(C) Array

A way to store a a large number of values and access them by index. There are two kinds of arrays:

Static arrays (size known at compile-time)
Dynamically allocated arrays (size known at run-time)

Take care not to write beyond the bounds of an array.

Static arrays

define ARRAY_SIZE = 10


int main()
{
  /* Create an array */
  int i = 0;
  int array[ARRAY_SIZE];
  /* Initialize it with non-random values */
  for (i=0; i!=ARRAY_SIZE; i++) array[i]=i
  /* Square them */
  for (i=0; i!=ARRAY_SIZE; i++) array[i]*=i
  /* sprintf them */
  /* TODO: sprintf them */
  return 0;
}

How to determine a static array's size?

This can be done from the array's pointer and the size of the zero-th element:

include <assert.h>


define ARRAY_SIZE = 10


int main()
{
  int myArray[ARRAY_SIZE];
  const int size = (sizeof(myArray)/sizeof(myArray[0]));
  assert(size==ARRAY_SIZE);
  return 0;
}

Dynamically allocated arrays

These array's sizes are unknown at ?compile-time and use malloc and ?free.

include <stdio.h>

include <assert.h>


int main()
{
  /* TODO: Convert this to C
  const int randomSize = std::rand()%100;
  int * myArray = new int[randomSize];
  delete[] myArray;
/

  return 0;
}

How to determine a dynamically allocated array's size?

This can NOT[/red] be done from the array's pointer and the size of the zero-th element:

include <stdlib.h>

include <assert.h>


int main()
{
  int randomSize = 2 + rand()%100; /* Can never be 1 */
  /* TODO: Convert this to C
  int * myArray = new int[randomSize];
  const int size = (sizeof(myArray)/sizeof(myArray[0]));
  std::cout << "randomSize: " << randomSize << std::endl;
  std::cout << "size: " << size << std::endl;
  assert(size==1);
  assert(size!=randomSize);
  delete[] myArray;
/

  return 0;
}

'Array' links

C++
C++ class (called boost::array)
C#
PHP

Code links

last edited (November 11, 2006) by bilderbikkel, Number of views: 1733, Current Rev: 2 (Diff)

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