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| Category: algorithms | | Component type: function |
Prototype
Equal is an overloaded name; there are actually two equal functions.
template <class InputIterator1, class InputIterator2>
bool equal(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2);
template <class InputIterator1, class InputIterator2,
class BinaryPredicate>
bool equal(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, BinaryPredicate binary_pred);
Description
Equal returns true if the two ranges [first1, last1) and [first2, first2 + (last1 - first1)) are identical when compared element-by-element, and otherwise returns false. [1]
The first version of equal returns true if and only if for every iterator i in [first1, last1), *i == *(first2 + (i - first1)). The second version of equal returns true if and only if for every iterator i in [first1, last1), binary_pred(*i, *(first2 + (i - first1)) is true.
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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InputIterator1 is a model of InputIterator.
-
InputIterator2 is a model of InputIterator.
-
BinaryPredicate is a model of BinaryPredicate.
-
InputIterator1's value type is convertible to BinaryPredicate's first argument type.
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InputIterator2's value type is convertible to BinaryPredicate's second argument type.
Preconditions
-
[first1, last1) is a valid range.
-
[first2, first2 + (last2 - last1)) is a valid range.
Complexity
Linear. At most last1 - first1 comparisons.
Example
int A1[] = { 3, 1, 4, 1, 5, 9, 3 };
int A2[] = { 3, 1, 4, 2, 8, 5, 7 };
const int N = sizeof(A1) / sizeof(int);
cout << "Result of comparison: " << equal(A1, A1 + N, A2) << endl;
Notes
[1] Note that this is very similar to the behavior of mismatch: The only real difference is that while equal will simply return false if the two ranges differ, mismatch returns the first location where they do differ. The expression equal(f1, l1, f2) is precisely equivalent to the expression mismatch(f1, l1, f2).first == l1, and this is in fact how equal could be implemented.
See also
mismatch, search, find, find_if
