CodeMirror

/* 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;}

;