funcs_filtering.go

package handy

import (
    "github.com/hsldymq/goiter"
    "iter"
)

func filter[T any](e Iterable[T], predicate func(T) bool) Enumerable[T] {
    return NewEnumerator(goiter.Filter(e.Iter(), predicate))
}

func distinct[T any](e Enumerable[T]) Enumerable[T] {
    typeComparable := isTypeComparable[T]()
    _, comparableImpl := any(zVal[T]()).(Comparable)
    if comparableImpl {
        return distinctBy(e, func(v T) any { return any(v).(Comparable).ComparingKey() })
    } else if typeComparable {
        return distinctBy(e, func(v T) any { return v })
    } else {
        return e
    }
}

func distinctBy[T any](e Iterable[T], keySelector func(v T) any) Enumerable[T] {
    seq := func(yield func(T) bool) {
        yielded := map[any]bool{}

        next, stop := iter.Pull(e.Iter())
        defer stop()
        for {
            v, ok := next()
            if !ok {
                return
            }
            k := keySelector(v)
            if yielded[k] {
                continue
            }
            yielded[k] = true
            if !yield(v) {
                return
            }
        }
    }
    return NewEnumerator(seq)
}