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`std.algorithm.searching.find` - multiple declarations

Function find

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 Ο(walkLength(haystack)) evaluations of pred.


						
				InputRange find(alias pred, InputRange, Element)
				(
				

				  InputRange haystack,
				

				  scope Element needle
				

				)
				

				if (isInputRange!InputRange && is(typeof(binaryFun!pred(haystack.front, needle)) : bool));
				

				

				InputRange find(alias pred, InputRange)
				(
				

				  InputRange haystack
				

				)
				

				if (isInputRange!InputRange);
				

				

				R1 find(alias pred, R1, R2)
				(
				

				  R1 haystack,
				

				  scope R2 needle
				

				)
				

				if (isForwardRange!R1 && isForwardRange!R2 && is(typeof(binaryFun!pred(haystack.front, needle.front)) : bool));

The predicate is passed to 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 Ο(walkLength(haystack)) evaluations of pred. There are specializations that improve performance by taking advantage of bidirectional or random access ranges (where possible).

Parameters

Name	Description
pred	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.
haystack	The input range searched in.
needle	The element searched for.

Returns

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.

Example

import std.range.primitives;

auto arr = [1, 2, 4, 4, 4, 4, 5, 6, 9];
writeln(arr.find(4)); // [4, 4, 4, 4, 5, 6, 9]
writeln(arr.find(1)); // arr
writeln(arr.find(9)); // [9]
writeln(arr.find!( (a, b) => a > b)(4)); // [5, 6, 9]
writeln(arr.find!( (a, b) => a < b)(4)); // arr
assert(arr.find(0).empty);
assert(arr.find(10).empty);
assert(arr.find(8).empty);

writeln(find("hello, world", ',')); // ", world"

Example

Case-insensitive find of a string

import std.range.primitives;
import std.uni : toLower;

string[] s = ["Hello", "world", "!"];
writeln(s.find!( (a, b) => toLower(a) == b)("hello")); // s

Example

auto arr = [ 1, 2, 3, 4, 1 ];
writeln(find!("a > 2")(arr)); // [3, 4, 1]

// with predicate alias
bool pred(int x) { return x + 1 > 1.5; }
writeln(find!(pred)(arr)); // arr

Example

import std.container : SList;
import std.range.primitives : empty;
import std.typecons : Tuple;

assert(find("hello, world", "World").empty);
writeln(find("hello, world", "wo")); // "world"
writeln([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)];
writeln(a.find!"a.x == b"([2, 3])); // [C(2, 0), C(3, 1), C(4, 0)]
writeln(a[1 .. $].find!"a.x == b"([2, 3])); // [C(2, 0), C(3, 1), C(4, 0)]

Function find

Finds two or more needles into a haystack. The predicate pred is used throughout to compare elements. By default, elements are compared for equality.


						
				Tuple!(Range,size_t) find(alias pred, Range, Ranges...)
				(
				

				  Range haystack,
				

				  Ranges needles
				

				)
				

				if (Ranges.length > 1 && is(typeof(startsWith!pred(haystack, needles))));

Parameters

Name	Description
pred	The predicate to use for comparing elements.
haystack	The target of the search. Must be an input range. If any of `needles` is a range with elements comparable to elements in `haystack`, then `haystack` must be a forward range such that the search can backtrack.
needles	One or more items to search for. Each of `needles` must be either comparable to one element in `haystack`, or be itself a forward range with elements comparable with elements in `haystack`.

Returns

A tuple containing haystack positioned to match one of the needles and also the 1-based index of the matching element in needles (0 if none of needles matched, 1 if needles[0] matched, 2 if needles[1] matched...). The first needle to be found will be the one that matches. If multiple needles are found at the same spot in the range, then the shortest one is the one which matches (if multiple needles of the same length are found at the same spot (e.g "a" and 'a'), then the left-most of them in the argument list matches).

The relationship between haystack and needles simply means that one can e.g. search for individual ints or arrays of ints in an array of ints. In addition, if elements are individually comparable, searches of heterogeneous types are allowed as well: a double[] can be searched for an int or a short[], and conversely a long can be searched for a float or a double[]. This makes for efficient searches without the need to coerce one side of the comparison into the other's side type.

The complexity of the search is Ο(haystack.length * max(needles.length)). (For needles that are individual items, length is considered to be 1.) The strategy used in searching several subranges at once maximizes cache usage by moving in haystack as few times as possible.

Example

import std.typecons : tuple;
int[] a = [ 1, 4, 2, 3 ];
writeln(find(a, 4)); // [4, 2, 3]
writeln(find(a, [1, 4])); // [1, 4, 2, 3]
writeln(find(a, [1, 3], 4)); // tuple([4, 2, 3], 2)
// Mixed types allowed if comparable
writeln(find(a, 5, [1.2, 3.5], 2.0)); // tuple([2, 3], 3)

Function find

Finds needle in haystack efficiently using the Boyer-Moore method.


						
				RandomAccessRange find(RandomAccessRange, alias pred, InputRange)
				(
				

				  RandomAccessRange haystack,
				

				  scope BoyerMooreFinder!(pred,InputRange) needle
				

				);

Parameters

Name	Description
haystack	A random-access range with length and slicing.
needle	A `BoyerMooreFinder`.

Returns

haystack advanced such that needle is a prefix of it (if no such position exists, returns haystack advanced to termination).

Example

import std.range.primitives : empty;
int[] a = [ -1, 0, 1, 2, 3, 4, 5 ];
int[] b = [ 1, 2, 3 ];

writeln(find(a, boyerMooreFinder(b))); // [1, 2, 3, 4, 5]
assert(find(b, boyerMooreFinder(a)).empty);

Authors

Andrei Alexandrescu

License

Boost License 1.0.

API Documentation

`std.algorithm.searching.find` - multiple declarations

Function find

Note

Complexity

Parameters

Returns

See ALso

Example

Example

Example

Example

Function find

Parameters

Returns

Example

Function find

Parameters

Returns

Example

Authors

License

API Documentation

std.algorithm.searching.find - multiple declarations

Function find

Note

Complexity

Parameters

Returns

See ALso

Example

Example

Example

Example

Function find

Parameters

Returns

Example

Function find

Parameters

Returns

Example

Authors

License

`std.algorithm.searching.find` - multiple declarations