Idiom # 54: Compute sum of integers

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Code

The simplest way is using the generic feature sum that can be applied to all numeric types.

Using fold shows a more generic way: fold is the feature of choice to join elements of a set into a value of the element type. For type i32, such operations are defined in the unit type returned by feature i32. To build the sum, i32.sum is the operation to use.

Mathematically speaking, such an operation is called a monoid. This is why the type of the argument of fold is Monoid, while the operations declared for i32 inherit from Monoid.

Running Example