c++ - why simple grammar rule in bison not working? -

i learning flex & bison , stuck here , cannot figure out how such simple grammar rule not work expected, below lexer code:

%{  #include <stdio.h> #include "zparser.tab.h"  %}  %%  [\t\n ]+        //ignore white space  from|from           { return from;   } select|select       { return select; } update|update       { return update; } insert|insert       { return insert; } delete|delete       { return delete; } [a-za-z].*          { return identifier; } \*                  { return star;   }  %% 

and below parser code:

%{ #include<stdio.h> #include<iostream> #include<vector> #include<string> using namespace std;  extern int yyerror(const char* str); extern int yylex();   %}  %%  %token select update insert delete star identifier from;   zql     : select star  identifier { cout<<"done"<<endl; return 0;}         ;  %% 

can 1 tell me why shows error if try put "select * something"

[a-za-z].* { return identifier; }

the problem here. allows junk follow initial alpha character , returned identifier, including in case entire rest of line after initial ''s.

it should be:

[a-za-z]+          { return identifier; } 

or possibly

[a-za-z][a-za-z0-9]*          { return identifier; } 

or whatever else want allow follow initial alpha character in identifiers.