Re: SRFI-27, deterministic random generator for floats

[Jeronimo Pellegrini]

On 2023-09-28 20:56, Zelphir Kaltstahl wrote:
> Hello Guile Users!

Hello!

> I am trying to deterministically generate random floats using SRFI-27 
> and I stumbled upon something weird:
>
> ~~~~
> (use-modules (srfi srfi-27))
>
> (define random-source (make-random-source))
> (define random-state (random-source-pseudo-randomize! random-source 0 
> 12345))
> (define random-float-gen (random-source-make-reals random-state))

random-source-make-reals does not accept a random-state, but a 
random-source (which has an internal random-state, which you already 
randomized with random-source-pseudo-randomize!)

That's why Guile is complaining about a wrong type of argument -- a 
random-state struct was passed, but a random-source was expected.

(By the way, my interpretation of the SRFI is that 
random-source-pseudo-randomize! changes the
internal state of the source passed to it, and it doesn't even need to 
return anything - Guile
seems to do it as a convenience)


> I do not understand, what I am doing wrong, since the same seems to 
> work for integers:

I do (see below). :)

> ~~~~
> (use-modules (srfi srfi-27))
>
> (define random-source (make-random-source))
> (define random-state (random-source-pseudo-randomize! random-source 0 
> 12345))
> (define random-integer-gen (random-source-make-integers random-source))
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

It works because you got it right this time (random-source, not 
random-state).

> What do I need to do, to get a deterministic generator like I have for 
> integers?

(define random-float-gen (random-source-make-reals random-source))  ;; 
<- source, not state

Does that fix it?

J.