41 lines
1.2 KiB
Factor
41 lines
1.2 KiB
Factor
#! An interpreter for lambda expressions, by Matthew Willis
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REQUIRES: lazy-lists ;
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USING: lazy-lists io strings hashtables sequences namespaces kernel ;
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IN: lambda
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: bound-vars ( -- lazy-list ) 65 lfrom [ ch>string ] lmap ;
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: canonical-string ( expr -- string )
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#! pretty print in canonical form, for use with reverse lookups
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bound-vars swap expr>string ;
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: original-string ( expr -- string )
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#! pretty print with vars named as inputed
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nil swap expr>string ;
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: lambda-print ( names expr/name -- names )
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dup string? [ over dupd hash original-string " " swap
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append append "DEF " swap append
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] [ original-string "=> " swap append
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] if print flush ;
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: lambda-eval ( names parse-result -- names name/expr )
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#! Make sure not to evaluate definitions.
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first2 over [
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swap rot [ set-hash ] 2keep swap
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] [
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pick swap replace-names swap drop evaluate
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] if ;
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: lambda-boot ( -- names )
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#! load the core lambda library
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H{ } clone dup lambda-core
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[ lambda-parse lambda-eval lambda-print drop ] each-with ;
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: (lambda) ( names -- names )
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readln dup "." = [ drop ] [
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lambda-parse lambda-eval lambda-print (lambda)
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] if ;
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: lambda ( -- names )
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lambda-boot (lambda) ; |