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version 2.109.1

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Template std.algorithm.searching.canFind

Convenience function. Like find, but only returns whether or not the search was successful.

template canFind(alias pred) ;

For more information about pred see find.

Contained Functions

NameDescription
canFind Returns true if and only if pred(e) is true for any value e in the input range range. Performs (at most) Ο(haystack.length) evaluations of pred.
canFind Returns true if and only if needle can be found in range. Performs Ο(haystack.length) evaluations of pred.
canFind Returns the 1-based index of the first needle found in haystack. If no needle is found, then 0 is returned.

See Also

among for checking a value against multiple arguments.

Example

const arr = [0, 1, 2, 3];
assert(canFind(arr, 2));
assert(!canFind(arr, 4));

// find one of several needles
assert(arr.canFind(3, 2));
assert(arr.canFind(3, 2) == 2); // second needle found
writeln(arr.canFind([1, 3], 2)); // 2

assert(canFind(arr, [1, 2], [2, 3]));
writeln(canFind(arr, [1, 2], [2, 3])); // 1
assert(canFind(arr, [1, 7], [2, 3]));
writeln(canFind(arr, [1, 7], [2, 3])); // 2
assert(!canFind(arr, [1, 3], [2, 4]));
writeln(canFind(arr, [1, 3], [2, 4])); // 0

Example

Example using a custom predicate. Note that the needle appears as the second argument of the predicate. 

auto words = [
    "apple",
    "beeswax",
    "cardboard"
];
assert(!canFind(words, "bees"));
assert( canFind!((string elem, string needle) => elem.startsWith(needle))(words, "bees"));

Example

Search for multiple items in an array of items (search for needles in an array of haystacks) 

string s1 = "aaa111aaa";
string s2 = "aaa222aaa";
string s3 = "aaa333aaa";
string s4 = "aaa444aaa";
const hay = [s1, s2, s3, s4];
assert(hay.canFind!(e => e.canFind("111", "222")));

Authors

Andrei Alexandrescu

License

Boost License 1.0.