传播赋值

在分解赋值中，将 ... 放在变量前面会将所有剩余元素展开到该变量中。这称为扩展赋值。

[x,...y] = [1, 2, 3]
assert x == 1
assert y == [2, 3]
x, ...y = (1, 2, 3)
assert x == 1
assert y == (2, 3)

提取赋值

如果在 ... 之后没有写入任何内容，则忽略并分配剩余的元素。这种类型的扩展赋值具体称为抽取赋值。提取分配是一种方便的语法，用于本地化模块或记录中的特定属性。

{sin; cos; tan; ..} = import "math"

After that, you can use sin, cos, tan locally.

You can do the same with records.

record = {x = 1; y = 2}
{x; y; ...} = record

If you want to expand all, use {*} = record. It is open in OCaml.

record = {x = 1; y = 2}
{*} = records
assert x == 1 and y == 2