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limit.go
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limit.go
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package seq
import (
"github.com/kamstrup/fn/opt"
)
type limitSeq[T any] struct {
seq Seq[T]
limit int
}
// LimitOf returns a lazy seq with the first limit elements.
// Normally you would call the Limit(n) method on a seq, but there are cases where this function is the only option.
func LimitOf[T any](seq Seq[T], limit int) Seq[T] {
if limit <= 0 {
return Empty[T]()
} else if sz, ok := seq.Len(); ok && sz <= limit {
return seq
}
return limitSeq[T]{
seq: seq,
limit: limit,
}
}
func (l limitSeq[T]) ForEach(f Func1[T]) opt.Opt[T] {
var (
i = 0
head opt.Opt[T]
tail Seq[T]
)
for head, tail = l.seq.First(); i < l.limit && head.Ok(); head, tail = tail.First() {
v, _ := head.Return()
f(v)
i++
}
return opt.Zero[T]()
}
func (l limitSeq[T]) ForEachIndex(f Func2[int, T]) opt.Opt[T] {
var (
i = 0
head opt.Opt[T]
tail Seq[T]
)
for head, tail = l.seq.First(); i < l.limit && head.Ok(); head, tail = tail.First() {
v, _ := head.Return()
f(i, v)
i++
}
return opt.Zero[T]()
}
func (l limitSeq[T]) Len() (int, bool) {
sz, ok := l.seq.Len()
if ok {
if sz < l.limit {
return sz, true
}
return l.limit, true
}
// len not well-defined
if sz == LenInfinite {
return l.limit, true
}
return LenUnknown, false
}
func (l limitSeq[T]) ToSlice() Slice[T] {
arr, _ := l.Take(l.limit)
return arr
}
func (l limitSeq[T]) Limit(n int) Seq[T] {
if n < l.limit {
return LimitOf[T](l, n)
}
return l
}
func (l limitSeq[T]) Take(n int) (Slice[T], Seq[T]) {
if n > l.limit {
n = l.limit
}
head, tail := l.seq.Take(n)
return head, LimitOf(tail, l.limit-len(head))
}
func (l limitSeq[T]) TakeWhile(pred Predicate[T]) (Slice[T], Seq[T]) {
i := -1
head, tail := l.seq.TakeWhile(func(t T) bool {
i++
return i < l.limit && pred(t)
})
return head, LimitOf(tail, l.limit-i)
}
func (l limitSeq[T]) Skip(n int) Seq[T] {
if n > l.limit {
return Empty[T]()
}
return LimitOf(l.seq.Skip(n), l.limit-n)
}
func (l limitSeq[T]) Where(pred Predicate[T]) Seq[T] {
return WhereOf[T](l, pred)
}
func (l limitSeq[T]) While(pred Predicate[T]) Seq[T] {
return WhileOf[T](l, pred)
}
func (l limitSeq[T]) First() (opt.Opt[T], Seq[T]) {
fst, tail := l.seq.First()
return fst, LimitOf(tail, l.limit-1)
}
func (l limitSeq[T]) Map(f FuncMap[T, T]) Seq[T] {
return MappingOf[T, T](l, f)
}