(j3.2006) 17-152 and CO_REDUCE

[Malcolm Cohen]

>If the processor is expected to enforce the requirements on OPERATION, it
should be required to have explicit interface.

And it is so required:
  C1590 If a procedure that is neither an intrinsic procedure nor a
statement function is used in a context that requires it to be pure, then
its interface shall be explicit in the scope of that use. The interface
shall specify that the procedure is pure.

Cheers,
-- 
,,,,,,,,,,,,,,,,,,,Malcolm.