Problems with untyped

[John S O'Sullivan]

I would appreciate some trouble with a simple grammar I am trying to
develop. I have attached some sample code.
When I initially compiled this with support for integers it worked fine. I
added the capability to handle floats and ran into trouble. Bison complains
that the line
     |       IF expression '<' expression THEN statement { if ($2 < $4) $6;
} 
has $6 untyped. I can't figure out what type $6 should be. It is a statement
so I assumed it did not need an associated type. I have read the Bison
manual , but find the brief references to typing unclear. I have also
trawled the mailing lists without success.



Grammar file
----------------------------------------------------------------------------
----------------------------------------------------------------------------
-
%{
#include <stdio.h>
#include <string.h>


void yyerror(const char *str)
{
        fprintf(stderr,"error: %s\n",str);
}

int yywrap()
{
        return 1;
}

main()
{
        yyparse();
}



float vbltable[26];

%}

%token IF
%token ELSE
%token THEN
%token ENDIF


%union {
        float dval;
        int vblno;
}


%token <vblno> NAME
%token <dval> NUMBER
%left '-' '+'
%left '*' '/'
%nonassoc UMINUS

%type <dval> expression
%%
statement_list: statement '\n'
        |       statement_list statement '\n'
        ;

statement:      NAME '=' expression     { vbltable[$1] = $3; }  
        |       IF expression '<' expression THEN statement { if ($2 < $4)
$6; }
        |       expression              { printf("= %f\n", $1); }
        ;

expression:     expression '+' expression { $$ = $1 + $3; }
        |       expression '-' expression { $$ = $1 - $3; }
        |       expression '*' expression { $$ = $1 * $3; }
        |       expression '/' expression
                                {       if($3 == 0.0)
                                                yyerror("divide by zero");
                                        else
                                                $$ = $1 / $3;
                                }
        |       '-' expression %prec UMINUS     { $$ = -$2; }
        |       '(' expression ')'      { $$ = $2; }
        |       NUMBER
        |       NAME                    { $$ = vbltable[$1]; }
        ;
%%


----------------------------------------------------------------------------
----------------------------------------------------------------------------
-----------
Lex file
----------------------------------------------------------------------------
--------------------------------------------------
%{
#include "y.tab.h"
#include <math.h>
extern float vbltable[26];
%}

%%

"IF"    { return IF; }
"THEN"  { return THEN; }
"ELSE"  { return ELSE; }
"ENDIF"    { return ENDIF; }
([0-9]+|([0-9]*\.[0-9]+)([eE][-+]?[0-9]+)?) {
        yylval.dval = atof(yytext); return NUMBER;
        }

[ \t]   ;                /* ignore white space */

[a-z]   { yylval.vblno = yytext[0] - 'a'; return NAME; }

"$"     { return 0; /* end of input */ }

\n      |
.       return yytext[0];
%%