User-defined infix operator

Question

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

julia> +(1, 2)
3

Howeve

Answer 1

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.

For example:

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

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).

At the moment, it includes for example:

• parsed with the same precedence as +:

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

• parsed with the same precedence as *:

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