#include <../../nrnconf.h>

/******************************************************************************
 *
 * File: ramp.c
 *
 * Copyright (c) 1984-1991
 *   Duke University
 *
 ******************************************************************************/

#ifndef LINT
static char RCSid[] =
    "ramp.c,v 1.1.1.1 1994/10/12 17:22:23 hines Exp" ;
#endif

/*-----------------------------------------------------------------------------
 *
 *  RAMP()
 *
 *    Computes the value of a ramp function of specified height
 *    and duration
 *
 *  Calling sequence:
 *	ramp(t, lag, height, duration)
 *
 *  Arguments:
 *    Input:	t, double	the independent variable,
 *				usually time
 *
 *		lag, double	value of t at which ramp begins
 *
 *		height, double	ramp height
 *
 *		duration,double duration of the ramp incline
 *
 *    Output:  reset_integ, *int  set to 1 if discontinuity is
 *                              generated                     
 *              old_value, *double  saved value from previous
 *                              call                         
 *
 *  Returns:
 *	Double precision value of the ramp function
 *
 *  Functions called:
 *	none
 *
 *  Files accessed:
 *	none
 *
 */


double 
ramp(reset_integ, old_value, t, lag, height, duration)
double *old_value, t, lag, height, duration;
int *reset_integ;
{
    if (t < lag)
    {
	if (*old_value != 0.) *reset_integ = 1;
	*old_value = 0.;
	return (0.0);
    }
    else if (t > lag + duration)
    {
	if (*old_value != height) *reset_integ = 1;
	*old_value = height;
	return (height);
    }
    else
    {
	if (*old_value == 0. || *old_value == height) *reset_integ = 1;
	*old_value = (t - lag) * height / duration;
	return (*old_value);
    }
}