/*****************************************************************************
*                                                                            *
*   HAVERSIN.SPL  Copyright (C) 2020 DSP Development Corporation             *
*                               All Rights Reserved                          *
*                                                                            *
*   Author:       Randy Race                                                 *
*                                                                            *
*   Synopsis:     Evaluates a haversin function                              *
*                                                                            *
*   Revisions:    12 May 2020  RRR  Creation                                 *
*                                                                            *
*****************************************************************************/

#if @HELP_HAVERSIN

    HAVERSIN

    Purpose: Calculates the haversin of any expression.

    Syntax:  HAVERSIN(val)

              val - A scalar, series or table.

    Returns: A scalar, series or table depending on the input value.

    Example:
             W1: haversin(0..pi/100..2*pi)

             Generates the haversin from 0 to 2*pi radians.
 
    Example:
             t = 0..0.01..1;
             haversin(2*pi*3*t);

             Create a 101 point series of a 3 Hz haversin sampled at 100
             samples per second.
 
    Remarks:
             The haversin function is defined as:

               haversin(theta) = sin(theta/2)^2 = (1 - cos(theta)) / 2

             See GHAVERSIN to generate a haversin with a specified length
             and delta x.

    See Also:
             Ghaversin
             Gsin
             Sin
#endif


/* evaluates a haversin function */
haversin(theta)
{
        if (argc < 1) error(sprintf("%s - input required", __FUNC__));

        return(0.5 * (1 - cos(theta)));
}