Document pseudoness of random numbers

[uliska]

From a private discussion:

Random numbers in Scheme are only random if you initialize them to some "outside" value, e.g. the current time. This has been discussed just a few days ago: https://lists.gnu.org/archive/html/lilypond-user/2020-01/msg00496.html
Probably I should do so in the example because otherwise there's no practical use for the function.

I read but it did not help. I tried using this (set! random-state (random-state-from-platform)) in a couple of places. I got 61 or nothing

Well, it seems David's explanation was less useful than I thought.
I don't know what random-state-from-platform is, and I get an error from this.

The full documentation is at https://www.gnu.org/software/guile/docs/docs-1.8/guile-ref/Random.html#Random, and there you can find the explanation and an example for seed->random-state which David referenced.
You need to call that procedure with "something that isn't the same every time", for example with

\version "2.19.82"

#(set! *random-state*	
       (seed->random-state 
        (cdr (gettimeofday))))

#(display (random 100))

While this isn't really documented (shame on Guile!) it seems seed->random-state expects a string but auto-converts numbers to that. So it is possible to use one of the parts of the current time pair to seed the random state and get a different number in every run.

I think this should be described somewhere. Maybe a section with "various topics"?