On Thu, 20 Jan 2011 10:36:00 -0500, foobar <f...@bar.com> wrote:
Jonathan M Davis Wrote:
On Thursday 20 January 2011 03:51:48 Trass3r wrote:
> If such an annotation was introduced, it should be the other way
around.
> But imo discarding a return value should always result in a warning,
> the function returns something for a reason.
Actually, there are plenty of cases where you throw away the return
value. A
number of overloaded operators are prime examples - such as opAssign.
std.algorithm.sort both sorts in place _and_ returns a sorted range (so
that
other algorithms can then know that the range is sorted). It's really
quite easy
to get legitimate cases where throwing away the return value makes
perfect
sense. Now, if you're dealing with a strongly pure function which
throws away
its return value, then yes, that's definitely bug, since the only
effect of the
function is its return value. Frequently however, that's not the case.
Yes, you can have bugs because you didn't actually use the return value
of a
function, but it's that necessarily uncommon to have function calls
which
legitimately throw away their return value.
- Jonathan M Davis
You brought up an interesting idea:
D already supports purity and as you said it doesn't make sense to
discard return values of such functions.
Therefore, it makes sense that for pure functions, this would result in
a compile time error.
Pure functions no longer have that requirement. You can pass mutable
references to pure functions, which makes them weak-pure.
-Steve
