Getting Clojure

Why? Why? Why?

One issue with more complex specs is that it’s not always immediately clear why a particular value doesn’t match. For example, you might have to look at this expression for a while to see why valid? returns false:

(s/valid? ::book {:author :austen :title :emma})

To help you figure out why your spec isn’t matching, clojure.spec provides the explain function, which takes the same arguments as valid?. If the spec matches, explain will print a celebratory message, so that if you do this:

(s/explain n-gt-10 44)

you will see this:

Success!

Things are much more interesting if the spec doesn’t match. Do this:

(s/explain n-gt-10 1)

and you will see something like the following:

val: 4 fails predicate: (> % 10)

Thus we can use ...