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import gleam/int
import gleam/result as res
import gleam/dict.{type Dict}
import gleam/iterator.{type Iterator, Next} as iter
pub fn count(iterator: Iterator(a), satisfying predicate: fn(a) -> Bool) -> Int {
iterator
|> iter.filter(keeping: predicate)
|> iter.length
}
pub fn counts(iterator: Iterator(a)) -> Dict(a, Int) {
iterator
|> iter.fold(from: dict.new(), with: fn(acc, value) {
acc
|> dict.insert(
value,
dict.get(acc, value)
|> res.unwrap(or: 0)
|> int.add(1),
)
})
}
pub fn filter_map(
iterator: Iterator(a),
with mapper: fn(a) -> Result(b, c),
) -> Iterator(b) {
iterator
|> iter.flat_map(with: fn(elem) {
case mapper(elem) {
Ok(new) -> iter.single(new)
Error(_) -> iter.empty()
}
})
}
pub fn unfold_infinitely(from state: a, with fun: fn(a) -> a) -> Iterator(a) {
iter.unfold(from: state, with: fn(s) { Next(element: s, accumulator: fun(s)) })
}
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