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node_modules/shiki/samples/jison.sample

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+/* 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;}
+    ;
+
+/* From https://gerhobbelt.github.io/jison/docs/#specifying-a-language */