Iterating

An iterated operation is a fold over the map that returns the value of type unit, that is, its only use is to produce side-effects. This can be useful if, for example, you would like to check that each value of a map is within a certain range, and fail with an error otherwise.

The predefined functional iterator implementing the iterated operation over maps is called Map.iter. It takes a binding, that is, a key and its associated value in the map, performs some side-effect and returns the unit value.

In the following example, a map is iterated to check that all its integer values are greater than 3.

const assert_all_greater_than_3 =

(m: map<int,int>) : unit => Map.iter(([_k,v]) => assert(v > 3), m);

Note: See the predefined namespace Map