• Atila Neves (35/35) May 10 2017 http://code.dlang.org/packages/concepts
• =?UTF-8?B?THXDrXM=?= Marques (2/5) May 10 2017 Awesome!
• Juanjo Alvarez (3/12) May 11 2017 Niiiiice, I love constraints but there error messages aren't the

Atila Neves <atila.neves gmail.com> writes:

http://code.dlang.org/packages/concepts

concepts is a dub package and library that allows one to declare 
that a struct conforms to a "compile-time interface" such as 
`isInputRange`. The difference between this and a simple `static 
assert(isInputRange!MyType)` is that when the static assert fails 
you have no idea why not and half of the time it's because of a 
typo (e.g. `popFrnt`). With concepts you get an error message 
from the compiler, and you can still use your concepts in 
template constraints.

It also has its own version of `isInputRange` et al that are 
drop-in replacements for the ones in Phobos, but you get compiler 
error messages instead of nothing.

The new addition is ` implements`:

interface IFoo {
     int foo(int i, string s)  safe;
     double lefoo(string s)  safe;
}

 implements!(Foo, IFoo)
struct Foo {
     int foo(int i, string s)  safe { return 0; }
     double lefoo(string s)  safe { return 0; }
}

// doesn't compile: Foo doesn't "implement" IFoo
/*
 implements!(Oops, IFoo)
struct Oops {}
*/

// also doesn't compile because foo is  system:
/*
 implements!(Nearly, IFoo)
struct Nearly {
     int foo(int i, string s)  system { return 0; }
     double lefoo(string s)  safe { return 0; }
}
*/

=?UTF-8?B?THXDrXM=?= Marques <luis luismarques.eu> writes:

On Wednesday, 10 May 2017 at 10:53:59 UTC, Atila Neves wrote:
 concepts is a dub package and library that allows one to 
 declare that a struct conforms to a "compile-time interface" 
 such as `isInputRange`.

Awesome!

Juanjo Alvarez <gorthol protonmail.com> writes:

On Wednesday, 10 May 2017 at 10:53:59 UTC, Atila Neves wrote:
 http://code.dlang.org/packages/concepts

 concepts is a dub package and library that allows one to 
 declare that a struct conforms to a "compile-time interface" 
 such as `isInputRange`. The difference between this and a 
 simple `static assert(isInputRange!MyType)` is that when the 
 static assert fails you have no idea why not and half of the 
 time it's because of a typo (e.g. `popFrnt`). With concepts you 
 get an error message from the compiler, and you can still use 
 your concepts in template constraints.

Niiiiice, I love constraints but there error messages aren't the 
best.