feat: user-defined function that returns a vector instead of a single value

[guilhem-martin]

Hello,

I'd like to define a function like "prime number integer factorization".
Example: decomp(15) would return [3,5] ; decomp(61) would return [61].

As far as I understand, it's not possible for a user-defined function to return several values.
This issue is to suggest an evolution to support return multiple values, a list for instance.

Thanks.

[hanna-kn]

It is possible to return multiple values in i vector, but efficient implementation of factorization in a user-defined function would be difficult.

A function which returns all unique prime factors can be defined as follows.
Subfunction: process(if(\x%\p, 0, \p), \p, primes(\x/2))
Function: if(element(\1, 1)=0, \x, limits(\1, 1, sum(\p>0, 1, elements(\1))))

[guilhem-martin]

Many thanks for your help!

[hanna-kn]

I just realised that there is a much is easier way to define the prime factors function:
select(primes(\x),\x%\p=0,\p)

[hanna-kn]

Considering that the above function is much less efficient (noticeable for value > 100000) than using "to factors" (e.g. 15 to factors returns 3 × 5), and that you are not the first to ask for it, I will add a prime factors function (in code).