Step by Step solution about How to resolve the algorithm Averages/Simple moving average step by step in the C programming language

The provided C code implements a simple sliding window moving average (SMA) library. Let's break down the code step by step:

1. Header Includes:

   #include <stdio.h>
   #include <stdlib.h>
   #include <stdarg.h>

   These headers include standard input/output functions, dynamic memory allocation functions, and support for variable argument lists (stdarg.h).

2. Custom Types and Structs:

   • sma_obj_t: This struct represents an SMA object. It contains the following fields:

     • sma: The current SMA value.
     • sum: The sum of the values in the sliding window.
     • period: The period of the SMA (i.e., the number of values in the sliding window).
     • values: An array to store the values in the sliding window.
     • lv: The current level (index) in the values array.

   • sma_result_t: This union represents the result of an SMA operation. It can either contain a pointer to an SMA object (handle), the current SMA value (sma), or an array of values (values).

3. sma() Function:

   This function is the core of the SMA library. It takes an enum Action and a variable number of arguments (...) to perform various operations on SMA objects.

   • SMA_NEW: Creates a new SMA object with the specified period and returns a pointer to it.

   • SMA_FREE: Frees the memory allocated for an SMA object.

   • SMA_VALUES: Returns the values array of an SMA object.

   • SMA_MEAN: Returns the current sma value of an SMA object.

   • SMA_ADD: Adds a new value to an SMA object and updates the SMA calculation.

4. Main Function:

   int main()
   {
    int i;
   
    sma_obj_t *h3 = sma(SMA_NEW, 3).handle;
    sma_obj_t *h5 = sma(SMA_NEW, 5).handle;
   
    for(i=0; i < sizeof(v)/sizeof(double) ; i++) {
      printf("next number %lf, SMA_3 = %lf, SMA_5 = %lf\n",
             v[i], sma(SMA_ADD, h3, v[i]).sma, sma(SMA_ADD, h5, v[i]).sma);
    }
   
    sma(SMA_FREE, h3);
    sma(SMA_FREE, h5);
    return 0;
   }

   • This is the entry point of the program.

   • It initializes two SMA objects, h3 with a period of 3 and h5 with a period of 5.

   • A loop iterates through a pre-defined array v and adds each value to both SMA objects. It prints the original value, the SMA values for each object, and the updated SMA values.

   • Finally, it frees the memory allocated for the SMA objects.

In summary, this code demonstrates how to create and use an SMA library to calculate moving averages of a stream of values. It provides a flexible interface to perform common SMA operations, such as creating new objects, updating SMA calculations, and retrieving SMA values.

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>

typedef struct sma_obj {
  double sma;
  double sum;
  int period;
  double *values;
  int lv;
} sma_obj_t;

typedef union sma_result {
  sma_obj_t *handle;
  double sma;
  double *values;
} sma_result_t;

enum Action { SMA_NEW, SMA_FREE, SMA_VALUES, SMA_ADD, SMA_MEAN };
sma_result_t sma(enum Action action, ...)
{
  va_list vl;
  sma_result_t r;
  sma_obj_t *o;
  double v;

  va_start(vl, action);
  switch(action) {
  case SMA_NEW: // args: int period
    r.handle = malloc(sizeof(sma_obj_t));
    r.handle->sma = 0.0;
    r.handle->period = va_arg(vl, int);
    r.handle->values = malloc(r.handle->period * sizeof(double));
    r.handle->lv = 0;
    r.handle->sum = 0.0;
    break;
  case SMA_FREE: // args: sma_obj_t *handle
    r.handle = va_arg(vl, sma_obj_t *);
    free(r.handle->values);
    free(r.handle);
    r.handle = NULL;
    break;
  case SMA_VALUES: // args: sma_obj_t *handle
    o = va_arg(vl, sma_obj_t *);
    r.values = o->values;
    break;
  case SMA_MEAN: // args: sma_obj_t *handle
    o = va_arg(vl, sma_obj_t *);
    r.sma = o->sma;
    break;
  case SMA_ADD: // args: sma_obj_t *handle, double value
    o = va_arg(vl, sma_obj_t *);
    v = va_arg(vl, double);
    if ( o->lv < o->period ) {
      o->values[o->lv++] = v;
      o->sum += v;
      o->sma = o->sum / o->lv;
    } else {
      o->sum -= o->values[ o->lv % o->period];
      o->sum += v;
      o->sma = o->sum / o->period;
      o->values[ o->lv % o->period ] = v; o->lv++;
    }
    r.sma = o->sma;
    break;
  }
  va_end(vl);
  return r;
}


double v[] = { 1, 2, 3, 4, 5, 5, 4, 3, 2, 1 };

int main()
{
  int i;

  sma_obj_t *h3 = sma(SMA_NEW, 3).handle;
  sma_obj_t *h5 = sma(SMA_NEW, 5).handle;

  for(i=0; i < sizeof(v)/sizeof(double) ; i++) {
    printf("next number %lf, SMA_3 = %lf, SMA_5 = %lf\n",
	   v[i], sma(SMA_ADD, h3, v[i]).sma, sma(SMA_ADD, h5, v[i]).sma);
  }

  sma(SMA_FREE, h3);
  sma(SMA_FREE, h5);
  return 0;
}