# reduce(op, itr)

reduce(op, itr)

Like `reduce(op, v0, itr)`. This cannot be used with empty collections, except for some special cases (e.g. when `op` is one of `+`, `*`, `max`, `min`, `&`, `|`) when Julia can determine the neutral element of `op`.

## Examples

``````julia> reduce(-, 1:5)
-13``````
``````julia> reduce(+, 1:5)
15``````
1. Calculate the sum of an array:

``````julia> arr = [1, 2, 3, 4, 5];
julia> reduce(+, 0, arr)
15``````

This example uses the `reduce` function to calculate the sum of all elements in the array `arr`. The `+` operator is used as the binary operator, and `0` is the neutral element for addition.

2. Find the maximum value in a collection:

``````julia> collection = [7, 2, 9, 5, 1];
julia> reduce(maximum, collection)
9``````

Here, the `reduce` function is used with the `maximum` function to find the maximum value in the collection.

3. Concatenate strings in a collection:

``````julia> strings = ["Hello", ", ", "world", "!"];
julia> reduce(*, strings)
"Hello, world!"``````

In this example, the `reduce` function is used with the `*` operator to concatenate the strings in the collection.

4. Handle empty collections with a default value:
``````julia> empty_collection = Int[];
julia> reduce(+, 0, empty_collection)
0``````

When reducing an empty collection, the `v0` value (in this case, `0`) is returned as the result.

Note: It is recommended to use specialized functions like `sum`, `prod`, `maximum`, etc., when applicable, as they have optimized implementations for specific operations.