What is the best way to spec a string that contains a floating point number? Using a regex or some other method?

Float/parseFloat comes to mind

So what would the spec look like? In particular, would I have to write a custom generator?

It might look like: (s/spec #(Double/parseDouble %) :gen (gen/fmap str (gen/double)))

Possibly using gen/double* with some constraints

@donaldball Cool, thanks! Unfortunately I'm in cljs-land, so I think I might have to go the regex path anyway

maybe js/parseFloat can help then @curlyfry

Right!

Just one more thing: When you make a spec like (s/def ::double-string #(Double/parseDouble %)) we rely on parseDouble throwing an exception rather than matching a certain predicate, right?

js/parseFloat is a bit too forgiving: (js/parseFloat "1.23abcdef") => 1.23

Ended up with:

(def decimal-regex #"-?\d+\.\d+")
(s/def ::double-string (s/spec (s/and string? #(re-matches decimal-regex %)) :gen #(gen/fmap str (gen/double))))

if you end up doing that a lot (specing via regex) you might want to check test.chuck for the gen part

especially test.chuck.generators/string-from-regex

I've thrown crazy regexes at it and it never failed me (so far)

@curlyfry not saying a nicer way doesn’t exist, but that way is straightforward and works well, and it’s the way i’d do it

@mpenet @joshjones Sweet, thanks guys!

@seancorfield I know that you answered it with I think a namespace and a function ( artObjects-id:response ) but when I used it in a sdef I did not work