`(s/gen ratio?)` throws exceptions

Wed, 08 May 2024 07:44:49 +0000

(s/gen ratio?) is implemented as (gen/such-that ratio? gen/ratio)

The problem is that about 10% of the time gen/ratio returns a whole number, which fails the ratio? predicate. If that happens 10 times in a row, gen/such-that throws an exception.

With a large enough sample size, (s/gen ratio?) reliably fails:

(dorun (gen/sample (s/gen ratio?) 10000000))

Execution error (ExceptionInfo) at clojure.test.check.generators/fn (generators.cljc:435).
Couldn't satisfy such-that predicate after 10 tries.

A quick fix is to increase the max-tries param for such-that:

(dorun (gen/sample (gen/such-that ratio? gen/ratio 100) 10000000))

=> nil

I do however also find it odd that (s/gen ratio?) always generates Ratios, but gen/ratio generates a mixture of ratios and integers. So perhaps a better fix would be to update gen/ratio to not generate integers?

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`(s/gen ratio?)` throws exceptions