The MPL Reference Manual: shift_left

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# shift_left

### Synopsis

    template<
          typename T
        , typename Shift
        >
    struct shift_left
    {
        typedef unspecified type;
    };

### Description

Returns the result of bitwise shift left (`<<`) operation on `T`.

### Header

    #include <boost/mpl/shift_left.hpp>
    #include <boost/mpl/bitwise.hpp>

### Model of

Numeric Metafunction

### Parameters

Parameter | Requirement | Description
--- | --- | ---
`T` | Integral Constant | A value to shift.
`Shift` | Unsigned Integral Constant | A shift distance.

[Note: The requirements listed in this specification are the ones imposed by the default implementation. See Numeric Metafunction concept for the details on how to provide an implementation for a user-defined numeric type that does not satisfy the Integral Constant requirements. — end note]

### Expression semantics

For arbitrary Integral Constant `c` and unsigned Integral Constant `shift`:

    typedef shift_left<c,shift>::type r;

Return type: | Integral Constant.
Semantics: | Equivalent to
    typedef integral_c<
          c::value_type
        , ( c::value << shift::value )
        > r;

    typedef shift_left<c,shift> r;

Return type: | Integral Constant.
Semantics: | Equivalent to
    struct r : shift_left<c,shift>::type {};

### Complexity

Amortized constant time.

### Example

    typedef integral_c<unsigned,0> u0;
    typedef integral_c<unsigned,1> u1;
    typedef integral_c<unsigned,2> u2;
    typedef integral_c<unsigned,8> u8;

    BOOST_MPL_ASSERT_RELATION( (shift_left<u0,u0>::value), ==, 0 );
    BOOST_MPL_ASSERT_RELATION( (shift_left<u1,u0>::value), ==, 1 );
    BOOST_MPL_ASSERT_RELATION( (shift_left<u1,u1>::value), ==, 2 );
    BOOST_MPL_ASSERT_RELATION( (shift_left<u2,u1>::value), ==, 4 );
    BOOST_MPL_ASSERT_RELATION( (shift_left<u8,u1>::value), ==, 16 );

### See also

Bitwise Operations, Numeric Metafunction, numeric_cast, shift_right, bitand_