next

next(iter, state) -> item, state

For a given iterable object and iteration state, return the current item and the next iteration state

Examples

julia> foo = [1,2,4,8];
julia> state = start(foo);
julia> while !done(foo, state)
            (i, state) = next(foo, state)
            println(i*i)
        end                 # semantics of a for loop
1
4
16
64

Iterate through elements of a collection:
```
julia> words = ["apple", "banana", "cherry"];
julia> state = nothing;
julia> item, state = next(words, state)
("apple", 2)
```
In this example, next is used to iterate through the elements of the words collection. The initial state is set to nothing and each subsequent call to next returns the current item and the updated state.
Iterate through a range of numbers:
```
julia> r = 1:5;
julia> state = nothing;
julia> for _ in r
          item, state = next(r, state)
          println(item)
       end
1
2
3
4
5
```
This example demonstrates how next can be used within a loop to iterate through a range of numbers. The current item is printed at each iteration.

Iterate through a custom iterable object with state:

julia> struct MyIterable
           data::Vector{Int}
           state::Int
       end
julia> Base.iterate(iterable::MyIterable, state) = state > length(iterable.data) ? nothing : (iterable.data[state], state + 1)
julia> mydata = MyIterable([10, 20, 30, 40, 50], 1);
julia> state = mydata.state;
julia> item, state = next(mydata, state)
(10, 2)

In this example, a custom iterable object MyIterable is defined. The next function is used to iterate through the data vector of MyIterable by updating the state.

Common mistake example:

julia> numbers = [1, 2, 3, 4, 5];
julia> state = 6;
julia> item, state = next(numbers, state)
ERROR: MethodError: no method matching iterate(::Array{Int64,1}, ::Int64)

In this example, the provided state value is out of bounds for the collection. It's important to ensure that the state is a valid iteration state within the range of the collection to avoid such errors. Always check that the state is within the valid range before using next.

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Examples

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