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It Indexof

docs/data/it-indexof.md

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Returns the index at which the first occurrence of a value is found in the sequence, or -1 if the value is not found. Scans the sequence from the beginning and returns the position of the first matching element.

go
// Find existing element - returns first occurrence
seq := func(yield func(int) bool) {
    _ = yield(10)
    _ = yield(20)
    _ = yield(30)
    _ = yield(20)
}
idx := it.IndexOf(seq, 20)
// idx: 1 (first occurrence of 20)
go
// Element not found - returns -1
seq := func(yield func(string) bool) {
    _ = yield("apple")
    _ = yield("banana")
    _ = yield("cherry")
}
idx := it.IndexOf(seq, "orange")
// idx: -1 (orange not found in sequence)
go
// Empty sequence - returns -1
emptySeq := func(yield func(string) bool) {
    // no elements yielded
}
idx := it.IndexOf(emptySeq, "anything")
// idx: -1 (sequence is empty)