Re: Inline VALOF

["D.C.Wood" <D.C.Wood@xxxxxxxxxx>]

>occam expressions are very powerful: side-effect free, able to be reasoned
>about simply, able to be parallelised trivially.  Conditional expressions
>would increase that power and I've always fancied them - e.g.:

>  <boolean-exp> -> <exp>, <exp>

>Indeed, we put "->" into the compiler ages ago as a reserved symbol with
>the above in mind ... but never got around to it.  Then, instead of:

>  IF
>    urgent
>      delay := 1*weeks
>    TRUE
>      delay := 2*weeks
>    
>we could write:

>  delay := urgent -> 1*weeks, 2*weeks

>which kind of thing happens quite a lot!??

>I don't see any semantic problem with conditional expressions - the two
>expressions on the RHS must have, of course, matching types.

Since we added user-defined operators, you can write:

INT INLINE FUNCTION "??" (VAL BOOL b, VAL [2]INT x) IS x[INT b]:

(overloaded for any types you like), and then

  delay := (urgent ?? [1, 2]) * weeks

The only problem I can think of is that both expressions (1 and 2 above)
are evaluated.

(And that it's the wrong way round -- make that x[1 - (INT b)] or
x[INT (NOT b)].)

	David