61 lines
1.2 KiB
Text
61 lines
1.2 KiB
Text
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/* description: Parses end executes mathematical expressions. */
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/* lexical grammar */
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%lex
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%%
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\s+ /* skip whitespace */
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[0-9]+("."[0-9]+)?\b return 'NUMBER';
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"*" return '*';
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"/" return '/';
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"-" return '-';
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"+" return '+';
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"^" return '^';
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"(" return '(';
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")" return ')';
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"PI" return 'PI';
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"E" return 'E';
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<<EOF>> return 'EOF';
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/lex
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/* operator associations and precedence */
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%left '+' '-'
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%left '*' '/'
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%left '^'
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%left UMINUS
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%start expressions
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%% /* language grammar */
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expressions
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: e EOF
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{print($1); return $1;}
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;
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e
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: e '+' e
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{$$ = $1+$3;}
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| e '-' e
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{$$ = $1-$3;}
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| e '*' e
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{$$ = $1*$3;}
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| e '/' e
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{$$ = $1/$3;}
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| e '^' e
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{$$ = Math.pow($1, $3);}
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| '-' e %prec UMINUS
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{$$ = -$2;}
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| '(' e ')'
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{$$ = $2;}
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| NUMBER
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{$$ = Number(yytext);}
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| E
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{$$ = Math.E;}
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| PI
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{$$ = Math.PI;}
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;
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/* From https://gerhobbelt.github.io/jison/docs/#specifying-a-language */
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