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filter.go
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filter.go
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// MIT License
// Copyright (c) 2022 Brian Reece
package iterator
// FilterPredicate is a function that returns true
// if the item should be included in the resulting
// iterator.
type FilterFunc[T any] func(*T) bool
// Filter transforms an iterator by filtering out
// items based on a predicate function.
type Filter[T any] struct {
iter Iterator[T]
pred FilterFunc[T]
}
// NewFilter constructs a new Filter over an iterator, using pred.
func NewFilter[T any](iter Iterator[T], pred FilterFunc[T]) *Filter[T] {
return &Filter[T]{iter, pred}
}
// Next returns the next item in the Filter. Returns nil, error
// on collection error.
func (f *Filter[T]) Next() (*T, error) {
for {
item, err := f.iter.Next()
if item == nil {
return nil, nil
}
if !(f.pred)(item) {
continue
}
if err != nil {
return item, err
}
return item, nil
}
}
// Any returns true if for any item in the iterator,
// pred returns true. Returns false, error upon collection
// error.
func Any[T any](iter Iterator[T], pred FilterFunc[T]) (bool, error) {
for {
item, err := iter.Next()
if item == nil {
break
}
if err != nil {
return false, err
}
if (pred)(item) {
return true, nil
}
}
return false, nil
}
// All returns true if for all items in the iterator,
// pred returns true. Returns false, error upon collection
// error.
func All[T any](iter Iterator[T], pred FilterFunc[T]) (bool, error) {
for {
item, err := iter.Next()
if item == nil {
break
}
if err != nil {
return true, err
}
if !(pred)(item) {
return false, nil
}
}
return true, nil
}
// None returns true if for all items in the iterator,
// pred returns false. Returns false, error upon collection
// error.
func None[T any](iter Iterator[T], pred FilterFunc[T]) (bool, error) {
for {
item, err := iter.Next()
if item == nil {
break
}
if err != nil {
return true, err
}
if (pred)(item) {
return false, err
}
}
return true, nil
}