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version 2.109.1

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Function std.range.iota

Creates a range of values that span the given starting and stopping values.

auto iota(B, E, S) (
  B begin,
  E end,
  S step
)
if ((isIntegral!(CommonType!(B, E)) || isPointer!(CommonType!(B, E))) && isIntegral!S);

auto iota(B, E) (
  B begin,
  E end
)
if (isFloatingPoint!(CommonType!(B, E)));

auto iota(B, E) (
  B begin,
  E end
)
if (isIntegral!(CommonType!(B, E)) || isPointer!(CommonType!(B, E)));

auto iota(E) (
  E end
)
if (is(typeof(iota(E(0), end))));

auto iota(B, E, S) (
  B begin,
  E end,
  S step
)
if (isFloatingPoint!(CommonType!(B, E, S)));

auto iota(B, E) (
  B begin,
  E end
)
if (!isIntegral!(CommonType!(B, E)) && !isFloatingPoint!(CommonType!(B, E)) && !isPointer!(CommonType!(B, E)) && is(typeof((ref B b) { ++b; } )) && (is(typeof(B.init < E.init)) || is(typeof(B.init == E.init))));

Parameters

NameDescription
begin The starting value.
end The value that serves as the stopping criterion. This value is not included in the range.
step The value to add to the current value at each iteration.

Returns

A range that goes through the numbers begin, begin + step, begin + 2 * step, ..., up to and excluding end.

The two-argument overloads have step = 1. If begin < end && step < 0 or begin > end && step > 0 or begin == end, then an empty range is returned. If step == 0 then begin == end is an error.

For built-in types, the range returned is a random access range. For user-defined types that support ++, the range is an input range.

An integral iota also supports in operator from the right. It takes the stepping into account, the integral won't be considered contained if it falls between two consecutive values of the range. contains does the same as in, but from lefthand side.

Example

void main()
{
    import std.stdio;

    // The following groups all produce the same output of:
    // 0 1 2 3 4

    foreach (i; 0 .. 5)
        writef("%s ", i);
    writeln();

    import std.range : iota;
    foreach (i; iota(0, 5))
        writef("%s ", i);
    writeln();

    writefln("%(%s %|%)", iota(0, 5));

    import std.algorithm.iteration : map;
    import std.algorithm.mutation : copy;
    import std.format;
    iota(0, 5).map!(i => format("%s ", i)).copy(stdout.lockingTextWriter());
    writeln();
}

Example

import std.algorithm.comparison : equal;
import std.math.operations : isClose;

auto r = iota(0, 10, 1);
assert(equal(r, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]));
assert(equal(r, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]));
assert(3 in r);
assert(r.contains(3)); //Same as above
assert(!(10 in r));
assert(!(-8 in r));
r = iota(0, 11, 3);
assert(equal(r, [0, 3, 6, 9]));
writeln(r[2]); // 6
assert(!(2 in r));
auto rf = iota(0.0, 0.5, 0.1);
assert(isClose(rf, [0.0, 0.1, 0.2, 0.3, 0.4]));

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

Boost License 1.0.