70 lines
2.0 KiB
Factor
70 lines
2.0 KiB
Factor
#! 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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USING: lazy-lists parser-combinators strings sequences kernel ;
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IN: lambda
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LAZY: <letter>
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#! parses an uppercase or lowercase letter
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[ letter? ] satisfy [ 1string ] <@ ;
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LAZY: <LETTER>
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#! parses an uppercase or lowercase letter
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[ LETTER? ] satisfy [ 1string ] <@ ;
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LAZY: <number>
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#! parses a number
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[ digit? ] satisfy [ 1string ] <@ ;
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LAZY: <alphanumeric>
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#! parses an alphanumeral
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<letter> <number> <|> ;
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LAZY: <ALPHANUMERIC>
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#! parses an alphanumeral
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<LETTER> <number> <|> ;
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LAZY: <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 <var-node> ] <@ ;
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LAZY: <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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LAZY: <lambda> ( -- parser )
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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 var-node-name ] keep second <lambda-node> ] <@ ;
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LAZY: <apply> ( -- parser )
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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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LAZY: <alien> ( -- parser )
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#! parses [<FACTOR-WORD>], the alien invocation
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#! an alien factor word must be all capital letters and numerals
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"[" token <name> sp &> "]" token sp <& [ <alien-node> ] <@ ;
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LAZY: <expr>
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<id> <lambda> <apply> <|> <|>
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<name> [ <var-node> ] <@ <|> <alien> <|> ;
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LAZY: <line>
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":" token <name> &> <expr> sp <&> f succeed <expr> <&>
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<|> "." token <name> &> f succeed <&> <|> ;
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: lambda-parse
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<line> some parse force ; |