68 lines
1.8 KiB
Factor
68 lines
1.8 KiB
Factor
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#! A parser for lambda expressions, by Matthew Willis
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#! The grammar in BNF is:
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#! <expr> ::= <id>
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#! <expr> ::= <name>
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#! <expr> ::= (<id> . <expr>)
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#! <expr> ::= (<expr> <expr>)
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#! <line> ::= <expr>
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#! <line> ::= <name> : <expr>
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REQUIRES: parser-combinators ;
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USING: parser-combinators strings sequences kernel ;
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IN: lambda
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: <letter>
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#! parses an uppercase or lowercase letter
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[ letter? ] satisfy [ ch>string ] <@ ;
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: <LETTER>
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#! parses an uppercase or lowercase letter
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[ LETTER? ] satisfy [ ch>string ] <@ ;
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: <number>
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#! parses a number
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[ digit? ] satisfy [ ch>string ] <@ ;
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: <alphanumeric>
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#! parses an alphanumeral
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<letter> <number> <|> ;
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: <ALPHANUMERIC>
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#! parses an alphanumeral
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<LETTER> <number> <|> ;
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: <id>
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#! parses an identifier (string for now)
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#! TODO: do we need to enter it into a symbol table?
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<letter> <alphanumeric> <*> <&:> [ concat <variable-node> ] <@ ;
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: <name>
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#! parses a name, which is used in replacement
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<ALPHANUMERIC> <+> [ concat ] <@ ;
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DEFER: <expr>
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: <lambda>
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#! parses (<id>.<expr>), the "lambda" expression
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#! all occurences of <id> are replaced with a pointer to this
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#! lambda expression.
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"(" token <id> sp &> "." token sp <&
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<expr> sp <&> ")" token sp <&
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[ [ first variable-node-var ] keep second <lambda-node> ] <@ ;
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: <apply>
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#! parses (<expr> <expr>), the function application
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"(" token <expr> sp &> <expr> sp <&> ")" token sp <&
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[ [ first ] keep second <apply-node> ] <@ ;
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: <expr>
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[ <id> call ] [ <lambda> call ] [ <apply> call ] <|> <|>
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<name> [ <variable-node> ] <@ <|> ;
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: <line>
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":" token <name> &> <expr> sp <&> "OK" succeed <expr> <&>
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<|> ;
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: lambda-parse
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#! debug word to parse this <expr> and print the result
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<line> some call ;
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