what is it you want to generate exactly?

are you trying to generate a 2-value vector containing ints that can be used with apply as the args for sbtrct?

generators generate values, so by providing a spec for each of your input args and for your return value, you've already provided generators (because spec provides a built-in generator for the int? predicate)

@U053032QC I want to generate a sequence of args/ret values such that they satisfy relation defined in :fn spec

ah, ok:

(s/exercise-fn `sbtrct)

that'll generate a bunch of input values for a and b (using the generators provided by their specs, i.e. int?), put them into your function, and return you a sequence of those input pairs with the calculated output

if your function doesn't match your :fn spec, it'll blow up

if you want to do a larger number of tests of your function, you can do generative testing using clojure.spec.test.alpha/check

so

(stest/check `sbtrct`)

that'll generate 1000 different inputs and check all the outputs for conformance with your :ret spec and :fn predicate

neat, huh?

> if you want to do a larger number of tests of your function.. that’s exactly what I need, exercise-fn doesn’t seem to be able to generate huge sequences 🙂

you can do

(s/exercise-fn `sbtrct 100000)

oh no, looks like that blows up

yeah I’m getting integer overflow

doesn't blow up so long as you don't print it

oooooh, damn

might just be lazy though

yeah it's lazy

so there are numbers in there that blow up

hm, what can be done about this?

do you need the ints to be very large?

no, just a lot of them

if not, you could try

(s/def ::small-int (s/int-in 0 1000000))
(s/fdef sb
  :args (s/cat :a ::small-int :b ::small-int)
  :ret int?
  :fn #(= (:ret %) (- (-> % :args :a) (-> % :args :b))))

that's specifying a range that the ints can be in, so you won't get huge numbers generated

Should I use with-gen if I don’t want to modify the original spec?

with-gen is for when you need to create your own generator because the existing ones can't capture your set of values

i guess you'll have to look into what's actually causing the error

that approach above works for me though, with s/int-in as the spec for the inputs to your function

i used a different name for my function though so don't just copy/paste

works for me as well, thanks!

no worries, docs are often a bit sparse around spec, but it is alpha, so /shrug

I ended up with (s/int-in Integer/MIN_VALUE Integer/MAX_VALUE)