Summary: Allow std.math pure function to be used in array
           Product: D
           Version: 2.041
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: DMD

--- Comment #0 from Witold Baryluk <> 2010-01-31 
10:22:37 PST ---
It would be good to have possibility to use something like:
  a[] = sin(b[]);

To perform sin function on each element of b.

Or more complicated formulars, like:
  a[] += sin(a[] * b[] + 0.1*x) - x*a[];

I propose that such expression be supported for all relevant operations in
std.math (cos, sin, tan, exp, log, ...).

I also propose to have property "@arrayoperation" for any custom pure function
of T f(T x) pure. which will equivalent to implicitly implementing:

T[] f(T[] x) pure nothrow {
 T[] r = new T[x.length];
 foreach (i, ref y; r) { y = f(x[i]); }
 return r;

which will also be used automatically in array operations expressions and
called automatically by compiler.

There is also need to think about two and more argument functions in std.math,
like pow. For such functions (also pure) i think they should be implemented as

T[] f(T[] a, T[] b) pure nothrow {
 T[] r = new T[x.length];
 foreach (i, ref y; r) { y = f(a[i],b[i]); }
 return r;

Of course temporary array r will not be created if f() will be part of array

Rationale for this is that modern processors have SSE instructions which could
perform up to 4 mathematial operations in parallel (like sin, cos, exp, log,
pow). And one of the reason for array operations is possibility to implement
them this (efficient) way.

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