https://code.dlang.org/packages/kwargs

There have been many posts asking about keyword arguments for D a la Python. Usually I reply saying to just use the type system, but that has the incovenience of having to pass all 7 parameters before the optional 8th one you actually care about despite you being ok with the default values before that. std.process.execute is a particular thorn in my side since I usually only want to change `workDir`, but I digress. Behold:


--------------------------
import kwargs;

struct Foo { string value; }
struct Bar { string value; }
struct Baz { string value; }

size_t funImpl(in Foo foo, in Bar bar = Bar("lebar"), in Baz baz = Baz("lebaz")) {
    return foo.value.length + bar.value.length + baz.value.length;
}

alias fun = kwargify!funImpl;

fun(Foo()).should == 10;
fun(Bar("b"), Foo("fo")).should == 8;
fun(Bar("b"), Baz("ba"), Foo("foo")).should == 6;
------------------------------------------


The API for compile-time parameters isn't as nice, but seeing as how there's no way in D that I know of currently to reflect on those, this is what I managed to conjure up:


----------------------
struct Foo { int val; }
struct Bar { int val; }
struct Baz { int val; }

int[] funImpl(Foo foo, Bar bar, Baz baz)() {
    return [foo.val, bar.val, baz.val];
}

alias fun = kwargify!(funImpl, Required!Foo, Optional!(Bar(2)), Optional!(Baz(3)));

fun!(Foo(1)).should == [1, 2, 3];
fun!(Baz(9), Foo(7)).should == [7, 2, 9];
fun!(Baz(9), Bar(8), Foo(7)).should == [7, 8, 9];
----------------------

On Monday, 11 February 2019 at 17:03:36 UTC, Atila Neves wrote:
> import kwargs;
>
> struct Foo { string value; }
> struct Bar { string value; }
> struct Baz { string value; }
>
> size_t funImpl(in Foo foo, in Bar bar = Bar("lebar"), in Baz baz = Baz("lebaz")) {
>     return foo.value.length + bar.value.length + baz.value.length;
> }
>
> alias fun = kwargify!funImpl;
>
> fun(Foo()).should == 10;
> fun(Bar("b"), Foo("fo")).should == 8;
> fun(Bar("b"), Baz("ba"), Foo("foo")).should == 6;

So all arguments should have different types, right? Like here we have 3 strings wrapped in structs to distinguish them

On Monday, 11 February 2019 at 22:32:59 UTC, Vladimir Marchevsky wrote:
> On Monday, 11 February 2019 at 17:03:36 UTC, Atila Neves wrote:
>> import kwargs;
>>
>> struct Foo { string value; }
>> struct Bar { string value; }
>> struct Baz { string value; }
>>
>> size_t funImpl(in Foo foo, in Bar bar = Bar("lebar"), in Baz baz = Baz("lebaz")) {
>>     return foo.value.length + bar.value.length + baz.value.length;
>> }
>>
>> alias fun = kwargify!funImpl;
>>
>> fun(Foo()).should == 10;
>> fun(Bar("b"), Foo("fo")).should == 8;
>> fun(Bar("b"), Baz("ba"), Foo("foo")).should == 6;
>
> So all arguments should have different types, right? Like here we have 3 strings wrapped in structs to distinguish them

Yes, they all have to have different types.