Re: Please help!....Strange Error

[Tim Van Holder]

> %start exp_line
> 
> %%
> 
> exp_line : if_exp NEWLINE
>          | '}' NEWLINE
>          | PORTS NEWLINE
>          | NEWLINE 
>          | '!' NEWLINE 
> | error NEWLINE 
>          ;

Your start rule only matches the one line.
What you probably want is to add another rule:

%start commands

commands
: /* empty */
| commands exp_line
;

(if you expect at least one command, change the /* empty */ to exp_line).
Note that in cases like this it can help to #define YYERROR_VERBOSE, as
that will (in most cases) tell you what tokens were expected when there is
a parse error.

As an aside, you may want to consider the style I used above to keep your
bison files more readable. Consider:

if_exp
: exp
  {
    $$ = $1;
    //printf("if_exp->$1: %d\n", $<y_int>1);
  }
| var_exp '?' if_exp ':' if_exp
  {
    //$<y_tree>$ = make_op2_node(P_IF, $<y_tree>1,
    //                           make_op2_node(P_CON, $<y_tree>3,
$<y_tree>5));
    //$$ = new Tree(P_IF, $<y_tree>1, new Tree(P_CON, $<y_tree>3,
$<y_tree>5));
    $$ = $1;
  }
| var_exp '#' if_exp
  {
    //$<y_tree>$ = make_op2_node(P_ITER, $<y_tree>1, $<y_tree>3);
    $$ = new Tree(ITER_OpCode, $1, $3);
  }
| WHILE_DO var_exp ',' var_exp ')'
  {
    //$<y_tree>$ = make_op2_node(P_WHILE, $<y_tree>2, $<y_tree>4);
    $$ = new Tree(WHILE_OpCode, $2, $4);
  }
;

instead of

> if_exp : exp 
>        { 
>        $$ = $1; 
>        //printf("if_exp->$1: %d\n",$<y_int>1);
>        }
>        | var_exp '?' if_exp ':' if_exp
>           {
>           //$<y_tree>$ = make_op2_node(P_IF,$<y_tree>1,
>             //              
> make_op2_node(P_CON,$<y_tree>3,$<y_tree>5));
>           //   $$ = new Tree(P_IF,$<y_tree>1, new 
> Tree(P_CON,$<y_tree>3,$<y_tree>5));
>           $$ = $1; 
>           }
>        | var_exp '#' if_exp
>           {
>             //$<y_tree>$ = 
> make_op2_node(P_ITER,$<y_tree>1,$<y_tree>3);
>           $$ = new Tree(ITER_OpCode,$1,$3);
>           }
>        | WHILE_DO var_exp ',' var_exp ')'
>           {
>           //$<y_tree>$ = make_op2_node(P_WHILE,$<y_tree>2,$<y_tree>4);
>           $$ = new Tree(WHILE_OpCode,$2,$4);
>           } 
>        ;

Also, you may want to consider typing your rules to avoid having to use
$<y_tree>n constructs.