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September 08, 2020 Named parameters in function call | ||||
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I can’t remember, do Ada or Modula2 have something like myfunc( x => 100, y => 200, color => blue ) [1] which has named parameters that can be passed in any order. Does D have anything like this? If not, would anyone support a development like the above [1] ? If D does not have this, I am wondering about how to write such a thing but the cure might very very easily be worse than the disease. I have little clue here. I have seen a hack for C (written by RevK) that involves assignments to fields in a struct and the struct is then passed to a function. Something like myfunc( { field2: 20, field1: 10, fieldstr : "a string" } ) [2] and preprocessor trickery was used to get rid of the unsightly { } by making a macro call to a wrapper macro that takes variadic ... arguments. |
September 08, 2020 Re: Named parameters in function call | ||||
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Posted in reply to Cecil Ward | On Tuesday, 8 September 2020 at 07:43:05 UTC, Cecil Ward wrote: > I can’t remember, do Ada or Modula2 have something like > myfunc( x => 100, y => 200, color => blue ) [1] > which has named parameters that can be passed in any order. > > [...] I hope we have it this year or next year, as we have this DIP https://www.github.com/dlang/DIPs/tree/master/DIPs%2FDIP1030.md Kind regards Andre |
September 08, 2020 Re: Named parameters in function call | ||||
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Posted in reply to Andre Pany | On Tuesday, 8 September 2020 at 09:40:11 UTC, Andre Pany wrote:
> On Tuesday, 8 September 2020 at 07:43:05 UTC, Cecil Ward wrote:
>> I can’t remember, do Ada or Modula2 have something like
>> myfunc( x => 100, y => 200, color => blue ) [1]
>> which has named parameters that can be passed in any order.
>>
>> [...]
>
> I hope we have it this year or next year, as we have this DIP
> https://www.github.com/dlang/DIPs/tree/master/DIPs%2FDIP1030.md
>
> Kind regards
> Andre
I wonder if there is any way in which we could combine this with strong typing of some sort (how?) to detect errors such as
int xcoord;
int ycoord;
myfunc( x : ycoord, y : xcoord, color : blue ) [3]
where the arguments are the wrong way around. Would have to change the types of the xcoord and ycoord variables somehow, something I have asked about earlier.
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September 09, 2020 Re: Named parameters in function call | ||||
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Posted in reply to Cecil Ward | On Tuesday, 8 September 2020 at 13:28:22 UTC, Cecil Ward wrote:
> int xcoord;
> int ycoord;
You can define your own types, of course:
struct xcoord { int x; alias x this; }
struct ycoord { int y; alias y this; }
void myfunc(xcoord x; ycoord y, color c) {}
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September 09, 2020 Re: Named parameters in function call | ||||
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Posted in reply to Cecil Ward | On Tuesday, 8 September 2020 at 13:28:22 UTC, Cecil Ward wrote:
>
> I wonder if there is any way in which we could combine this with strong typing of some sort (how?) to detect errors such as
> int xcoord;
> int ycoord;
>
> myfunc( x : ycoord, y : xcoord, color : blue ) [3]
>
> where the arguments are the wrong way around. Would have to change the types of the xcoord and ycoord variables somehow, something I have asked about earlier.
import std.typecons: Typedef;
alias XCoord = Typedef!(int, int.init, "XCoord");
alias YCoord = Typedef!(int, int.init, "YCoord");
auto myfunc(XCoord x, YCoord y) { ... }
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September 09, 2020 Re: Named parameters in function call | ||||
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Posted in reply to Paul Backus | On Wednesday, 9 September 2020 at 11:48:28 UTC, Paul Backus wrote:
> On Tuesday, 8 September 2020 at 13:28:22 UTC, Cecil Ward wrote:
>>
>> I wonder if there is any way in which we could combine this with strong typing of some sort (how?) to detect errors such as
>> int xcoord;
>> int ycoord;
>>
>> myfunc( x : ycoord, y : xcoord, color : blue ) [3]
>>
>> where the arguments are the wrong way around. Would have to change the types of the xcoord and ycoord variables somehow, something I have asked about earlier.
>
> import std.typecons: Typedef;
>
> alias XCoord = Typedef!(int, int.init, "XCoord");
> alias YCoord = Typedef!(int, int.init, "YCoord");
>
> auto myfunc(XCoord x, YCoord y) { ... }
Brilliant. Thank you Paul.
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