View source code
Display the source code in std/range/package.d from which this
page was generated on github.
Report a bug
If you spot a problem with this page, click here to create a
Bugzilla issue.
Improve this page
Quickly fork, edit online, and submit a pull request for this page.
Requires a signed-in GitHub account. This works well for small changes.
If you'd like to make larger changes you may want to consider using
local clone.
Function std.range.chooseAmong
Choose one of multiple ranges at runtime.
auto chooseAmong(Ranges...)
(
size_t index,
scope return Ranges rs
)
if (Ranges .length >= 2 && allSatisfy!(isInputRange, staticMap!(Unqual, Ranges)) && !is(CommonType!(staticMap!(ElementType, Ranges)) == void));
The ranges may be different, but they must have compatible element types. The
result is a range that offers the weakest capabilities of all Ranges
.
Parameters
Name | Description |
---|---|
index | which range to choose, must be less than the number of ranges |
rs | two or more ranges |
Returns
The indexed range. If rs consists of only one range, the return type is an alias of that range's type.
Example
auto test()
{
import std .algorithm .comparison : equal;
int[4] sarr1 = [1, 2, 3, 4];
int[2] sarr2 = [5, 6];
int[1] sarr3 = [7];
auto arr1 = sarr1[];
auto arr2 = sarr2[];
auto arr3 = sarr3[];
{
auto s = chooseAmong(0, arr1, arr2, arr3);
auto t = s .save;
writeln(s .length); // 4
writeln(s[2]); // 3
s .popFront();
assert(equal(t, only(1, 2, 3, 4)));
}
{
auto s = chooseAmong(1, arr1, arr2, arr3);
writeln(s .length); // 2
s .front = 8;
assert(equal(s, only(8, 6)));
}
{
auto s = chooseAmong(1, arr1, arr2, arr3);
writeln(s .length); // 2
s[1] = 9;
assert(equal(s, only(8, 9)));
}
{
auto s = chooseAmong(1, arr2, arr1, arr3)[1 .. 3];
writeln(s .length); // 2
assert(equal(s, only(2, 3)));
}
{
auto s = chooseAmong(0, arr1, arr2, arr3);
writeln(s .length); // 4
writeln(s .back); // 4
s .popBack();
s .back = 5;
assert(equal(s, only(1, 2, 5)));
s .back = 3;
assert(equal(s, only(1, 2, 3)));
}
{
uint[5] foo = [1, 2, 3, 4, 5];
uint[5] bar = [6, 7, 8, 9, 10];
auto c = chooseAmong(1, foo[], bar[]);
writeln(c[3]); // 9
c[3] = 42;
writeln(c[3]); // 42
writeln(c .moveFront()); // 6
writeln(c .moveBack()); // 10
writeln(c .moveAt(4)); // 10
}
{
import std .range : cycle;
auto s = chooseAmong(0, cycle(arr2), cycle(arr3));
assert(isInfinite!(typeof(s)));
assert(!s .empty);
writeln(s[100]); // 8
writeln(s[101]); // 9
assert(s[0 .. 3] .equal(only(8, 9, 8)));
}
return 0;
}
// works at runtime
auto a = test();
// and at compile time
static b = test();
Authors
Andrei Alexandrescu, David Simcha, Jonathan M Davis, and Jack Stouffer. Credit for some of the ideas in building this module goes to Leonardo Maffi.
License
Copyright © 1999-2022 by the D Language Foundation | Page generated by ddox.