朱莉娅函数声明风格 [英] julia function declaration style
问题描述
在Julia中,我知道三种定义命名多行函数的方法:
In Julia, I know of three ways to define a named multiline function:
1.
function f(x, y)
...
end
2.
f = function(x, y)
...
end
3.
f(x, y) = begin
...
end
它们似乎都产生相同的结果.
有什么区别吗?应该使用哪个,为什么?
They all seem to produce the same outcome.
Is there any difference? Which one should be used and why?
推荐答案
1和3在功能上是相同的,但从风格上来说,1是首选. 简短形式函数声明" f(x,y) = …
通常用于(鼓励使用)单行定义,即没有begin
块.
1 and 3 are functionally identical, but 1 is preferred stylistically. The "short form function declaration" f(x,y) = …
is typically used (and encouraged) for one-line definitions — that is, without a begin
block.
2是不同的.它正在创建一个 anonymous 函数,然后将其分配给f
.请注意,与1和3创建的绑定不同,您实际上可以 ressign f
来完全不同.这意味着Julia无法假定f
将始终调用该函数,这意味着它无法进行任何常规优化.现在,如果使用const f = function(x, y) …
,则f
是常量绑定,它的行为应与其他声明类似.但是请注意,f
仍然只是对匿名函数的绑定-函数本身不知道其名称!因此它将打印为#1 (generic function with 1 method)
而不是f (generic function with 1 method)
.
2 is different. It's creating an anonymous function, and then assigning it to f
. Note that unlike the bindings created by 1 and 3, you can actually reassign f
to completely different things. This means that Julia cannot assume that f
will always call that function, which means that it cannot do any of its normal optimizations. Now, if you used const f = function(x, y) …
, then f
is a constant binding and it should behave similarly to the other declarations. But note that f
is still just a binding to an anonymous function — the function itself doesn't know what its name is! So it'll print as #1 (generic function with 1 method)
instead of f (generic function with 1 method)
.
请参见 https://docs.julialang.org/en/stable/manual/功能/以获取更多详细信息.
See https://docs.julialang.org/en/stable/manual/functions/ for more details.
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