Erlang 模式与别名匹配
是否有可能在函数定义中匹配元组的某些子集，并且仍然在方法中获得完整的元组？
我想做的是这样的：
myfun({ foo, Bar }: Var) -> otherfunction(Var, stuff).
而不是：
myfun({ foo, Bar }) -> otherfunction({ foo, Bar }, stuff).
我希望这足够清楚。
谢谢。
is there a possibility to match in a function definition do some subset of a touple and still get get complete touple in the method ?
What I would like to do is something like this:
myfun({ foo, Bar }: Var) -> otherfunction(Var, stuff).
instead of:
myfun({ foo, Bar }) -> otherfunction({ foo, Bar }, stuff).
I hope this is clear enough.
Thanks.
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您可以通过在前面添加下划线来忽略某些参数。例如
myfun( {foo, _Bar, Var } )将通过忽略 _Bar 参数来匹配。这就是你的想法吗？
或者您的意思是：
myfun( {foo, Bar} = Var ) ->; otherfun( Var ).在这种情况下，如果与 myfun 匹配成功，则 Var 将在 otherfun 中使用。原因是：Var 在表达式求值时未绑定，因此将被分配给 {foo, Bar}。
You can ignore some parameters by putting an underscore in front. E.g.
myfun( {foo, _Bar, Var } )will match by ignoring the _Bar parameter. Is that what you had in mind?
Or did you mean:
myfun( {foo, Bar} = Var ) -> otherfun( Var ).in this case, Var will be used in otherfun iff the match with myfun succeeded. The reason is: Var is un-bound at the time of evaluation of the expression and thus will be assigned to {foo, Bar}.
也许这就是你的意思：
这样，你就可以将你的函数导出为 myfun/1 （一个参数）。它只会匹配具有两个元素的元组。第一个必须是“foo”原子，而第二个可以是任何东西。在所有其他情况下，您都会得到一个函数子句，除非您为该函数指定不同的子句。例如，这样写是有意义的：
不过，我不完全确定这就是您所要求的。请告诉我这是否有帮助。
Maybe this is what you meant:
In this way, you can export your function as myfun/1 (one parameter). It will match just on tuples with two elements. The first one must be the "foo" atom, while the second can be anything. You will get a function clause in all other cases, unless you specify different clauses for the function. For example, it would make sense to have:
I'm not completely sure this is what you're asking, though. Please, let me know if this helped.
如果我的说法正确，那么您想要的是设置
Var，仅包含一个匹配的{ foo, Bar }，而无需执行任何额外的检查，例如简洁的缘故。据我所知，你不能在 Erlang 中做到这一点。对不起。 :)
If I have this correct, what you want is to have
Varto be set, containing only a touple matching{ foo, Bar }without having to do any additional checks, for conciseness sake.As far as I've ever seen, you can't do this in Erlang. Sorry. :)