TDPL: Overloading template functions

[Andrej Mitrovic]

These templates seem to be hard to get right. I guess with experience they
get easier to write and comprehend. Anyways, thanks for the explanation.

On Wed, Jul 28, 2010 at 4:44 PM, Philippe Sigaud
<philippe.sigaud at gmail.com>wrote:

> On Wed, Jul 28, 2010 at 05:50, Andrej Mitrovic <andrej.mitrovich at gmail.com
> > wrote:
>
> I won't comment on the double/float issue, I do not anything about it.
>
>
>> T[] find(T, E)(T[] haystack, E needle)
>>    if (is(typeof(haystack[0] != needle) == bool))
>>
>> T1[] find(T1, T2)(T1[] longer, T2[] shorter)
>>    if (is(typeof(longer[0 .. 1] == shorter) : bool))
>>
>> Also, Andrei, you never explained the if(is()) signature of the second
>> templated function. I hope to get some pointers on that. :)
>>
>
> I'll have a try at this one.
> As you may know, the is(typeof()) syntax is a way to try to compile an
> expression and see if it works. If it works, it has a type, given by typeof
> and is(Type) returns true. So the first one is really saying: "Hey compiler,
> may I compare an element of haystack (of type T) with an E
> In this case, longer is an array. So longer[0] would be an element, a T1.
> There is no chance that shorter will match as an element cannot be equal to
> an array ... except, of course, if longer is an array of T2[]  (T1 == T2[]).
> Longer is a T2[][]. That may happen for arrays of strings, strings being
> arrays of chars. And I think that's the problem you have in your last unit
> test.
>
> Anyway, he takes longer[0..1] to get a slice, which is a dynamic array, a
> T1[] and hence comparable to a T2[]... most of the time.
>
> As for using ': bool' instead of '== bool' as in the first find(),  I don't
> think there is any difference in this case. I understand T == U as 'T is the
> exact same type as U', whereas T : U is for me "T is a subtype of U". But
> then, a subtype of bool is pretty much constrained to be a bool. The T : U
> syntax is pretty much only used for classes : if(is(T : MyClass)) is saying
> : 'compile this only if T is a subclass of MyClass'.
>
>
> Philippe
>
>
>
> , except if longer is in fact
>
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