为持久变量生成代码

% y = compute_average(x)
% This function takes an input scalar value 'x' and returns the average
% value so far.
function y = compute_average(x) %#codegen
assert(isa(x,'double')); % Input is scalar double

% Declare two persistent variables 'sum' and 'cnt'.
persistent sum cnt;

% Upon the first call we need to initialize the variables.
if isempty(sum)
    sum = 0;
    cnt = 0;
end

% Compute the accumulated sum and the number of values so far.
sum = sum + x;
cnt = cnt + 1;

% Return the current average.
y = sum / cnt;

Code generation successful.

ans = 
10

ans = 
15

ans = 
43.3333

ans = 
10

ans = 
15

ans = 
20

ans = 
25

/*
 * File: main.c
 */
/* Include Files */
#include "main.h"
#include "compute_average.h"
#include "compute_average_terminate.h"
#include "compute_average_initialize.h"

/* Function Declarations */
static double argInit_real_T(void);
static void main_compute_average(void);

/* Function Definitions */
/*
 * Arguments    : void
 * Return Type  : double
 */
static double argInit_real_T(void)
{
  return 0.0;
}

/*
 * Arguments    : void
 * Return Type  : void
 */
static void main_compute_average(void)
{
  double y;

  /* Initialize function 'compute_average' input arguments. */
  /* Call the entry-point 'compute_average'. */
  y = compute_average(argInit_real_T());
}

/*
 * Arguments    : int argc
 *                const char * const argv[]
 * Return Type  : int
 */
int main(int argc, const char * const argv[])
{
  (void)argc;
  (void)argv;
  
  /* Initialize the entry-point function. */
  compute_average_initialize();
  
  /* Invoke the entry-point functions.
     You can call entry-point functions multiple times. */
  main_compute_average();

  /* Terminate the application. */
  compute_average_terminate();
  
  /*Once the application is terminated, the state of the persistent variables is cleared. */
  
  /* Re-initialize the entry-point function. */
  compute_average_initialize();
  
  /* You can run the application for a new set of values.*/
  main_compute_average();
  
  /* Terminate the application after your process is complete.*/
  compute_average_terminate();
  
  return 0;
}

/*
 * File trailer for main.c
 *
 * [EOF]
 */