65 lines
1.6 KiB
Python
65 lines
1.6 KiB
Python
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import pyparsing as pp
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import tokens
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class Parser:
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"""
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Macro_def must be on its own line.
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macro_def :: var = expr
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var :: word
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lambda_fun :: var -> expr
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call :: '(' (var | expr) ')' +
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expr :: define | var | call | '(' expr ')'
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"""
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lp = pp.Suppress("(")
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rp = pp.Suppress(")")
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func_char = pp.Suppress("->")
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macro_char = pp.Suppress("=")
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# Simple tokens
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pp_expr = pp.Forward()
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pp_name = pp.Word(pp.alphas + "_")
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pp_name.set_parse_action(tokens.macro.from_parse)
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# Function definitions.
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# Right associative.
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#
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# <var> => <exp>
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pp_lambda_fun = pp_name + func_char + pp_expr
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pp_lambda_fun.set_parse_action(tokens.lambda_func.from_parse)
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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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# <var> = <exp>
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pp_macro_def = pp.line_start() + pp_name + macro_char + pp_expr
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pp_macro_def.set_parse_action(tokens.macro_expression.from_parse)
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# Function calls.
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# `tokens.lambda_func.from_parse` handles chained calls.
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#
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# <var>(<exp>)
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# <var>(<exp>)(<exp>)(<exp>)
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# (<exp>)(<exp>)
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# (<exp>)(<exp>)(<exp>)(<exp>)
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pp_call = pp.Forward()
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pp_call <<= pp_expr[2, ...]
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pp_call.set_parse_action(tokens.lambda_apply.from_parse)
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pp_expr <<= pp_lambda_fun ^ (lp + pp_expr + rp) ^ pp_name ^ (lp + pp_call + rp)
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pp_all = pp_expr | pp_macro_def
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@staticmethod
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def parse_expression(line):
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return Parser.pp_expr.parse_string(line, parse_all = True)[0]
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@staticmethod
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def parse_assign(line):
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return (
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Parser.pp_macro_def
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).parse_string(line, parse_all = True)[0]
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@staticmethod
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def run_tests(lines):
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return Parser.pp_macro_def.run_tests(lines)
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