On Tuesday, 25 March 2014 at 20:37:31 UTC, Nordlöw wrote:
Correction:
I guess typeof return value could be deduced according + and *
at least.
Return type is of course obvious, value is not...
The return type is not actually obvious. You'd think:
alias S = typeof(fun(r.front, r.front));
S s;
Which is a good start. But then
is (S == typeof(fun(s, r.front))) ?
You have no guarantees that you'll have "stability" of the
returned type.
More often than not, it *is* stable, but there are cases where it
is not.
This is not a huge problem, because the consequence is simply
that it fails to compile. We can simply catch it, and tell the
user to provide an explicit seed, so as to help out the function.
But as you said, for the value, the is simply no correct initial
value, unless you know the "identity" value of your operator. But
even then, that value makes no sense is the range is empty.
