptr.print_value()
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if ptr.parent is not None:
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from_side, ptr = ptr.go_up()
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elif isinstance(ptr, Func):
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if from_side == Direction.UP:
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if isinstance(ptr.parent, Func):
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out += ptr.input.name
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else:
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out += "λ" + ptr.input.name
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if not isinstance(ptr.left, Func):
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out += "."
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from_side, ptr = ptr.go_left()
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elif from_side == Direction.LEFT:
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if ptr.parent is not None:
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from_side, ptr = ptr.go_up()
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elif isinstance(ptr, Call):
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if from_side == Direction.UP:
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out += "("
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from_side, ptr = ptr.go_left()
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elif from_side == Direction.LEFT:
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out += " "
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from_side, ptr = ptr.go_right()
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elif from_side == Direction.RIGHT:
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out += ")"
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if ptr.parent is not None:
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from_side, ptr = ptr.go_up()
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if ptr.parent is None:
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break
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return out
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else:
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raise TypeError(f"I don't know what to do with a {type(expr)}")
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def bind_variables(expr) -> None:
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if isinstance(expr, MacroDef):
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bind_variables(expr.expr)
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elif isinstance(expr, Node):
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ptr = expr
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from_side = Direction.UP
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bound_variables = {}
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while True:
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if isinstance(ptr, Func):
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if from_side == Direction.UP:
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# Add this function's input to the table of bound variables.
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# If it is already there, raise an error.
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if (ptr.input.name in bound_variables):
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raise ReductionError(f"Bound variable name conflict: \"{ptr.input.name}\"")
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else:
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bound_variables[ptr.input.name] = Bound(ptr.input.name)
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ptr.input = bound_variables[ptr.input.name]
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# If output is a macro, swap it with a bound variable.
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if isinstance(ptr.left, Macro):
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if ptr.left.name in bound_variables:
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ptr.left = bound_variables[ptr.left.name].clone()
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ptr.left.set_parent(ptr, Direction.LEFT)
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# If we can't move down the tree, move up.
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if isinstance(ptr.left, EndNode):
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del bound_variables[ptr.input.name]
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if ptr.parent is not None:
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from_side, ptr = ptr.go_up()
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else:
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from_side, ptr = ptr.go_left()
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elif from_side == Direction.LEFT:
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del bound_variables[ptr.input.name]
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if ptr.parent is not None:
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from_side, ptr = ptr.go_up()
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elif isinstance(ptr, Call):
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if from_side == Direction.UP:
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# Bind macros
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if isinstance(ptr.left, Macro):
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if ptr.left.name in bound_variables:
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ptr.left = bound_variables[ptr.left.name].clone()
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ptr.left.set_parent(ptr, Direction.LEFT)
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if isinstance(ptr.right, Macro):
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if ptr.right.name in bound_variables:
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ptr.right = bound_variables[ptr.right.name].clone()
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ptr.right.set_parent(ptr, Direction.RIGHT)
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if not isinstance(ptr.left, EndNode):
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from_side, ptr = ptr.go_left()
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elif not isinstance(ptr.right, EndNode):
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from_side, ptr = ptr.go_right()
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elif ptr.parent is not None:
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from_side, ptr = ptr.go_up()
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elif from_side == Direction.LEFT:
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if isinstance(ptr.right, Macro):
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if ptr.right.name in bound_variables:
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ptr.right = bound_variables[ptr.right.name].clone()
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ptr.right.set_parent(ptr, Direction.RIGHT)
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if not isinstance(ptr.right, EndNode):
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from_side, ptr = ptr.go_right()
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elif ptr.parent is not None:
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from_side, ptr = ptr.go_up()
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elif from_side == Direction.RIGHT:
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if ptr.parent is not None:
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from_side, ptr = ptr.go_up()
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if ptr.parent is None:
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break
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else:
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raise TypeError(f"I don't know what to do with a {type(expr)}")
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for l in [
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"λab.(a (NOT a b) b)",
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"λnmf.n (m f)",
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"λf.(λx. f(x x))(λx.f(x x))",
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]:
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i = p.parse_line(l)
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#print(i)
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n = to_node(i)
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#print(n)
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print(traverse(n))
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"""
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"NOT = λa.(a F T)",
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"AND = λab.(a F b)",
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"OR = λab.(a T b)",
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@ -228,5 +420,8 @@ for l in [
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"S = λnfa.(f (n f a))",
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"Z = λn.n (λa.F) T",
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"MULT = λnmf.n (m f)",
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"H = λp.((PAIR (p F)) (S (p F)))",
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])"""
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"H = λp.((PAIR (p F)) (S (p F)))"
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]:
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n = p.parse_line(l)
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bind_variables(n)
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print(print_expr(n))
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@ -67,9 +67,9 @@ class LambdaParser:
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def __init__(
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self,
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*,
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#action_command,
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#action_macro_def,
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#action_church,
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action_command,
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action_macro_def,
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action_church,
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action_func,
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action_bound,
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action_macro,
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@ -78,9 +78,9 @@ class LambdaParser:
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self.make_parser()
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#self.pp_command.set_parse_action(action_command)
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#self.pp_macro_def.set_parse_action(action_macro_def)
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#self.pp_church.set_parse_action(action_church)
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self.pp_command.set_parse_action(action_command)
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self.pp_macro_def.set_parse_action(action_macro_def)
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self.pp_church.set_parse_action(action_church)
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self.pp_lambda_fun.set_parse_action(action_func)
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self.pp_macro.set_parse_action(action_macro)
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self.pp_bound.set_parse_action(action_bound)
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360
lamb/tokens.py
360
lamb/tokens.py
|
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@ -1,14 +1,7 @@
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import enum
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import lamb.utils as utils
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|
||||
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 ReductionType(enum.Enum):
|
||||
MACRO_EXPAND = enum.auto()
|
||||
|
|
@ -42,56 +35,8 @@ class ReductionStatus:
|
|||
# this will be false.
|
||||
self.was_reduced = was_reduced
|
||||
|
||||
class LambdaToken:
|
||||
"""
|
||||
Base class for all lambda tokens.
|
||||
"""
|
||||
|
||||
def set_runner(self, runner):
|
||||
self.runner = runner
|
||||
|
||||
def bind_variables(self, *, ban_macro_name: str | None = None) -> None:
|
||||
pass
|
||||
|
||||
def reduce(self) -> ReductionStatus:
|
||||
return ReductionStatus(
|
||||
was_reduced = False,
|
||||
output = self
|
||||
)
|
||||
|
||||
class church_num(LambdaToken):
|
||||
"""
|
||||
Represents a Church numeral.
|
||||
"""
|
||||
@staticmethod
|
||||
def from_parse(result):
|
||||
return church_num(
|
||||
int(result[0]),
|
||||
)
|
||||
|
||||
def __init__(self, val):
|
||||
self.val = val
|
||||
def __repr__(self):
|
||||
return f"<{self.val}>"
|
||||
def __str__(self):
|
||||
return f"{self.val}"
|
||||
|
||||
def to_church(self):
|
||||
"""
|
||||
Return this number as an expanded church numeral.
|
||||
"""
|
||||
f = bound_variable("f", runner = self.runner)
|
||||
a = bound_variable("a", runner = self.runner)
|
||||
chain = a
|
||||
|
||||
for i in range(self.val):
|
||||
chain = lambda_apply(f, chain)
|
||||
|
||||
return lambda_func(
|
||||
f,
|
||||
lambda_func(a, chain)
|
||||
)
|
||||
|
||||
def reduce(self, *, force_substitute = False) -> ReductionStatus:
|
||||
if force_substitute: # Only expand macros if we NEED to
|
||||
return ReductionStatus(
|
||||
|
|
@ -127,53 +72,7 @@ class free_variable(LambdaToken):
|
|||
def __str__(self):
|
||||
return f"{self.label}"
|
||||
|
||||
class command(LambdaToken):
|
||||
@staticmethod
|
||||
def from_parse(result):
|
||||
return command(
|
||||
result[0],
|
||||
result[1:]
|
||||
)
|
||||
|
||||
def __init__(self, name, args):
|
||||
self.name = name
|
||||
self.args = args
|
||||
|
||||
class macro(LambdaToken):
|
||||
"""
|
||||
Represents a "macro" in lambda calculus,
|
||||
a variable that reduces to an expression.
|
||||
|
||||
These don't have any inherent logic, they
|
||||
just make writing and reading expressions
|
||||
easier.
|
||||
|
||||
These are defined as follows:
|
||||
<macro name> = <expression>
|
||||
"""
|
||||
|
||||
@staticmethod
|
||||
def from_parse(result):
|
||||
return macro(
|
||||
result[0],
|
||||
)
|
||||
|
||||
def __init__(self, name):
|
||||
self.name = name
|
||||
def __repr__(self):
|
||||
return f"<{self.name}>"
|
||||
def __str__(self):
|
||||
return self.name
|
||||
|
||||
def __eq__(self, other):
|
||||
if not isinstance(other, macro):
|
||||
raise TypeError("Can only compare macro with macro")
|
||||
return self.name == other.name
|
||||
|
||||
def bind_variables(self, *, ban_macro_name=None) -> None:
|
||||
if self.name == ban_macro_name:
|
||||
raise ReductionError(f"Cannot use macro \"{ban_macro_name}\" here.")
|
||||
|
||||
def reduce(
|
||||
self,
|
||||
*,
|
||||
|
|
@ -209,185 +108,8 @@ class macro(LambdaToken):
|
|||
was_reduced = True
|
||||
)
|
||||
|
||||
class macro_expression(LambdaToken):
|
||||
"""
|
||||
Represents a line that looks like
|
||||
<name> = <expression>
|
||||
|
||||
Doesn't do anything particularly interesting,
|
||||
just holds an expression until it is stored
|
||||
in the runner's macro table.
|
||||
"""
|
||||
|
||||
@staticmethod
|
||||
def from_parse(result):
|
||||
return macro_expression(
|
||||
result[0].name,
|
||||
result[1]
|
||||
)
|
||||
|
||||
def set_runner(self, runner):
|
||||
self.expr.set_runner(runner)
|
||||
|
||||
def bind_variables(self, *, ban_macro_name: str | None = None):
|
||||
self.expr.bind_variables(ban_macro_name = ban_macro_name)
|
||||
|
||||
def __init__(self, label: str, expr: LambdaToken):
|
||||
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}"
|
||||
|
||||
|
||||
class bound_variable(LambdaToken):
|
||||
def __init__(self, name: str, *, runner, forced_id = None):
|
||||
self.original_name = name
|
||||
self.runner = runner
|
||||
|
||||
if forced_id is None:
|
||||
self.identifier = self.runner.bound_variable_counter
|
||||
self.runner.bound_variable_counter += 1
|
||||
else:
|
||||
self.identifier = forced_id
|
||||
|
||||
def __eq__(self, other):
|
||||
if not isinstance(other, bound_variable):
|
||||
raise TypeError(f"Cannot compare bound_variable with {type(other)}")
|
||||
return self.identifier == other.identifier
|
||||
|
||||
def __repr__(self):
|
||||
return f"<{self.original_name} {self.identifier}>"
|
||||
|
||||
def __str__(self):
|
||||
return self.original_name
|
||||
|
||||
class lambda_func(LambdaToken):
|
||||
"""
|
||||
Represents a function.
|
||||
Defined like λa.aa
|
||||
|
||||
After being created by the parser, a function
|
||||
needs to have its variables bound. This cannot
|
||||
happen during parsing, since the parser creates
|
||||
functions "inside-out," and we need all inner
|
||||
functions before we bind variables.
|
||||
"""
|
||||
|
||||
@staticmethod
|
||||
def from_parse(result):
|
||||
if len(result[0]) == 1:
|
||||
return lambda_func(
|
||||
result[0][0],
|
||||
result[1]
|
||||
)
|
||||
else:
|
||||
return lambda_func(
|
||||
result[0].pop(0),
|
||||
lambda_func.from_parse(result)
|
||||
)
|
||||
|
||||
def set_runner(self, runner):
|
||||
self.runner = runner
|
||||
self.input.set_runner(runner)
|
||||
self.output.set_runner(runner)
|
||||
|
||||
def __init__(
|
||||
self,
|
||||
input_var: macro | bound_variable,
|
||||
output: LambdaToken
|
||||
):
|
||||
self.input: macro | bound_variable = input_var
|
||||
self.output: LambdaToken = output
|
||||
|
||||
def __repr__(self) -> str:
|
||||
return f"<{self.input!r} → {self.output!r}>"
|
||||
|
||||
def __str__(self) -> str:
|
||||
return f"λ{self.input}.{self.output}"
|
||||
|
||||
def bind_variables(
|
||||
self,
|
||||
placeholder: macro | None = None,
|
||||
val: bound_variable | None = None,
|
||||
*,
|
||||
binding_self: bool = False,
|
||||
ban_macro_name: str | None = None
|
||||
) -> None:
|
||||
"""
|
||||
Go through this function and all the functions inside it,
|
||||
and replace the strings generated by the parser with bound
|
||||
variables or free variables.
|
||||
|
||||
If values are passed to `placeholder` and `val,`
|
||||
we're binding the variable of a function containing
|
||||
this one. If they are both none, start the binding
|
||||
chain with this function.
|
||||
|
||||
If only one of those arguments is None, something is very wrong.
|
||||
|
||||
`placeholder` is a macro, NOT A STRING!
|
||||
The parser assumes all names are macros at first, variable
|
||||
binding fixes those that are actually bound variables.
|
||||
|
||||
If `binding_self` is True, don't throw an error on a name conflict
|
||||
and don't bind this function's input variable.
|
||||
This is used when we're calling this method to bind this function's
|
||||
variable.
|
||||
"""
|
||||
|
||||
|
||||
if (placeholder is None) and (val != placeholder):
|
||||
raise Exception(
|
||||
"Error while binding variables: placeholder and val are both None."
|
||||
)
|
||||
|
||||
# We only need to check for collisions if we're
|
||||
# binding another function's variable. If this
|
||||
# function starts the bind chain, skip that step.
|
||||
if placeholder is not None:
|
||||
if not binding_self and isinstance(self.input, macro):
|
||||
if self.input == placeholder:
|
||||
raise ReductionError(f"Bound variable name conflict: \"{self.input.name}\"")
|
||||
|
||||
if self.input.name in self.runner.macro_table:
|
||||
raise ReductionError(f"Bound variable name conflict: \"{self.input.name}\" is a macro")
|
||||
|
||||
|
||||
# If this function's variables haven't been bound yet,
|
||||
# bind them BEFORE binding the outer function's.
|
||||
#
|
||||
# If we bind inner functions' variables before outer
|
||||
# functions' variables, we won't be able to detect
|
||||
# name conflicts.
|
||||
if isinstance(self.input, macro) and not binding_self:
|
||||
new_bound_var = bound_variable(
|
||||
self.input.name,
|
||||
runner = self.runner
|
||||
)
|
||||
self.bind_variables(
|
||||
self.input,
|
||||
new_bound_var,
|
||||
binding_self = True,
|
||||
ban_macro_name = ban_macro_name
|
||||
)
|
||||
self.input = new_bound_var
|
||||
|
||||
|
||||
# Bind variables inside this function.
|
||||
if isinstance(self.output, macro) and placeholder is not None:
|
||||
if self.output.name == ban_macro_name:
|
||||
raise ReductionError(f"Cannot use macro \"{ban_macro_name}\" here.")
|
||||
if self.output == placeholder:
|
||||
self.output = val # type: ignore
|
||||
elif isinstance(self.output, lambda_func):
|
||||
self.output.bind_variables(placeholder, val, ban_macro_name = ban_macro_name)
|
||||
elif isinstance(self.output, lambda_apply):
|
||||
self.output.bind_variables(placeholder, val, ban_macro_name = ban_macro_name)
|
||||
|
||||
def reduce(self) -> ReductionStatus:
|
||||
|
||||
r = self.output.reduce()
|
||||
|
|
@ -442,88 +164,6 @@ class lambda_func(LambdaToken):
|
|||
|
||||
|
||||
class lambda_apply(LambdaToken):
|
||||
"""
|
||||
Represents a function application.
|
||||
Has two elements: fn, the function,
|
||||
and arg, the thing it acts upon.
|
||||
|
||||
Parentheses are handled by the parser, and
|
||||
chained functions are handled by from_parse.
|
||||
"""
|
||||
|
||||
@staticmethod
|
||||
def from_parse(result):
|
||||
if len(result) == 2:
|
||||
return lambda_apply(
|
||||
result[0],
|
||||
result[1]
|
||||
)
|
||||
elif len(result) > 2:
|
||||
return lambda_apply.from_parse([
|
||||
lambda_apply(
|
||||
result[0],
|
||||
result[1]
|
||||
)] + result[2:]
|
||||
)
|
||||
|
||||
def set_runner(self, runner):
|
||||
self.runner = runner
|
||||
self.fn.set_runner(runner)
|
||||
self.arg.set_runner(runner)
|
||||
|
||||
def __init__(
|
||||
self,
|
||||
fn: LambdaToken,
|
||||
arg: LambdaToken
|
||||
):
|
||||
self.fn: LambdaToken = fn
|
||||
self.arg: LambdaToken = arg
|
||||
|
||||
def __repr__(self) -> str:
|
||||
return f"<{self.fn!r} | {self.arg!r}>"
|
||||
|
||||
def __str__(self) -> str:
|
||||
return f"({self.fn} {self.arg})"
|
||||
|
||||
def bind_variables(
|
||||
self,
|
||||
placeholder: macro | None = None,
|
||||
val: bound_variable | None = None,
|
||||
*,
|
||||
ban_macro_name: str | None = None
|
||||
) -> None:
|
||||
"""
|
||||
Does exactly what lambda_func.bind_variables does,
|
||||
but acts on applications instead.
|
||||
"""
|
||||
|
||||
if (placeholder is None) and (val != placeholder):
|
||||
raise Exception(
|
||||
"Error while binding variables: placeholder and val are both None."
|
||||
)
|
||||
|
||||
# If val and placeholder are None,
|
||||
# everything below should still work as expected.
|
||||
if isinstance(self.fn, macro) and placeholder is not None:
|
||||
if self.fn.name == ban_macro_name:
|
||||
raise ReductionError(f"Cannot use macro \"{ban_macro_name}\" here.")
|
||||
if self.fn == placeholder:
|
||||
self.fn = val # type: ignore
|
||||
elif isinstance(self.fn, lambda_func):
|
||||
self.fn.bind_variables(placeholder, val, ban_macro_name = ban_macro_name)
|
||||
elif isinstance(self.fn, lambda_apply):
|
||||
self.fn.bind_variables(placeholder, val, ban_macro_name = ban_macro_name)
|
||||
|
||||
if isinstance(self.arg, macro) and placeholder is not None:
|
||||
if self.arg.name == ban_macro_name:
|
||||
raise ReductionError(f"Cannot use macro \"{ban_macro_name}\" here.")
|
||||
if self.arg == placeholder:
|
||||
self.arg = val # type: ignore
|
||||
elif isinstance(self.arg, lambda_func):
|
||||
self.arg.bind_variables(placeholder, val, ban_macro_name = ban_macro_name)
|
||||
elif isinstance(self.arg, lambda_apply):
|
||||
self.arg.bind_variables(placeholder, val, ban_macro_name = ban_macro_name)
|
||||
|
||||
def sub_bound_var(
|
||||
self,
|
||||
val,
|
||||
|
|
|
|||
Reference in New Issue