find_first_of


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 Input Iterators. 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 usersupplied function object 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
backwardcompatibility header algo.h.
Requirements on types
For the first version:
For the second version:

InputIterator is a model of Input Iterator.

ForwardIterator is a model of Forward Iterator.

BinaryPredicate is a model of Binary Predicate.

InputIterator's value type is convertible to
BinaryPredicate's first argument type.

ForwardIterator's value type is convertible to
BinaryPredicate's second argument type.
Preconditions

[first1, last1) is a valid range.

[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
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