DIP 1019--Named Arguments Lite--Final Review

[Nick Treleaven]

On Friday, 23 August 2019 at 19:57:05 UTC, a11e99z wrote:
> On Friday, 23 August 2019 at 19:48:59 UTC, Paul Backus wrote:
>> struct S { int a, b, c, d = 7; }
>> S w = { b:1, 3 };             // v.a = 0, v.b = 1, v.c = 3, 
>> v.d = 7
>
> unnamed arg after named is weird/error prone

It is fine, but only when the named argument has the same 
position as it would if it were unnamed.

void f(int a, b, c = 3, d = 4);
//Equivalent calls:
f(a: 1, 2, d: 5);
f(1, 2, 3, 5);

The purpose of writing `a: 1` is to describe the argument to the 
function at the call site, as programmers often won't look up the 
function signature just when reading code (e.g. on GitHub when 
they don't have the function open in their IDE).

Why not name b's argument too? Because that argument might be 
more obvious what it is. a might be passed a primitive literal 
but b might be passed a variable with the same name (or 
equivalent).