+ EBNF Mode (bracesMode setting = "javascript") + +/* description: Parses end executes mathematical expressions. */ + +/* lexical grammar */ +%lex + +%% +\s+ /* skip whitespace */ +[0-9]+("."[0-9]+)?\b return 'NUMBER'; +"*" return '*'; +"/" return '/'; +"-" return '-'; +"+" return '+'; +"^" return '^'; +"(" return '('; +")" return ')'; +"PI" return 'PI'; +"E" return 'E'; +<<EOF>> return 'EOF'; + +/lex + +/* operator associations and precedence */ + +%left '+' '-' +%left '*' '/' +%left '^' +%left UMINUS + +%start expressions + +%% /* language grammar */ + +expressions +: e EOF +{print($1); return $1;} +; + +e +: e '+' e +{$$ = $1+$3;} +| e '-' e +{$$ = $1-$3;} +| e '*' e +{$$ = $1*$3;} +| e '/' e +{$$ = $1/$3;} +| e '^' e +{$$ = Math.pow($1, $3);} +| '-' e %prec UMINUS +{$$ = -$2;} +| '(' e ')' +{$$ = $2;} +| NUMBER +{$$ = Number(yytext);} +| E +{$$ = Math.E;} +| PI +{$$ = Math.PI;} +; + + The EBNF Mode + Created by Robert Plummer +
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