Fix bugs in gen/fmap documentation

[schmudde]

The documentation for clojure.test.check.generators/fmap will throw an error when run.

gen/fmap has a signature of [f gen]. The generators in spec.adoc are being cast to function names in the example calls to gen/fmap (e.g. (gen/string-alphanumeric)). They should be evaluated as a generator (e.g. gen/string-alphanumeric).

The current evaluation result is an Execution error: class clojure.test.check.generators.Generator cannot be cast to class clojure.lang.IFn. The proposed changes allow for proper execution.

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[puredanger]

fmap in these examples is not clojure.test.check.generators/fmap, it's clojure.spec.gen.alpha/fmap. The spec generators wrap and modify the test.check generator functions to take generator thunks, not generators. So this code is correct as written. The changes you suggest would be correct if using the c.t.c.g/fmap directly (but as seen in the guide it's (require '[clojure.spec.gen.alpha :as gen])).

[schmudde]

I see. Hence the big yellow box in this section that says:

The last option [3. Use test.check or other test.check compatible libraries] requires a runtime dependency on test.check so the first two options [1. Let spec create a generator based on a predicate/spec 2. Create your own generator from the tools in clojure.spec.gen.alpha] are strongly preferred over using test.check directly.