/* harmonicDemo1.c: Functions to calculate a harmonic function of a
 * given amplitude and phase.  The desired amplitude and phase are
 * passed as arguments to harmonicInit1().  harmonicInit1() sets the
 * corresponding static global variables so that these values will be
 * available for the harmonic1() function to use whenever it is
 * called.
 */

#include <math.h> // for cos() function

/* Global static variables that are visible only to functions inside
   this file. */
static double amp, phase;     

// initialization function
void harmonicInit1(double the_amp, double the_phase) {  
  amp = the_amp;       
  phase = the_phase;   

  return;
}

// calculation function
double harmonic1(double x) {   
  return amp * cos(x + phase);
}