/*****************************************************************************
*                                                                            *
*   LOG2.SPL   Copyright (C) 1999 DSP Development Corporation                *
*                               All Rights Reserved                          *
*                                                                            *
*   Author:      Randy Race                                                  *
*                                                                            *
*   Synopsis:    Calculates log base 2 of the input                          *
*                                                                            *
*   Revisions:   19 Mar 1999  RRR  Creation                                  *
*                                                                            *
*****************************************************************************/

#if @HELP_LOG2

    LOG2

    Purpose: Returns Log base 2 of the input.

    Syntax:  LOG2(expr)

             expr - Any expression evaluating to a scalar, series, or table.

    Returns: A real, series or table

    Example:
             Log2(1024)

             returns 10


             Log2({2, 4, 8, 16})

             returns the series {1, 2, 3, 4}

    Remarks:
             Log2 is useful for manipulating the lengths of FFT calculations.

    See Also:
             Log
             Log10
#endif



/* calculate log base 2 */
log2(x)
{
        local z, a, n, s;

        if (argc < 1) error("log2 - input required");

        if (outargc > 1)
        {
                /* x = s + 2^e */
                z = x == 0;
                a = z + mag(x);
                n = not(z) * (floor(log(a) / log(2)) + 1);
                s = sign(x) * a / (2 ^ n);

                /* significand and exponent */
                return(s, n);
        }
        else
        {
                /* log 2*/
                return(log(x) / log(2));
        }
}