Ruud H.G. van Tol on Mon, 25 Dec 2023 20:09:49 +0100


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Re: reference parameters 


On 2023-12-25 19:34, Bill Allombert wrote:

On Mon, Dec 25, 2023 at 05:46:37PM +0100, Ruud H.G. van Tol wrote:

? ??listput
listput( list,x,{n}):

Not that this is a bug in the doc generator, the fixed version outputs
   listput(~list,x,{n}):

(~ is an unbreakable space in TeX).


    Sets the n-th element of the list list (which must be of type t_LIST)
equal to x. If n is omitted, or greater than the list length, appends x. The
function returns the inserted element.

    ? L = List();
    ? listput(~L, 1)
    %2 = 1
    ? listput(~L, 2)
    %3 = 2
    ? L
    %4 = List([1, 2])

Note the ~ L: this means that the function is called with a reference to L
and changes L in place.

Is that explicit reference notation still relevant?

Why not ?

We allow to omit the "~" for backward compatibility only.
This is mandatory for user-defined functions, because GP functions
are not prototyped.



OK, I presumed that (it would be safe to make) both
listput( ~L, ... ) and listput( L, ... )do exactly the same. IOW, I expect that without the "~" the function is also "called with a reference to L and changes L in place." -- Ruud