在朱莉娅中键入kwargs [英] Typed kwargs in Julia

问题描述

是否可以在Julia中键入函数kwargs?

以下内容适用于标准Vararg.

function int_args(args::Integer...)
    args
end

int_args(1, 2, 3)
# (1, 2, 3)

int_args(1, 2, 3.0)
# ERROR: MethodError: `int_args` has no method matching int_args(::Int64, ::Int64, ::Float64)

但是，将相同的语法应用于kwargs时，所有函数调用似乎都出错.

function int_kwargs(; kwargs::Integer...)
    kwargs
end

int_kwargs(x=1, y=2)
# ERROR: MethodError: `__int_kwargs#0__` has no method matching __int_kwargs#0__(::Array{Any,1})

解决方案

普通关键字参数可以具有类型，如function f(x; a::Int=0)所示，但这不适用于其余"关键字参数.还要注意，由于我们当前不分派关键字参数，因此在这种情况下，a::Int是类型声明，而不是分派规范.

看起来这种情况不能很好地处理，并且至少需要更好的错误消息.我鼓励您在 https://github.com/JuliaLang/julia/issues 上提出问题.. >

我不确定关键字参数的语法x::T...应该意味着什么.对于varargs，很明显x的每个元素都应具有T类型，但是对于rest关键字参数，每个元素实际上是一个符号-值对.当然，我们可以给它提供您所描述的含义(所有值的类型均为T)，但这似乎很少出现.关键字参数往往是非常不同的，与varargs不同，而varargs更像是列表或数组.

Is it possible to type function kwargs in Julia?

The following works for standard Varargs.

function int_args(args::Integer...)
    args
end

int_args(1, 2, 3)
# (1, 2, 3)

int_args(1, 2, 3.0)
# ERROR: MethodError: `int_args` has no method matching int_args(::Int64, ::Int64, ::Float64)

However, when applying this same syntax to kwargs, all function calls seem to error.

function int_kwargs(; kwargs::Integer...)
    kwargs
end

int_kwargs(x=1, y=2)
# ERROR: MethodError: `__int_kwargs#0__` has no method matching __int_kwargs#0__(::Array{Any,1})

解决方案

Normal keyword arguments can have types, as in function f(x; a::Int=0), but this doesn't work for "rest" keyword arguments. Also note that since we currently don't dispatch on keyword arguments, the a::Int in this case is a type assertion and not a dispatch specification.

It looks like this case is not handled well, and needs a better error message at least. I'd encourage you to file an issue at https://github.com/JuliaLang/julia/issues.

I'm not sure what the syntax x::T... should mean for keyword arguments. In the case of varargs, it's clear that each element of x should have type T, but for rest keyword arguments each element is actually a symbol-value pair. Of course we could give it the meaning you describe (all values have type T), but this doesn't seem to come up very often. Keyword arguments tend to be quite heterogeneous, unlike varargs which are more like lists or arrays.

这篇关于在朱莉娅中键入kwargs的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！