Passing function parameters by name

[Bill Baxter]

Leandro Lucarella wrote:
> Bill Baxter, el  6 de diciembre a las 16:58 me escribiste:
>> Janice Caron wrote:
>>> On Dec 5, 2007 1:48 PM, renoX <renosky at free.fr> wrote:
>>>> I could ask the opposite question: why should we restrict the API to the function and 
>>>> object name instead of using the full data that we have?
>>> I often write constructor functions which look something like this
>>>    this(int x_, int y_, int z_)
>>>    {
>>>        x = x_;
>>>        y = y_;
>>>        z = z_;
>>>    }
>>> If parameter names were part of the API, then anyone calling my code
>>> would have to refer to those constructor parameters as x_, y_ and z_,
>>> complete with trailing underscores
>>> Of course, I could go back and change all my code to
>>>    this(int x, int y, int z)
>>>    {
>>>        this.x = x;
>>>        this.y = y;
>>>        this.z = z;
>>>    }
>>> but that would be a lot of code to change, and it might break calling code!
>> That's why any named parameter proposal is going to have to flag the named parameters 
>> somehow.  Non-flagged parameters will continue to behave as always.
> 
> I don't see what's the big problem with named parameters being part of the
> API (when, by convention, you are told so). This is widely used on Python
> and works just great and it's damn useful.

In Python you cannot overload functions based on argument types. 
Keyword arguments help to fill the void that leaves.  So C++ and D don't 
need keyword args quite as badly as Python.

Also a D implementation probably would lack many of the features of 
Python's keyword args.  I doubt you would be able to do things like 
passing an AA as a set of keyword arguments.

I think in the end this is a feature that would be nice but
A) probably needs to be designed as part of the language from the 
beginning.
B) needs to be a pet peeve of the person writing the compiler.

--bb