Iterators

Novum uses a lazy iterator abstraction for sequence pipelines.

Automatic iterable conversion

Users normally do not need to call .iter() manually. Iterable values are automatically converted to an iterator when an iterator method is requested.

For example:

[1, 2, 3]
    .map(|x| x * 2)
    .filter(|x| x > 2)
    .collect()

The following classes of values can participate in the iterator protocol where implemented:

• Iterator
• List
• Str
• Range
• Dict
• Set, where available
• Vector

Matrix iteration is deliberately not treated as a generic iterable until its element semantics are fixed.

Core methods

The iterator API includes:

map(callback)
filter(callback)
enumerate()
zip(other)
take(n)
skip(n)
collect()
reduce(callback)
fold(initial, callback)
any(callback)
all(callback)

The exact callback contract for reduction methods follows the runtime implementation and should be checked against tests when writing reusable code.

map

[1, 2, 3]
    .map(|x| x * 2)
    .collect()

filter

[1, 2, 3, 4]
    .filter(|x| x % 2 == 0)
    .collect()

enumerate

"abc"
    .enumerate()
    .collect()

zip

Method form:

[1, 2, 3].zip([4, 5, 6])

Global functional form is also supported:

zip([1, 2, 3], [4, 5, 6])

The arguments to zip can be ordinary iterable values; explicit .iter() calls are not required.

Laziness

Iterator adaptors such as map, filter, take, and skip produce iterators. collect() materializes the values into a list.

let result =
    (1..100)
        .filter(|x| x % 2 == 0)
        .take(10)
        .collect()