d436e09d07
Test Plan: . Reviewers: xymostech Reviewed By: xymostech Differential Revision: http://phabricator.benalpert.com/D33
88 lines
2.0 KiB
Plaintext
88 lines
2.0 KiB
Plaintext
/* 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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cdot return 'CDOT'
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frac return 'FRAC'
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lvert return 'LVERT'
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rvert return 'RVERT'
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[/|a-zA-Z0-9] return 'ORD'
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[*+-] return 'BIN'
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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 'OPEN'
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[)] return 'CLOSE'
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[\\] return '\\'
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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 'ORD'
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%left 'BIN'
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%left SUPSUB
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%start expression
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%% /* language grammar */
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expression
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: ex EOF
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{return $1;}
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;
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ex
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:
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{$$ = [];}
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| group ex
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{$$ = $1.concat($2);}
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| group '^' group ex
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{$$ = [{type: 'sup', value: {base: $1, sup: $3}}].concat($4);}
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| group '_' group ex
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{$$ = [{type: 'sub', value: {base: $1, sub: $3}}].concat($4);}
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| group '^' group '_' group ex %prec SUPSUB
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{$$ = [{type: 'supsub', value: {base: $1, sup: $3, sub: $5}}].concat($6);}
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| group '_' group '^' group ex %prec SUPSUB
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{$$ = [{type: 'supsub', value: {base: $1, sup: $5, sub: $3}}].concat($6);}
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;
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group
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: atom
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{$$ = $1;}
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| '{' ex '}'
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{$$ = $2;}
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| '\\' func
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{$$ = $2;}
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;
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func
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: 'CDOT'
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{$$ = [{type: 'bin', value: yytext}];}
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| 'FRAC' group group
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{$$ = [{type: 'frac', value: {numer: $2, denom: $3}}];}
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| 'LVERT'
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{$$ = [{type: 'open', value: yytext}];}
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| 'RVERT'
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{$$ = [{type: 'close', value: yytext}];}
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;
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atom
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: 'ORD'
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{$$ = [{type: 'ord', value: yytext}];}
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| 'BIN'
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{$$ = [{type: 'bin', value: yytext}];}
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| 'OPEN'
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{$$ = [{type: 'open', value: yytext}];}
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| 'CLOSE'
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{$$ = [{type: 'close', value: yytext}];}
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;
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