# equal_to

### Synopsis

    template<
          typename T1
        , typaname T2
        >
    struct equal_to
    {
        typedef unspecified type;
    };

### Description

Returns `true_c` if `T1::value == T2::value` and `false_c` otherwise [1].

### Definition

    #include "boost/mpl/comparison/equal_to.hpp"

### Parameters

Parameter | Requirement | Description
--- | --- | ---
`T1, T2` | A model of Integral Constant |

### Expression semantics

Expression | Expression type | Precondition | Semantics | Postcondition
--- | --- | --- | --- | ---
`typedef equal_to<t1,t2>::type c;` | A model of `bool` Integral Constant |  | Equivalent to `typedef bool_c<(t1::value == t2::value)> c;` |

### Complexity

Amortized constant time.

### Example

    typedef list_c<int,1,2,3,5,7,12,19,31> fibonacci;
    typedef find_if< fibonacci, equal_to<_,int_c<12> > >::type iter;
    BOOST_STATIC_ASSERT(equal_to< distance< begin<fibonacci>::type, iter >::type, int_c<5> >::type::value));

### Notes

[1] The `equal_to` metafunction can be (and is expected to be) specialized by user to work on user-defined types that do not satisfy the Integral Constant requirements. The requirements listed here are the ones imposed by the default implementation.

### See also

Metafunctions, `not_equal_to`, `less`, `less_equal`, `greater`, `greater_equal`

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Last edited July 17, 2002 4:13 am