Generate random number in interval in PostScript

Question

I am struggling to find a way to generate a random number within a given interval in PostScript.

Basically PostScript has three functions to help you generate (pseudo-)random numbers. Those are rand, srand and rrand.

The later two are for passing a seed to the number generator to be able to reproduce specific results. At least that´s what I understood they are for. Anyway they don´t seem suitable for my case.

So rand seems to be the only function I can use to generate a random number, but...

rand returns a random integer in the range 0 to 2³¹ − 1

(From the PostScript Language Reference, page 637 (651 in the PDF))

This is far beyond the the interval I´m looking for. I am more interested in values up to small thousands, maybe 10.000 or something like that and small float values, up to 100, all with the lower limit of 0.

I thought I could just narrow my numbers down by simple divisions and extracting the root but that tends to give me unusable small values in quite a lot cases. I am wondering if there are robust ways to either shrink a large number down to what I need or, I´d prefer that, only generate numbers in the desired interval.

Besides: while-loops are not possible in PostScript, otherwise I´d have written a function to generate numbers until they fit in my interval.

Any hints on what to look for breaking numbers down into my interval?

Answer 1

Just use the modulo operator to get it down to the size you want:

GS>rand 100 mod stack
7