On Friday, 19 June 2015 at 14:04:05 UTC, Daniel Kozák wrote:
>
> On Fri, 19 Jun 2015 13:52:52 +0000
> Quentin Ladeveze via Digitalmars-d-learn
> <digitalmars-d-learn@puremagic.com> wrote:
>
>> On Friday, 19 June 2015 at 13:38:45 UTC, Steven Schveighoffer wrote:
>> >
>> > Does this work for you, or is there a further expectation?
>> >
>> > auto asTuple() { return Tuple!(int, "a", ...)(a, b, stringValue);}
>> >
>> > -Steve
>> 
>> In fact, I was trying to use traits to create the tuple
>> automatically and being able to add or remove methods to the
>> struct without breaking the asTuple method.
>> I used allMembers for the name of the methods, but I didn't found
>> anything for their return types or their values.
>> 
>> Thank you.
> http://dlang.org/phobos/std_traits.html#ReturnType http://dlang.org/phobos/std_traits.html#ParameterTypeTuple

These are interesting and can be useful, but allMembers returns strings and not functions, so I can't apply ReturnType.

On 6/19/15 10:01 AM, Baz wrote:
> On Friday, 19 June 2015 at 13:52:54 UTC, Quentin Ladeveze wrote:
>> On Friday, 19 June 2015 at 13:38:45 UTC, Steven Schveighoffer wrote:
>>>
>>> Does this work for you, or is there a further expectation?
>>>
>>> auto asTuple() { return Tuple!(int, "a", ...)(a, b, stringValue);}
>>>
>>> -Steve
>>
>> In fact, I was trying to use traits to create the tuple automatically
>> and being able to add or remove methods to the struct without breaking
>> the asTuple method.
>> I used allMembers for the name of the methods, but I didn't found
>> anything for their return types or their values.
>>
>> Thank you.
>
> when the return type is defined inside the function it's called a
> 'Voldemort type',
> see http://www.drdobbs.com/cpp/voldemort-types-in-d/232901591?pgno=2

Actually, this isn't a voldemort type, because the type can be named outside the function.

-Steve

On 6/19/15 10:13 AM, Quentin Ladeveze wrote:
> On Friday, 19 June 2015 at 14:04:05 UTC, Daniel Kozák wrote:
>>
>> On Fri, 19 Jun 2015 13:52:52 +0000
>> Quentin Ladeveze via Digitalmars-d-learn
>> <digitalmars-d-learn@puremagic.com> wrote:
>>
>>> On Friday, 19 June 2015 at 13:38:45 UTC, Steven Schveighoffer wrote:
>>> >
>>> > Does this work for you, or is there a further expectation?
>>> >
>>> > auto asTuple() { return Tuple!(int, "a", ...)(a, b, > stringValue);}
>>> >
>>> > -Steve
>>>
>>> In fact, I was trying to use traits to create the tuple
>>> automatically and being able to add or remove methods to the
>>> struct without breaking the asTuple method.
>>> I used allMembers for the name of the methods, but I didn't found
>>> anything for their return types or their values.
>>>
>>> Thank you.
>> http://dlang.org/phobos/std_traits.html#ReturnType
>> http://dlang.org/phobos/std_traits.html#ParameterTypeTuple
>
> These are interesting and can be useful, but allMembers returns strings
> and not functions, so I can't apply ReturnType.

It's a *compile time* string. D is able to do some amazing things with this :)

// assuming 'a' is the first member
mixin("alias aReturnType = ReturnType!(Example." ~ __traits(allMembers, Example)[0] ~ ");");
static assert(is(aReturnType == int));

Using foreach over allMembers, you can construct a perfect return tuple using introspection and mixin.

-Steve

On Fri, 19 Jun 2015 13:27:13 +0000, Quentin Ladeveze wrote:
> 
> Is there any way to have a asTuple method in this struct that would returns something like :
> 
> Tuple!(int, "a", float, "b", string, "c")
> 
> and that will contain the values of the methods of the struct ?
> 
> Thanks.

You'll want to work your way through this example carefully as it's
basically template-based functional programming, but I think does what
you want:
 http://dpaste.dzfl.pl/b048ea3adb93

On Friday, 19 June 2015 at 14:13:46 UTC, Quentin Ladeveze wrote:
>> [..]
> These are interesting and can be useful, but allMembers returns strings and not functions, so I can't apply ReturnType.

Here's my solution:
http://dpaste.dzfl.pl/c69de3c16d75

On Friday, 19 June 2015 at 14:42:59 UTC, Steven Schveighoffer wrote:
> On 6/19/15 10:13 AM, Quentin Ladeveze wrote:
>> On Friday, 19 June 2015 at 14:04:05 UTC, Daniel Kozák wrote:
>>>
>>> On Fri, 19 Jun 2015 13:52:52 +0000
>>> Quentin Ladeveze via Digitalmars-d-learn
>>> <digitalmars-d-learn@puremagic.com> wrote:
>>>
>>>> On Friday, 19 June 2015 at 13:38:45 UTC, Steven Schveighoffer wrote:
>>>> >
>>>> > Does this work for you, or is there a further expectation?
>>>> >
>>>> > auto asTuple() { return Tuple!(int, "a", ...)(a, b, > stringValue);}
>>>> >
>>>> > -Steve
>>>>
>>>> In fact, I was trying to use traits to create the tuple
>>>> automatically and being able to add or remove methods to the
>>>> struct without breaking the asTuple method.
>>>> I used allMembers for the name of the methods, but I didn't found
>>>> anything for their return types or their values.
>>>>
>>>> Thank you.
>>> http://dlang.org/phobos/std_traits.html#ReturnType
>>> http://dlang.org/phobos/std_traits.html#ParameterTypeTuple
>>
>> These are interesting and can be useful, but allMembers returns strings
>> and not functions, so I can't apply ReturnType.
>
> It's a *compile time* string. D is able to do some amazing things with this :)
>
> // assuming 'a' is the first member
> mixin("alias aReturnType = ReturnType!(Example." ~ __traits(allMembers, Example)[0] ~ ");");
> static assert(is(aReturnType == int));
>
> Using foreach over allMembers, you can construct a perfect return tuple using introspection and mixin.
>
> -Steve

I would never have thought about mixins, this is amazing ! But thinking at compile time still is a little difficult for me, and now I don't understand how you can construct your tuple. I've been trying to create a string, by iterating on allMembers and concatenating the result of my functions in a string. But of course, I cannot use this string at compile time.

Now I know there is a way t do it, but my brain just can't figure it out.

Can you help me ?

On Friday, 19 June 2015 at 15:36:54 UTC, Justin Whear wrote:
> On Fri, 19 Jun 2015 13:27:13 +0000, Quentin Ladeveze wrote:
>> 
>> Is there any way to have a asTuple method in this struct that would returns something like :
>> 
>> Tuple!(int, "a", float, "b", string, "c")
>> 
>> and that will contain the values of the methods of the struct ?
>> 
>> Thanks.
>
> You'll want to work your way through this example carefully as it's
> basically template-based functional programming, but I think does what
> you want:
>  http://dpaste.dzfl.pl/b048ea3adb93

This is interesting, thank you very much ! I will try to figure out how it works now

On Friday, 19 June 2015 at 15:47:09 UTC, ZombineDev wrote:
> On Friday, 19 June 2015 at 14:13:46 UTC, Quentin Ladeveze wrote:
>>> [..]
>> These are interesting and can be useful, but allMembers returns strings and not functions, so I can't apply ReturnType.
>
> Here's my solution:
> http://dpaste.dzfl.pl/c69de3c16d75

Thank you very much, this solution is interesting too.

On 6/19/15 12:09 PM, Quentin Ladeveze wrote:
> On Friday, 19 June 2015 at 14:42:59 UTC, Steven Schveighoffer wrote:
>> On 6/19/15 10:13 AM, Quentin Ladeveze wrote:
>>> On Friday, 19 June 2015 at 14:04:05 UTC, Daniel Kozák wrote:
>>>>
>>>> On Fri, 19 Jun 2015 13:52:52 +0000
>>>> Quentin Ladeveze via Digitalmars-d-learn
>>>> <digitalmars-d-learn@puremagic.com> wrote:
>>>>
>>>>> On Friday, 19 June 2015 at 13:38:45 UTC, Steven Schveighoffer wrote:
>>>>> >
>>>>> > Does this work for you, or is there a further expectation?
>>>>> >
>>>>> > auto asTuple() { return Tuple!(int, "a", ...)(a, b, > >
>>>>> stringValue);}
>>>>> >
>>>>> > -Steve
>>>>>
>>>>> In fact, I was trying to use traits to create the tuple
>>>>> automatically and being able to add or remove methods to the
>>>>> struct without breaking the asTuple method.
>>>>> I used allMembers for the name of the methods, but I didn't found
>>>>> anything for their return types or their values.
>>>>>
>>>>> Thank you.
>>>> http://dlang.org/phobos/std_traits.html#ReturnType
>>>> http://dlang.org/phobos/std_traits.html#ParameterTypeTuple
>>>
>>> These are interesting and can be useful, but allMembers returns strings
>>> and not functions, so I can't apply ReturnType.
>>
>> It's a *compile time* string. D is able to do some amazing things with
>> this :)
>>
>> // assuming 'a' is the first member
>> mixin("alias aReturnType = ReturnType!(Example." ~
>> __traits(allMembers, Example)[0] ~ ");");
>> static assert(is(aReturnType == int));
>>
>> Using foreach over allMembers, you can construct a perfect return
>> tuple using introspection and mixin.
>>
>> -Steve
>
> I would never have thought about mixins, this is amazing ! But thinking
> at compile time still is a little difficult for me, and now I don't
> understand how you can construct your tuple. I've been trying to create
> a string, by iterating on allMembers and concatenating the result of my
> functions in a string. But of course, I cannot use this string at
> compile time.
>
> Now I know there is a way t do it, but my brain just can't figure it out.
>
> Can you help me ?

The string must stay compile time. This means it must be calculated:

1. in a mixin statement

Example is what I wrote earlier.

2. as an initializer to an immutable, enum, or non-local variable

enum x = "Blah." ~ __traits(allMembers, Blah)[0]; // x is compile-time

3. inside a CTFE function. A CTFE function is just a normal runtime function with restrictions (see http://dlang.org/function.html#interpretation). But you must *call* it from a context like 1 or 2:

string foo(string a, string b) { return a ~ b; } // foo is CTFEable

auto x1 = foo("a", "b"); // x1 is a runtime string, foo is called at runtime
enum x2 = foo("a", "b"); // x2 is a compile-time string, foo is executed at compile time (it is not called during execution of your program
mixin("int " ~ x1 ~ ";"); // error, can't use runtime string x1
mixin("int " ~ x2 ~ ";"); // ok, declares int ab;
mixin("int " ~ foo("c", "d") ~ ";"); // ok, declares int ab;

Keep your code all executing at compile time, and you can use your strings to write your code for you!

-Steve