Like Java C++ allows you arrays of anything. All elements must be of the same type. The starting subscript is zero. The starting subscript cannot be changed to 1 ( remember VB). The name of the array also represents the first element in the array. It is also a constant value during the program execution. It cannot be an lvalue. The array name by itself cannot appear on the left hand side.
lvalues: represent storage locations that can have their contents altered by the program - they usually appear on the left side of an assignment.
int iarray[3]; // array of 3 integers
char carray[12]; // a string array - note strings in C++ are character arrays
It is recommended practice to set the size of an array using a variable
#define X_VERTMAX = 7
double xvert[X_VERTMAX];
Arrays are intialized to zero by default. Arrays can also be explicitly declared and initialized:
double xvert[X_VERTMAX] = { 0.0, 0.3, 0.5, 1.0};
// Note you do not have to initialize all values
// some compilers will complain if you provide more
// values then the declared length of array
char string1[] = "Bezier Curve";
// the size of the array is the number of elements
// initialized with
If you are using an empty size in the declaration you must initialize the array as it will be taken as a zero array. You will not be able to assign any elements to it later. It will kill neighboring information.
int size_xvert ;
size_vert = (int) sizeof(xvert);
// returns number of bytes used by the array xvert
Multidimensional Arrays
Like Java multidimensional arrays are defined by additional squate brackets
double coeff [4][4];
Multidimensional arrays are stored as a single dimensional array within the computer. Multidimensional arrays can be ininitialized in the form defined.
Lets write a snippet to check out program control
In this program we will
read a line of input from screen
parse them into words
use program control procedures
use string manipulation function
/*
// a snippet to look at program control and
// string/character input and output
// hacked from Pappas/Murray
*/
#include <iostream.h>
#include <string.h> // contains functions for string handling
#define MAX_LENGTH 80 // good idea to capitalize constants
#define EXIT 0 // define constants
int main()
{
char cLine[MAX_LENGTH + 1]; // this is a string
char cWords[MAX_LENGTH + 1]; // another string
char sWords[20][MAX_LENGTH + 1]; // a string array - note 2d char array
// string variables need one more space for string terminator \0
int iChrs = 0;
int iWords = 1;
int iW = 0;
int ivar;
do
{ cout << "Enter a sentence expressing your feeling about B Curve \n\n";
cin.getline(cLine, MAX_LENGTH); // reads a string from console
} while (cLine[0] == '\0'); // the prompt will keep appearing
// until a string is entered
// example of a do-while
while (cLine[iChrs] != '\0') // just while
{ if (cLine[iChrs] != ' ') // this program assumes words are
// seperated by one blank character
{ cWords[iW] = cLine[iChrs];
iW++;
} else
{ strcpy(sWords[iWords - 1], cWords); // built in string copy function
for (ivar = 0; ivar < iW ; ivar++)
cWords[ivar] = ' ';
iWords++;
iW = 0;
}
iChrs++;
} strcpy(sWords[iWords-1],cWords); // copy the last word
cout << "\nYou wrote: " << cLine << "\n" << endl;
cout << "which included " << iChrs << " characters\n\n";
cout << "which included " << iWords << " words\n";
for (iW = 0; iW < iWords ; iW++)
cout << " The words are: " << sWords[iW] << endl;
cout << "\n\n";
return EXIT;
}
