how to write custom function and variable in jison?

Question

my lex code is

/* description: Parses end executes mathematical expressions. */

/* lexical grammar */
%lex
%%

\s+                   /* skip whitespace */
[0-9]+("."[0-9]+)?\b  return 'NUMBER'
[a-zA-Z]              return 'FUNCTION'
  <<EOF>>               return 'EOF'
.                     return 'INVALID'

/lex

/* operator associations and precedence */

%start expressions

%% /* language grammar */

expressions
    : e EOF
        {return $1;}
    ;

e
    | FUNCTION '('e')'
      {$$=$3}
    | NUMBER
        {$$ = Number(yytext);}
    ;

i got error

Parse error on line 1:
balaji()
-^
Expecting '(', got 'FUNCTION'

what i want to pass myfun(a,b,...) and also myfun(a) in this parser.thank you for your valuable time going to spent for me.

Answer 1

[a-zA-Z] matches a single alphabetic character (in this case, the letter b), returning FUNCTION. When the next token is needed, it again matches a single alphabetic character (a), returning another FUNCTION token. But of course the grammar doesn't allow two consecutive FUNCTIONs; it's expecting a (, as it says.

You probably intended [a-zA-Z]+, although a better identifier pattern is [A-Za-z_][A-Za-z0-9_]*, which matches things like my_function_2.