# Issue

How can I check if the set is empty, I have implemented the following code if the set has an empty set then I should get the value true else false, for example: [1; 2; []] this set should result in true and if the set is [1; 2; 3] this should result in false because this one does not have an empty set in it. Following is the code that gives me an error:

```
let rec isEmpty S =
match S with
|[] -> true
|_ -> false
|e::rest -> ([]=e) || (isEmpty [] rest)
```

# Solution

Unfortunately for your use case F# is quite a bit more 'strongly typed' than you would like here.

In F# a value like [1; 2; 3] is an int list, and an int list won't accept a value like [1; 2; []].

Maybe you could try to define a new (recursive) datatype for your problem.

Answered By - Robert Nielsen Answer Checked By - Senaida (PHPFixing Volunteer)

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