用户定义的中缀运算符 [英] User-defined infix operator

问题描述

我知道Julia中的运算符只是标准函数，我可以通过以下方式使用它们 普通的前缀调用语法:

I know operators in Julia are just standard functions, and I can use them using the ordinary prefix call syntax:

julia> +(1, 2)
3

但是，它们在可以(通常是)的意义上也很特别 用作中缀运算符:

However, they are also special in the sense that they can be (and are usually) used as infix operators:

julia> 1+2
3

我可以定义自己的中缀运算符吗?如果是这样，怎么办?

例如:

julia> α(x, y) = x+y
α (generic function with 1 method)

julia> α(1, 2)
3 # as expected

julia> 1α2
# expected result: 3
ERROR: UndefVarError: α2 not defined
Stacktrace:
 [1] top-level scope at REPL[5]:1

julia> 1 α 2
# expected result: 3
ERROR: syntax: extra token "α" after end of expression
Stacktrace:
 [1] top-level scope at REPL[5]:0

推荐答案

正如您所说，运算符只是标准函数，您可以定义和定义 否则像其他任何功能一样进行操作.但是，朱莉娅的解析器是 配置为将某些符号集识别为中缀运算符；如果你 定义一个名称为这些符号之一的函数，它将被解析为 中缀运算符.

As you said, operators are just standard functions, which you can define and otherwise manipulate like any other function. However, Julia's parser is configured to recognize a certain set of symbols as infix operators; if you define a function whose name is one of these symbols, it will be parsed as an infix operator.

例如:

julia> ⊕(x, y) = x+y
⊕ (generic function with 1 method)

# standard prefix function call
julia> ⊕(1, 2)
3

# infix operator call
julia> 1⊕2
3

julia> 1 ⊕ 2
3

可以找到被识别为中缀运算符的符号列表(以及相关的优先级)在朱莉娅中 解析器源 代码.为了 大多数情况下，此列表是 unicode类别Sm 的子集(象征， 数学).

The list of symbols recognized as infix operators (and associated precedence) can be found in the Julia parser source code. For the most part, this list is a subset of unicode category Sm(Symbol, math).

目前，它包括例如:

• 以与+相同的优先级进行解析:

• parsed with the same precedence as +:

+ - ⊕ ⊖ ⊞ ⊟ ∪ ∨ ⊔ ± ∓ ∔ ∸ ≏ ⊎ ⊻ ⊽ ⋎ ⋓ ⧺ ⧻ ⨈ ⨢ ⨣ ⨤ ⨥ ⨦
⨧ ⨨ ⨩ ⨪ ⨫ ⨬ ⨭ ⨮ ⨹ ⨺ ⩁ ⩂ ⩅ ⩊ ⩌ ⩏ ⩐ ⩒ ⩔ ⩖ ⩗ ⩛ ⩝ ⩡ ⩢ ⩣

• 具有与*相同的优先级:
• parsed with the same precedence as *:

* / ÷ % & ⋅ ∘ × ∩ ∧ ⊗ ⊘ ⊙ ⊚ ⊛ ⊠ ⊡ ⊓ ∗ ∙ ∤ ⅋ ≀ ⊼ ⋄ ⋆ ⋇
⋉ ⋊ ⋋ ⋌ ⋏ ⋒ ⟑ ⦸ ⦼ ⦾ ⦿ ⧶ ⧷ ⨇ ⨰ ⨱ ⨲ ⨳ ⨴ ⨵ ⨶ ⨷ ⨸ ⨻
⨼ ⨽ ⩀ ⩃ ⩄ ⩋ ⩍ ⩎ ⩑ ⩓ ⩕ ⩘ ⩚ ⩜ ⩞ ⩟ ⩠ ⫛ ⊍ ▷ ⨝ ⟕ ⟖ ⟗

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