DIP 1030--Named Arguments--Community Review Round 1 Discussion

[Sasha]

On Wednesday, 12 February 2020 at 21:11:12 UTC, Jonathan Marler 
wrote:
> You could use variables to make it look nicer at the call-side, 
> but the downside is there's no guarantee that those variable 
> names have any relation to the names of the parameters. For 
> example, this would still compile:
>
> makeWindow(x, width, y, height);
>
> This problem can't happen with named arguments.  Named 
> arguments also saves you if the function arguments change 
> names/meaning, i.e.
>
> ORIGINAL: void makeWindow(int x, int y, int width, int height)
> MODIFIED: void makeWindow(int left, int top, int right, int 
> bottom);
>
> The version that doesn't use named arguments will still compile 
> and run:
>
> makeWindow(x, y, width, height);
>
> But named arguments would catch the problem at compile-time:
>
> makeWindow(x: 67, y: 98, width: 100, height: 100); // error no 
> argument named 'x', 'y', 'width', 'height'

OK, now let's see a problem with named arguments, imagine this:

makeWindow(x, y, width, height);

You can call this function like:

makeWindow(x: 67, y: 98, width: 100, height: 100); // Name 
Arguments
makeWindow(67, 98, 100, 100); // Constants
makeWindow(x, y, width, height); // Variables

So far so good, but later someone decides to rename some 
parameters to:

makeWindow(posx, posy, width, height); // Note: x => posx and y 
=> posy

makeWindow(x: 67, y: 98, width: 100, height: 100); // Ops not 
working anymore!
makeWindow(67, 98, 100, 100); // Constants still works
makeWindow(x, y, width, height); // Variables Still works

What I mean is that we need to balance this better, you showed a 
defect without Named Arguments and I'm showing a problem with.

But one thing that called my attention is that for what I see C++ 
doesn't has this feature, and proposes were rejected because the 
problems that would be created with this feature.

Sasha.