Re: SRFI-27, deterministic random generator for floats

[Zelphir Kaltstahl <zelphirkaltstahl@posteo.de>]

On 9/29/23 02:18, Jeronimo Pellegrini wrote:
> On 2023-09-28 20:56, Zelphir Kaltstahl wrote:
>> 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.

Ah, thank you Jeronimo!

I was under the impression that random-source-make-reals wants the random state >.<

This apparently work, thank you!

Regards,
Zelphir

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