```
assoc(x, xys)
```

Return the first element from the association list `xys`

whose head is equivalent to `x`

.
Return `false`

if the element is not found.

An association list is a proper list whose elements are pairs of the
form `key:value`

.

The equivalence test for `assoc`

is `is_equal`

.

```
assoc("b", ["a":1, "b":2, "c":3])
// b:2
```