[Issue 8882] map, filter, iota and zip in pure (and nothrow) functions

[d-bugmail at puremagic.com]

https://d.puremagic.com/issues/show_bug.cgi?id=8882


monarchdodra at gmail.com changed:

           What    |Removed                     |Added
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                 CC|                            |monarchdodra at gmail.com


--- Comment #4 from monarchdodra at gmail.com 2014-01-16 11:58:06 PST ---
(In reply to comment #2)
> The situation has now improved:

Yeah, thanks Kenji!

> zip can throw because of StoppingPolicy.requireSameLength, and iota(x,y,z)
> throws when z can be 0. iota(x) and iota(x,y) are nothrow.
> 
> I think the problem with zip() can be solved introducing an api change, or
> adding a new zip overload that takes StoppingPolicy as first template argument.

Yes, having a run-time condition is awful IMO. It should always be know compile
time. It can also create subtle issues for things such as "hasSlicing", which
only works for certain stopping tipes.

> Fixing iota(x,y,z) is less easy. z is often a value known at compile time, so
> in theory a new version of iota!z(x, y) can be nothrow at run-time.
> 
> even iota(x,y) is not nothrow for floating point arguments:
> 
> 
> import std.range: iota;
> void main() nothrow {
>     iota(1.0, 2.0);
> }
> 
> test.d(3): Error: 'std.range.iota!(double, double).iota' is not nothrow
> test.d(2): Error: function 'D main' is nothrow yet may throw

Bah, I think illegal input should Error. Problem solved.

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