Returns a sequence from a starting value to, but not including, an end value, stepping by the specified amount.
SDK
- Xcode 8.0+
Framework
- Swift Standard Library
Declaration
func stride<T>(from start: T, to end: T, by stride: T.Stride) -> StrideParameters
startThe starting value to use for the sequence. If the sequence contains any values, the first one is
start.endAn end value to limit the sequence.
endis never an element of the resulting sequence.strideThe amount to step by with each iteration. A positive
strideiterates upward; a negativestrideiterates downward.
Return Value
A sequence from start toward, but not including, end. Each value in the sequence steps by stride.
Discussion
You can use this function to stride over values of any type that conforms to the Strideable protocol, such as integers or floating-point types. Starting with start, each successive value of the sequence adds stride until the next value would be equal to or beyond end.
for radians in stride(from: 0.0, to: .pi * 2, by: .pi / 2) {
let degrees = Int(radians * 180 / .pi)
print("Degrees: \(degrees), radians: \(radians)")
}
// Degrees: 0, radians: 0.0
// Degrees: 90, radians: 1.5707963267949
// Degrees: 180, radians: 3.14159265358979
// Degrees: 270, radians: 4.71238898038469
You can use stride(from: to create a sequence that strides upward or downward. Pass a negative value as stride to create a sequence from a higher start to a lower end:
for countdown in stride(from: 3, to: 0, by: -1) {
print("\(countdown)...")
}
// 3...
// 2...
// 1...
If you pass a value as stride that moves away from end, the sequence contains no values.
for x in stride(from: 0, to: 10, by: -1) {
print(x)
}
// Nothing is printed.