Question: I want to design a box with some transparency in it in CSS or CSS3 which must work in IE8, I made this code, it is working fine in other browsers, but in IE8 the box is becoming completely transparent, how to fix this problem?

> 
> 
> ```
> .price_tag {
>     position: absolute;
>     height: 146px;
>     width: 295px;
>     left: 210px;
>     top: 241px;
>     background-color: rgba(221, 221, 221, 0.7);
>     border-radius: 8px;
>     z-index: 200;
> 
>     -webkit-box-shadow: -2px -2px 6px rgba(255,255,255, 1) inset, 2px 0px 4px rgba(255,255,255,1) inset;
> 
>     box-shadow: -2px -2px 6px rgba(255,255,255, 1) inset, 2px 0px 4px rgba(255,255,255,1) inset;
> 
>     behavior: url(pie/PIE.htc); 
> }
> 
> ```
> 
>

Answer: 
With SWI-Prolog and the library(clpfd) you can ask question like that.

```
 ?- use_module(library(clpfd)).
%  library(apply_macros) compiled into apply_macros 0,00 sec, 39 clauses
%  library(assoc) compiled into assoc 0,03 sec, 143 clauses
% library(clpfd) compiled into clpfd 0,11 sec, 1,456 clauses
true.

 ?- 4 #= 2 * X.
X = 2.

```
you can check *instantiation status* of a variable

```
% E is X^Y
% here are accepted patterns
%
% exp(+,+,-)
% exp(-,+,+)
% exp(+,-,+)
%
exp(X,Y,E) :-
     var(E)
  -> E is X^Y % note: will throw an error if either X or Y are not bound to number
  ;  var(X)
  -> compute_base_of_exp_here(Y,E,X) % note: as above, with E in place of X
  ;  var(Y)
  -> (   X =:= e % we are lucky, only natural logarithms are available as ISO builtin
      -> Y is log(X)
      ;  X =:= 2 % again, we could be lucky, log2 can be rather easy to compute...
      -> compute_log2_here(E,Y)
      ;  compute_some_complex_math_here(X,E,Y)
     )
   ; E is X^Y . % no vars? 

```

but this is going to be a rather difficult route, without appropriate builtins...