Re: check instance of nested variadic template

[Gianni Pisetta via Digitalmars-d-learn]

When i have time i will test it with ldc and see if the result is 
the same, then it will probably be a front-end bug and i will 
report it as an issue.

Re: check instance of nested variadic template

[Gianni Pisetta via Digitalmars-d-learn]

On Friday, 4 November 2016 at 17:37:10 UTC, Basile B. wrote:


Hello, I'm not sure that's exactly what you want but check this:


template A(As...) {
template B(Bs...) {
}
}

alias BI = A!(1,2).B!(3,4,5);

import std.traits;

template NestedTemplateArgsOf(alias T)
{
alias NestedTemplateArgsOf = 
TemplateArgsOf!(__traits(parent, T));

}

alias Bs = TemplateArgsOf!BI;
alias As = NestedTemplateArgsOf!BI;


static if (is(typeof(BI) == typeof(A!As.B!Bs)))
{
pragma(msg, "for the win");
}


The missing key was NestedTemplateArgsOf. With it you can solve 
the problem.


Well, kind of. But i think i can make it with what i got from 
your example, so thanks.
Another thing that I encountered and while messing with your code 
is that __traits( parent, T ) does not work as expected when you 
have structs instead of template. I think because something like


struct A(As...) {}

is downgraded to

template A(As...) {
  struct A {}
}

when i use __traits( parent, A!(1,2) ) i get in return A!(1,2), 
looping around the same symbol.

When you compile this

struct A(As...) {}

import std.conv;

pragma( msg, "The parent symbol is the same? " ~ to!string( 
__traits( isSame, A!(1,2), __traits( parent, A!(1,2) ) ) ) );


void main() {}

you get a really interesting result:

The parent symbol is the same? true

Gianni Pisetta

check instance of nested variadic template

[Gianni Pisetta via Digitalmars-d-learn]

Hi all,
I am having issues finding a solution for this, i want to check 
if an alias is an istance of a variadic template nested in 
another variadic template.

Here is an example:

template A(As...) {
template B(Bs...) {
}
}

alias BI = A!(1,2).B!(3,4,5);

Now i want to test if BI is an istance of A.B, but i can't do 
something like this:


static if ( is( BI == A!As.B!Bs, As..., Bs... ) ) {
// Do Something
}

there is some sort of workaround?

Thanks,
Gianni

Re: test if the alias of a template is a literal

[Gianni Pisetta via Digitalmars-d-learn]

On Friday, 28 October 2016 at 03:33:33 UTC, Basile B. wrote:

Hello, I think the correct isStringLiteral would be:

import
std.meta;

template isStringLiteral(alias V)
{
enum isCompileTime = is(typeof((){enum a = V;}));
enum isString = is(typeof(V) == string);
enum isStringLiteral = isCompileTime && isString;
}



It works, Thanks. Also, i don't think in my case there is the 
need for a variant for types( aka isStringLiteral(V) without 
alias) because it's an error to pass a type to Optimize in first 
place. But for a general purpouse library, maybe a template 
isLiteral(alias V) that only checks if it is a literal without 
the type checking, would have more sense to have also 
isLiteral(V) for types that returns always false.


Gianni Pisetta

Re: test if the alias of a template is a literal

[Gianni Pisetta via Digitalmars-d-learn]

On Thursday, 27 October 2016 at 14:34:38 UTC, TheFlyingFiddle 
wrote:
On Thursday, 27 October 2016 at 14:04:23 UTC, Gianni Pisetta 
wrote:

Hi all,
but at the moment isStringLiteral will return true even with 
variables of type string. So i searched for a metod to check 
if an alias is a literal value, but found nothing. Anyone have 
any clue on how can be done?


Thanks,
Gianni Pisetta


Not really understanding your problem. Could you include an 
example use that is problematic?


Yea, sorry I missed that.
A really stupid example would be

string var;

alias Sequence = Optimize!( "The", " ", "value", " ", "of", " ", 
"var is ", var );


static assert( is( Sequence == AliasSeq!( "The value of var is ", 
var ) ) );


writeln( Sequence );

given that you include the code snippet in the first post.

Thanks, Gianni

test if the alias of a template is a literal

[Gianni Pisetta via Digitalmars-d-learn]

Hi all,
I have an AliasSeq composed of literal strings, variables and 
delegates. I want to build a template Optimize that will return 
an AliasSeq that have all adjacent literals concatenated into 
one. So i writed something like this:


template isStringLiteral(alias V) {
enum bool isStringLiteral = ( is( typeof( V ) == string ) );
}

template Optimize(Os...) {
static if ( Os.length < 2 )
alias Optimize = Os;
else {
alias Optimized = Optimize!(Os[1..$]);

static if ( isStringLiteral!(Os[0]) && 
isStringLiteral!(Optimized[0]) ) {

enum string First = Os[0] ~ Optimized[0];
alias Rest = Optimized[1..$];
}
else {
alias First = AliasSeq!(Os[0]);
alias Rest = Optimized;
}
alias Optimize = AliasSeq!(First, Rest);
}
}

but at the moment isStringLiteral will return true even with 
variables of type string. So i searched for a metod to check if 
an alias is a literal value, but found nothing. Anyone have any 
clue on how can be done?


Thanks,
Gianni Pisetta