我想在 Julia 中编写一个合并两个字典的函数。

function merge(left::Dict, right::Dict)::Dict

语义如下：

• 输入left为right
• left和都right拥有其数据的所有权，这意味着它们将在函数调用后被修改，并且不应对它们包含的数据做出任何保证
• 返回值包含两个字典的数据
• 如果任何键同时存在于两者中left，并且right值left保持不变

以下是关于如何解决此问题的一些初步想法。（这是带有注释的伪代码，而不是可以实际编译的代码。）

function mergeDict(left::Dict, right::Dict)::Dict

    # create a new dictionary from `left`
    return_value = left

    # move data from `right` to `left`, "no-clobber"
    for k, v in pop_next!(right)
    # the function `pop_next!` does not exist, no iterator-like `pop!`

    for k in keys(right)
        v = pop!(right, k)
        # does this work as expected? destructive operation while reading keys?
        # `keys()` returns an *iterator*, not a collection! (?)

        if !haskey(left, k)
            push!(left, k, v) # no `push!` function
            left[k] = v # this works instead
        end
    end
    
    # `left` and `right` are not pointers, but "copy-by-value references"
    # just as in Python, so this doesn't work
    left = nothing
    right = nothing

    # we want to invalidate the data, how to do that?
    # this also won't work because `left` references the same data
    # structure as `return_value`
    clear(left)
    clear(right)
end

您可以看到，我尝试编写手动实现。我确信 Julia 会有一些有用的函数作为标准库的一部分来实现这一点，但是由于我是 Julia 新手，我不知道这些函数是什么。

我找到了函数merge、和mergewith，然而这些函数似乎都不具备上面描述的语义。merge!mergewith!