Is it not possible to generate a pseudo random number via a function in a functional programming language?

Question

Because a function in such a language needs to produce the same output for a given or null input? Otherwise, can a long pseudorandom sequence be used and the function be called with a sequential input each time?

Answer 1

Happy testing Mane SoloTest

Answer 2

Mane SoloTest helpful in what way?

Answer 3

“We get the same answer twice because the underlying function [random] that’s deciding the values returned is pure; the type doesn’t permit the performance of any effects to get spooky action.”

Excerpt From
Haskell Programming from first principles
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So it seems like the pseudorandom number generator is pure. I’m not sure how though.