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Template std.algorithm.iteration.filter

filter!(predicate)(range) returns a new range containing only elements x in range for which predicate(x) returns true.

template filter(alias predicate) ;

The predicate is passed to unaryFun, and can be either a string, or any callable that can be executed via pred(element).

Contained Functions

NameDescription
filter

Parameters

NameDescription
predicate Function to apply to each element of range

Returns

An input range that contains the filtered elements. If range is at least a forward range, the return value of filter will also be a forward range.

See Also

Filter (higher-order function), filterBidirectional

Example

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

int[] arr = [ 1, 2, 3, 4, 5 ];

// Filter below 3
auto small = filter!(a => a < 3)(arr);
assert(equal(small, [ 1, 2 ]));

// Filter again, but with Uniform Function Call Syntax (UFCS)
auto sum = arr.filter!(a => a < 3);
assert(equal(sum, [ 1, 2 ]));

// In combination with chain() to span multiple ranges
int[] a = [ 3, -2, 400 ];
int[] b = [ 100, -101, 102 ];
auto r = chain(a, b).filter!(a => a > 0);
assert(equal(r, [ 3, 400, 100, 102 ]));

// Mixing convertible types is fair game, too
double[] c = [ 2.5, 3.0 ];
auto r1 = chain(c, a, b).filter!(a => cast(int) a != a);
assert(isClose(r1, [ 2.5 ]));

Authors

Andrei Alexandrescu

License

Boost License 1.0.