Re: foreach interation over specified index values in multiple index arrays

[Mike Mason <mmlnx at us dot ibm dot com>]

Frank Ch. Eigler wrote:
> Mike Mason <mmlnx@us.ibm.com> writes:
>
> > [...]
> > 	// stap doesn't like the 3 in foreach
> >         foreach ([3, idx2] in arr) {
> >                 printf("%s\n", arr[3, idx2])
> >         }
> > [...]
>
> We could support this syntax (interpreting literals as
> select/project).  However, it would not be efficient to implement,
> since all keys are hashed together for the array indexing.  It would
> be equivalent to
>
> #         foreach ([__idx1, idx2] in arr) {
> #                 if (__idx1 != 3) continue
> #                 printf("%s\n", arr[3, idx2])
> #         }

We can do this already, so if it can't be more efficient, I vote to leave the syntax as is.  I'd rather not hide the inefficiency behind syntax changes, especially when traversing large multi-index arrays.  Script writers need to know what's really happening. 

I mainly ask because I thought I might be missing something.  Would be a nice feature, but it's not high on my list.

Thanks,
Mike

> - FChE