用户定义的中缀运算符

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 usingthe 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 andotherwise manipulate like any other function. However, Julia's parser isconfigured to recognize a certain set of symbols as infix operators; if youdefine a function whose name is one of these symbols, it will be parsed as aninfix 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 Juliaparser sourcecode. Forthe 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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