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Function std.algorithm.sorting.ordered

Like isSorted, returns true if the given values are ordered according to the comparison operation less. Unlike isSorted, takes values directly instead of structured in a range.

bool ordered(alias less, T...) (
  T values
if (T.length == 2 && is(typeof(binaryFun!less(values[1], values[0])) : bool) || T.length > 2 && is(typeof(ordered!less(values[0..1 + __dollar / 2]))) && is(typeof(ordered!less(values[__dollar / 2..__dollar]))));

ordered allows repeated values, e.g. ordered(1, 1, 2) is true. To verify that the values are ordered strictly monotonically, use strictlyOrdered; strictlyOrdered(1, 1, 2) is false.

With either function, the predicate must be a strict ordering. For example, using "a <= b" instead of "a < b" is incorrect and will cause failed assertions.


values The tested value
less The comparison predicate


true if the values are ordered; ordered allows for duplicates, strictlyOrdered does not.


assert(ordered(42, 42, 43));
assert(!strictlyOrdered(43, 42, 45));
assert(ordered(42, 42, 43));
assert(!strictlyOrdered(42, 42, 43));
assert(!ordered(43, 42, 45));
// Ordered lexicographically
assert(ordered("Jane", "Jim", "Joe"));
assert(strictlyOrdered("Jane", "Jim", "Joe"));
// Incidentally also ordered by length decreasing
assert(ordered!((a, b) => a.length > b.length)("Jane", "Jim", "Joe"));
// ... but not strictly so: "Jim" and "Joe" have the same length
assert(!strictlyOrdered!((a, b) => a.length > b.length)("Jane", "Jim", "Joe"));


Andrei Alexandrescu


Boost License 1.0.