问题描述
When I use the for loop in Playground, everything worked fine, until I changed the first parameter of for loop to be the highest value. (iterated in descending order)
Is this a bug? Did any one else have it?
for index in 510..509
{
var a = 10
}
The counter that displays the number of iterations that will be executions keeps ticking...
Xcode 6 beta 4 added two functions to iterate on ranges with a step other than one:stride(from: to: by:)
, which is used with exclusive ranges and stride(from: through: by:)
, which is used with inclusive ranges.
To iterate on a range in reverse order, they can be used as below:
for index in stride(from: 5, to: 1, by: -1) {
print(index)
}
//prints 5, 4, 3, 2
for index in stride(from: 5, through: 1, by: -1) {
print(index)
}
//prints 5, 4, 3, 2, 1
Note that neither of those is a Range
member function. They are global functions that return either a StrideTo
or a StrideThrough
struct, which are defined differently from the Range
struct.
A previous version of this answer used the by()
member function of the Range
struct, which was removed in beta 4. If you want to see how that worked, check the edit history.
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