[fpc-pascal] named parameter

[Bernd Oppolzer]

IMO, it's not about named parameters;
furthermore, it is not about readability, but this IMO
is a maintenance issue.

Think about a procedure that has two parameters and a lot of callers
and you want to add a third one.

it would be nice if you could specify a default value for the new
third parameter and don't have to change all the callers that use
only two.

So IMO a sensible extension to the Pascal syntax could be:

if there is a initialization on the procedure declaration, the parameter
is optional.

Example:

procecure P (x : integer; y : boolean; c: char := ' ');

the first two parameters are mandatory, the third is optional.
Calls to P with 2 and 3 parameters are both valid.

Another extension would be:

specify the formal parameter's name on call, that is:

P (y := true, c := '*', x := 25);

which allows for a different sequence of arguments on the procedure call

but this is a different topic and should be discussed seperate from the
default issue.

I guess, that all this will be limited to byvalue parameters ... not for
var parameters ...

Kind regards

Bernd


Am 27.05.2017 um 08:17 schrieb Mr Bee via fpc-pascal:
> Hi,
>
> As Pascal mostly well known as a safe, easy to read, and elegant 
> language, don't you think Pascal needs named parameter? I mean for ALL 
> kind of parameters, not just for Variants. When you have a function 
> with many parameters having default values, you know that named 
> parameter is desirable. For example:
>
> function f(p1: string = ''; p2: integer = 0; p3: boolean = false);
>
> But you only need to supply the third parameter, you still must supply 
> the first and second ones with appropriate default values, like this:
>
> f('', 0, true);
>
> while with named parameter, you can do this:
>
> f(p3 := true);
>
> I believe it would raise Pascal's code readability. I know it has been 
> discussed before. I know somehow the parser had been able to read such 
> syntax. So, why don't we have the option to enable it for people who 
> want it? Kinda a syntax switch mode.
>
> What do you think? :)
>
> -- 
>
> Regards,
>
>
> –Mr Bee
>
>
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