The predicate for comparing each element with the needle, defaulting to equality "a == b". The negated predicate "a != b" can be used to search instead for the first element not matching the needle.
The input range searched in.
The element searched for.
haystack advanced such that the front element is the one searched for; that is, until binaryFun!pred(haystack.front, needle) is true. If no such position exists, returns an empty haystack.
import std.container : SList; import std.range.primitives : empty; import std.typecons : Tuple; assert(find("hello, world", "World").empty); assert(find("hello, world", "wo") == "world"); assert([1, 2, 3, 4].find(SList!int(2, 3)[]) == [2, 3, 4]); alias C = Tuple!(int, "x", int, "y"); auto a = [C(1,0), C(2,0), C(3,1), C(4,0)]; assert(a.find!"a.x == b"([2, 3]) == [C(2,0), C(3,1), C(4,0)]); assert(a[1 .. $].find!"a.x == b"([2, 3]) == [C(2,0), C(3,1), C(4,0)]);
import std.range.primitives; auto arr = [1, 2, 4, 4, 4, 4, 5, 6, 9]; assert(arr.find(4) == [4, 4, 4, 4, 5, 6, 9]); assert(arr.find(1) == arr); assert(arr.find(9) == [9]); assert(arr.find!((a, b) => a > b)(4) == [5, 6, 9]); assert(arr.find!((a, b) => a < b)(4) == arr); assert(arr.find(0).empty); assert(arr.find(10).empty); assert(arr.find(8).empty); assert(find("hello, world", ',') == ", world");
Case-insensitive find of a string
import std.range.primitives; import std.uni : toLower; string[] s = ["Hello", "world", "!"]; assert(s.find!((a, b) => toLower(a) == b)("hello") == s);
auto arr = [ 1, 2, 3, 4, 1 ]; assert(find!("a > 2")(arr) == [ 3, 4, 1 ]); // with predicate alias bool pred(int x) { return x + 1 > 1.5; } assert(find!(pred)(arr) == arr);
Finds an individual element in an input range. Elements of haystack are compared with needle by using predicate pred with pred(haystack.front, needle). find performs O(walkLength(haystack)) evaluations of pred.
The predicate is passed to std.functional.binaryFun, and can either accept a string, or any callable that can be executed via pred(element, element).
To find the last occurrence of needle in a bidirectional haystack, call find(retro(haystack), needle). See std.range.retro.
If no needle is provided, pred(haystack.front) will be evaluated on each element of the input range.
If input is a forward range, needle can be a forward range too. In this case startsWith!pred(haystack, needle) is evaluated on each evaluation.
Note: find behaves similar to dropWhile in other languages.
Complexity: find performs O(walkLength(haystack)) evaluations of pred. There are specializations that improve performance by taking advantage of bidirectional or random access ranges (where possible).