TDPL: Overloading template functions

[Andrej Mitrovic]

They do work if I specify the type before x, as in:
    auto c = find!(function(int x) { return x < 0; })(a);
    auto d = find!((int x) { return x < 0; })(a);


On Wed, Jul 28, 2010 at 11:01 PM, Andrej Mitrovic <
andrej.mitrovich at gmail.com> wrote:

> Page 149, the two shorter-hand ways of writing function literals are not
> working for me:
>
> void main() { }
>
> T[] find(alias pred, T)(T[] input)
>     if (is(typeof(pred(input[0])) == bool))
> {
>     for (; input.length > 0; input = input[1 .. $]) {
>         if (pred(input[0]))
>             break;
>     }
>     return input;
> }
>
> unittest {
>     int[] a = [1, 2, 3, 4, -5, 3, -4];
>
>     auto b = find!(function bool(int x) { return x < 0; })(a);
>     //~ auto c = find!(function(x) { return x < 0; })(a);
>     //~ auto d = find!((x) { return x < 0; })(a);
> }
>
> The first one works fine. But if I uncomment the second or third line I get
> these errors:
>
> higher_order_functions.d(17): Error: template
> higher_order_functions.find(alias pred,T) if (is(typeof(pred(input[0])) ==
> bool)) does not match any function template declaration
>
> higher_order_functions.d(17): Error: template
> higher_order_functions.find(alias pred,T) if (is(typeof(pred(input[0])) ==
> bool)) cannot deduce template function from argument types
> !(__funcliteral1)(int[])
>
>
>
> On Wed, Jul 28, 2010 at 10:44 PM, Andrej Mitrovic <
> andrej.mitrovich at gmail.com> wrote:
>
>> On page 143 there's a new find() overloaded function which is more
>> specialized than the last generic function, but I'm still getting an
>> ambiguity error. Although the book doesn't state if that specific unittest
>> should work, so I'm left wondering :) Here's the code:
>>
>> void main()
>>
>> {
>> }
>>
>> T1[] find(T1, T2)(T1[] longer, T2[] shorter)
>>     if (is(typeof(longer[0 .. 1] == shorter) : bool))
>> {
>>     while (longer.length >= shorter.length) {
>>         if (longer[0 .. shorter.length] == shorter)
>>             break;
>>         longer = longer[1 .. $];
>>     }
>>     return longer;
>> }
>>
>> int[] find(int[] longer, int[] shorter) { }
>>
>> unittest {
>>     int[] ints1 = [1, 2, 3, 5, 2] ;
>>     int[] ints2 = [3, 5];
>>     auto test = find(ints1, ints2);
>> }
>>
>> test.d(16): Error: function test.find conflicts with template
>> test.find(T1,T2) if (is(typeof(longer[0..1] == shorter) : bool)) at
>> test.d(5)
>>
>>
>> And on page 145 the last example is:
>>
>> void main() { }
>>
>> void transmogrify(uint) { }
>> void transmogrify(long) { }
>> void transmogrify(T)(T value) { }
>>
>> unittest {
>>     transmogrify(42);
>>     transmogrify("hello");
>>     transmogrify(1.1);
>> }
>>
>> test2.d(5): Error: template test2.transmogrify(T) conflicts with function
>> test2.transmogrify at test2.d(3)
>>
>>
>> On Wed, Jul 28, 2010 at 7:32 PM, Andrej Mitrovic <
>> andrej.mitrovich at gmail.com> wrote:
>>
>>> Woops, I got confused. I was thinking about structs, not arrays.
>>>
>>> But yeah, in this case a float gets compared to a double and it seems to
>>> evaluate to false.
>>>
>>>
>>> On Wed, Jul 28, 2010 at 7:26 PM, Jonathan M Davis <jmdavisprog at gmail.com
>>> > wrote:
>>>
>>>> On Wednesday, July 28, 2010 09:49:52 Andrej Mitrovic wrote:
>>>> > IIRC arrays are value types and as such they are compared bit-by-bit
>>>> > to each other, right?
>>>>
>>>> Dynamic arrays are reference types (though static arrays are indeed
>>>> value
>>>> types), and they evaluate for equality by comparing each element in turn
>>>> (though
>>>> presumably, they compare their length first and don't bother with
>>>> element
>>>> comparisons if the lengths don't match). Look at section 4.1.5 on page
>>>> 100 of
>>>> TDPL.
>>>>
>>>> - Jonathan M Davis
>>>>
>>>
>>>
>>
>
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