概念

1.

Purely functional is a term(术语) in computing used to describe algorithms, data structures or programming languages that exclude(排除/排斥) destructive(有破坏性的) modifications (updates). According to this restriction(限制/限定), variables are used in a mathematical sense, with identifiers referring to immutable(恒定不变的), persistent(持续性/一贯) values.

2.

In computer science and computer programming, a type system is said to feature strong typing when it specifies one or more restrictions on how operations involving values of different data types can be intermixed(混合). The opposite(相反) of strong typing is weak typing.

3.

A programming language is said to use static typing when type checking is performed during compile-time as opposed(相对/反对) to run-time.

4. ()

In computer science, an evaluation strategy is a set of (usually deterministic(确定性)) rules for evaluating expressions in a programming language. Emphasis(强调/重点) is typically placed on functions or operators: an evaluation strategy defines when and in what order the arguments to a function are evaluated, when they are substituted into(代入) the function, and what form that substitution takes. The lambda calculus, a formal system for the study of functions, has often been used to model evaluation strategies, where they are usually called reduction strategies. Evaluation strategies divide into two basic groups, strict and non-strict, based on how arguments to a function are handled. A language may combine several evaluation strategies; for example, C++ combines call-by-value with call-by-reference. Most languages that are predominantly(主要) strict use some form of non-strict evaluation for boolean expressions and if-statements.