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Template std.algorithm.iteration.each

Eagerly iterates over r and calls pred over each element.

If no predicate is specified, each will default to doing nothing but consuming the entire range. .front will be evaluated, but this can be avoided by explicitly specifying a predicate lambda with a lazy parameter.

each also supports opApply-based iterators, so it will work with e.g. std.parallelism.parallel.

Arguments

template each(alias pred);

Functions

Function name Description
each
each

Parameters

NameDescription
pred predicate to apply to each element of the range
r range or iterable over which each iterates

See Also

std.range.tee

Example

import std.range : iota;

long[] arr;
iota(5).each!(n => arr ~= n);
writeln(arr); // [0, 1, 2, 3, 4]

// If the range supports it, the value can be mutated in place
arr.each!((ref n) => n++);
writeln(arr); // [1, 2, 3, 4, 5]

arr.each!"a++";
writeln(arr); // [2, 3, 4, 5, 6]

// by-ref lambdas are not allowed for non-ref ranges
static assert(!is(typeof(arr.map!(n => n).each!((ref n) => n++))));

// The default predicate consumes the range
auto m = arr.map!(n => n);
(&m).each();
assert(m.empty);

// Indexes are also available for in-place mutations
arr[] = 0;
arr.each!"a=i"();
writeln(arr); // [0, 1, 2, 3, 4]

// opApply iterators work as well
static class S
{
    int x;
    int opApply(scope int delegate(ref int _x) dg) { return dg(x); }
}

auto s = new S;
s.each!"a++";
writeln(s.x); // 1

Authors

Andrei Alexandrescu

License

Boost License 1.0.

Comments