{{alias}}( frac, exp )
    Multiplies a double-precision floating-point number by an integer power of
    two; i.e., `x = frac * 2^exp`.

    If `frac` equals positive or negative `zero`, `NaN`, or positive or negative
    infinity, the function returns a value equal to `frac`.

    Parameters
    ----------
    frac: number
        Fraction.

    exp: number
        Exponent.

    Returns
    -------
    out: number
        Double-precision floating-point number equal to `frac * 2^exp`.

    Examples
    --------
    > var x = {{alias}}( 0.5, 3 )
    4.0
    > x = {{alias}}( 4.0, -2 )
    1.0
    > x = {{alias}}( 0.0, 20 )
    0.0
    > x = {{alias}}( -0.0, 39 )
    -0.0
    > x = {{alias}}( NaN, -101 )
    NaN
    > x = {{alias}}( {{alias:@stdlib/constants/float64/pinf}}, 11 )
    Infinity
    > x = {{alias}}( {{alias:@stdlib/constants/float64/ninf}}, -118 )
    -Infinity

    See Also
    --------