structural-typing.api.predicates

Functions used to construct predicates that explain themselves, plus some frequently useful predicates of that sort.

Much of this is gathered into the catchall structural-typing.types namespace.

exactly

(exactly x)

Produce a predicate that’s true iff the value it’s applied to is = to x.

( (exactly 5) 4) => false (type! :V5 {:version (exactly 5)})

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explain-with

(explain-with explainer predicate)

After the predicate fails, the failure will need to be explained. Arrange for the explainer function to be called with the oopsie that results from the failure.

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member

(member coll)

Produce a predicate that’s false when applied to a value not a member of coll. The explainer associated with member prints those colls.

  ( (member [2 3 5 7]) 4) => false
  (type! :small-primes {:n (member [2 3 5 7])})
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required-key

False iff a key/path does not exist or has value nil. This is the only predicate that is not considered optional.

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should-be

(should-be format-string expected)
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show-as

(show-as name predicate)

Associate the given name string with the predicate for use when predicate failures are explained.

  (->> (partial >= 3) (show-as "less than 3"))
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