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| Category: algorithms | | Component type: function |
Prototype
find_first_of is an overloaded name; there are actually two find_first_of functions.
template <class InputIterator, class ForwardIterator>
InputIterator find_first_of(InputIterator first1, InputIterator last1,
ForwardIterator first2, ForwardIterator last2);
template <class InputIterator, class ForwardIterator, class BinaryPredicate>
InputIterator find_first_of(InputIterator first1, InputIterator last1,
ForwardIterator first2, ForwardIterator last2,
BinaryPredicate comp);
Description
Find_first_of is similar to find, in that it performs linear seach through a range of InputIterator. The difference is that while find searches for one particular value, find_first_of searches for any of several values. Specifically, find_first_of searches for the first occurrance in the range [first1, last1) of any of the elements in [first2, last2). (Note that this behavior is reminiscent of the function strpbrk from the standard C library.)
The two versions of find_first_of differ in how they compare elements for equality. The first uses operator==, and the second uses and arbitrary user-supplied functors comp. The first version returns the first iterator i in [first1, last1) such that, for some iterator j in [first2, last2), *i == *j. The second returns the first iterator i in [first1, last1) such that, for some iterator j in [first2, last2), comp(*i, *j) is true. As usual, both versions return last1 if no such iterator i exists.
Definition
Defined in the standard header algorithm, and in the nonstandard backward-compatibility header algo.h.
Requirements on types
For the first version:
For the second version:
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InputIterator is a model of InputIterator.
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ForwardIterator is a model of ForwardIterator.
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BinaryPredicate is a model of BinaryPredicate.
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InputIterator's value type is convertible to BinaryPredicate's first argument type.
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ForwardIterator's value type is convertible to BinaryPredicate's second argument type.
Preconditions
-
[first1, last1) is a valid range.
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[first2, last2) is a valid range.
Complexity
At most (last1 - first1) * (last2 - first2) comparisons.
Example
Like strpbrk, one use for find_first_of is finding whitespace in a string; space, tab, and newline are all whitespace characters.
int main()
{
const char* WS = "\t\n ";
const int n_WS = strlen(WS);
char* s1 = "This sentence contains five words.";
char* s2 = "OneWord";
char* end1 = find_first_of(s1, s1 + strlen(s1),
WS, WS + n_WS);
char* end2 = find_first_of(s2, s2 + strlen(s2),
WS, WS + n_WS);
printf("First word of s1: %.*s\n", end1 - s1, s1);
printf("First word of s2: %.*s\n", end2 - s2, s2);
}
Notes
See also
find, find_if, search
