The D Programming Language's Unofficial Docs
beta
The D Programming Language's Unofficial Docs
beta
Function to apply to each element of range
filter!(predicate)(range) returns a new range containing only elements x in range for which predicate(x) returns true.
1 import std.algorithm.comparison : equal; 2 import std.math : approxEqual; 3 import std.range; 4 5 int[] arr = [ 1, 2, 3, 4, 5 ]; 6 7 // Filter below 3 8 auto small = filter!(a => a < 3)(arr); 9 assert(equal(small, [ 1, 2 ])); 10 11 // Filter again, but with Uniform Function Call Syntax (UFCS) 12 auto sum = arr.filter!(a => a < 3); 13 assert(equal(sum, [ 1, 2 ])); 14 15 // In combination with chain() to span multiple ranges 16 int[] a = [ 3, -2, 400 ]; 17 int[] b = [ 100, -101, 102 ]; 18 auto r = chain(a, b).filter!(a => a > 0); 19 assert(equal(r, [ 3, 400, 100, 102 ])); 20 21 // Mixing convertible types is fair game, too 22 double[] c = [ 2.5, 3.0 ]; 23 auto r1 = chain(c, a, b).filter!(a => cast(int) a != a); 24 assert(approxEqual(r1, [ 2.5 ]));
Implements the higher order filter function. The predicate is passed to std.functional.unaryFun, and can either accept a string, or any callable that can be executed via pred(element).