Clojure 猫追加 nil 行为

Question

我正在使用 funcool/cats，使用以下代码附加幺半群：

(m/mappend (maybe/just [1 2 3])
             nil
             (maybe/just [4 5 6])
             (maybe/nothing)) ;;=> #<Just [1 2 3 4 5 6]>

将 nil 视为 maybe/nothing 的理由是什么？

注：版本为[funcool/cats "1.2.1"]

Answer 1

从commit log来看，好像是

just for (sic) avoid accidental null pointer exceptions

Given the fact that nil is both a value and a type, we have extended the nil type to be equivalent to Maybe monad’s Nothing.

Clojure cats append nil behaviour