CODEWITHSUNDEEP
erlangerlang-shell
Piskator
Piskator

Reputation: 647

lists:any true in false cases?

I run the following anonymous function and variables in the interpreter, and get wrongly so a true statement, but why is that, and what do I need to change:

Lst = [1,2,3].
Y = 52.
lists:any(fun(Y) -> lists:member(Y, Lst) end, Lst).

Upvotes: 1

Views: 76

Answers (1)

legoscia
legoscia

Reputation: 41568

This is because the Y in the argument list of the fun shadows the outer definition of Y. It therefore checks if any list element is a member of the list, which is always true.

You don't actually need lists:any here; you can call lists:member directly, without lists:any:

> lists:member(Y, Lst).
false

The equivalent using lists:any would be:

> lists:any(fun(X) -> X =:= Y end, Lst).             
false

Here, the argument is X, so we can access Y from outside the fun.

Upvotes: 3

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