Clojure Learning 05: Predicate functions

A predicate function is a judgment, a function that returns a bool value.

clojure (Lisp habit): For functions that Judge functions, there is a function name followed by a "? No. So as long as you see the name of the function with a question mark in the back, you know it must be a judgment function.

1, instance?  checks if the value is of a type

user=> (instance? String "Hello")
true

2, fn?  Determines whether a parameter represents a function

user=> (Def a)
# ' user/a
user=> (fn? a)
False
User=> (fn? filter)
True

3, The predicate for the test number has a

even even?

odd odd?

negative neg?

positive pos?

0 Zero?

Clojure Learning 05: Predicate functions