101 lines
2.5 KiB
Python
101 lines
2.5 KiB
Python
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import pyparsing as pp
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# Packrat gives a significant speed boost.
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pp.ParserElement.enablePackrat()
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class LambdaParser:
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def make_parser(self):
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self.lp = pp.Suppress("(")
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self.rp = pp.Suppress(")")
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self.pp_expr = pp.Forward()
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# Bound variables are ALWAYS lowercase and single-character.
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# We still create macro objects from them, they are turned into
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# bound variables after the expression is built.
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self.pp_macro = pp.Word(pp.alphas + "_")
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self.pp_bound = pp.Regex("[a-z][₀₁₂₃₄₅₆₈₉]*")
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self.pp_name = self.pp_bound ^ self.pp_macro
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self.pp_church = pp.Word(pp.nums)
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self.pp_history = pp.Char("$")
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# Function calls.
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#
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# <exp> <exp>
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# <exp> <exp> <exp>
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self.pp_call = pp.Forward()
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self.pp_call <<= (self.pp_expr | self.pp_bound | self.pp_history)[2, ...]
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# Function definitions, right associative.
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# Function args MUST be lowercase.
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#
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# <var> => <exp>
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self.pp_lambda_fun = (
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(pp.Suppress("λ") | pp.Suppress("\\")) +
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pp.Group(self.pp_bound[1, ...]) +
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pp.Suppress(".") +
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(self.pp_expr ^ self.pp_call)
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)
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# Assignment.
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# Can only be found at the start of a line.
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#
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# <name> = <exp>
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self.pp_macro_def = (
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pp.line_start() +
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self.pp_macro +
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pp.Suppress("=") +
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(self.pp_expr ^ self.pp_call ^ self.pp_history)
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)
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self.pp_expr <<= (
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self.pp_church ^
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self.pp_lambda_fun ^
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self.pp_name ^
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(self.lp + self.pp_expr + self.rp) ^
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(self.lp + self.pp_call + self.rp) ^
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(self.lp + self.pp_history + self.rp)
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)
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self.pp_command = pp.Suppress(":") + pp.Word(pp.alphas + "_") + pp.Word(pp.alphas + pp.nums + "_.")[0, ...]
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self.pp_all = (
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self.pp_expr ^
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self.pp_macro_def ^
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self.pp_command ^
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self.pp_call ^
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self.pp_history
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)
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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_func,
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action_bound,
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action_macro,
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action_call,
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action_history
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):
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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_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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self.pp_call.set_parse_action(action_call)
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self.pp_history.set_parse_action(action_history)
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def parse_line(self, line: str):
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return self.pp_all.parse_string(
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line,
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parse_all = True
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)[0]
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def run_tests(self, lines: list[str]):
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return self.pp_all.run_tests(lines)
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