在fp里，函数没有副作用，变量都是不易变的。而在OOP中，可变状态和副作用都十分常见，甚至是被鼓励的。

In FP, functions have no side effects and variables are immutable, while in OOP, mutable state and side effects are common, even encouraged.

youdao

键并不限制为整数；它可以是任何不易变的数据类型，包括 integer、float、tuple 或 string。

The key isn't restricted to being an integer; it can be any nonmutable data type, including an integer, float, tuple, or string.

youdao

Scala通过Actors库来支持这种模式，但是它同时允许mutable(易变的)和immutable(不易变的)变量。

Scala supports this model with its Actors library, but it allows for both mutable and immutable variables.

youdao