On Thursday, 26 February 2015 at 12:39:20 UTC, Laeeth Isharc wrote:
> Hi John.
>
> Tks help with ldc - will look at that shortly.
>
> So Kingsly needs to use a predicate for canFind that returns true if the two values being compared are close enough to being the same given floating point quirks ?
>
> Ie I think people diagnosed the problem, but what is the solution...

My preference would be to find a way to construct the program such that it isn't needed.

Failing that, std.math has feqrl and approxEqual for this task.

Thanks.

Rough version for Wiki here:
http://wiki.dlang.org/Floating_Point_Gotchas

It could be tidier, but I am not able to do so at moment.  Feel free to change.

On Thursday, 26 February 2015 at 14:04:17 UTC, John Colvin wrote:
> On Thursday, 26 February 2015 at 12:39:20 UTC, Laeeth Isharc wrote:
>> Hi John.
>>
>> Tks help with ldc - will look at that shortly.
>>
>> So Kingsly needs to use a predicate for canFind that returns true if the two values being compared are close enough to being the same given floating point quirks ?
>>
>> Ie I think people diagnosed the problem, but what is the solution...
>
> My preference would be to find a way to construct the program such that it isn't needed.
>
> Failing that, std.math has feqrl and approxEqual for this task.

>     immutable float item = 0.174531f;
>     r.canFind!q{ feqrel(cast()a, cast()b) >= 21 }(item).writeln;
> }

With a recent Phobos bug fix you can now write:

    r.canFind!q{ feqrel(a, b) >= 21 }(item).writeln;

Bye,
bearophile