43 lines
1.2 KiB
Factor
43 lines
1.2 KiB
Factor
USING: accessors kernel locals math math.parser peg.ebnf ;
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IN: rosetta.arith
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TUPLE: operator left right ;
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TUPLE: add < operator ; C: <add> add
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TUPLE: sub < operator ; C: <sub> sub
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TUPLE: mul < operator ; C: <mul> mul
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TUPLE: div < operator ; C: <div> div
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EBNF: expr-ast
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spaces = [\n\t ]*
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digit = [0-9]
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number = (digit)+ => [[ string>number ]]
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value = spaces number:n => [[ n ]]
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| spaces "(" exp:e spaces ")" => [[ e ]]
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fac = fac:a spaces "*" value:b => [[ a b <mul> ]]
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| fac:a spaces "/" value:b => [[ a b <div> ]]
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| value
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exp = exp:a spaces "+" fac:b => [[ a b <add> ]]
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| exp:a spaces "-" fac:b => [[ a b <sub> ]]
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| fac
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main = exp:e spaces !(.) => [[ e ]]
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;EBNF
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GENERIC: eval-ast ( ast -- result )
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M: number eval-ast ;
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: recursive-eval ( ast -- left-result right-result )
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[ left>> eval-ast ] [ right>> eval-ast ] bi ;
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M: add eval-ast recursive-eval + ;
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M: sub eval-ast recursive-eval - ;
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M: mul eval-ast recursive-eval * ;
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M: div eval-ast recursive-eval / ;
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: evaluate ( string -- result )
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expr-ast eval-ast ;
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