formIndex(_:offsetBy:limitedBy:)

Declaration

func formIndex(_ i: inout Self.Index, offsetBy distance: Int, limitedBy limit: Self.Index) -> Bool

Parameters

• i:

  A valid index of the collection.

• distance:

  The distance to offset i. distance must not be negative unless the collection conforms to the BidirectionalCollection protocol.

• limit:

  A valid index of the collection to use as a limit. If distance > 0, a limit that is less than i has no effect. Likewise, if distance < 0, a limit that is greater than i has no effect.

Return Value

true if i has been offset by exactly distance steps without going beyond limit; otherwise, false. When the return value is false, the value of i is equal to limit.

Discussion

The value passed as distance must not offset i beyond the bounds of the collection, unless the index passed as limit prevents offsetting beyond those bounds.