The For Loop

We write code like this :

   int i;

   i = startvalue
   while (test_involving i) {
      statements
      change_the_value_of_i
   }

that they have implemented another control structure. The structure is called a for loop.

   for (initialization; condition; increment) {
      statements
   }

It performs exactly as the above loop.

The initialization statement is performed
The condition is checked, if it is false, we exit the loop
Otherwise we execute the statemtnts
We execute the increment
We go back to step two.

For example, to count from 1 to 10

   int i;

   i = 1;
   while (i <= 10) {
      cout << " I is " << i << endl;
      i++;
   }

   or 

   for (i=1;i<=10;i++) {
      cout << " I is " << i << endl;
   }

The while is more general purpose
- The increment doesn't need to be at the end of a loop only
- It has been in almost every language
The for statement is special purpose
- Our authors tell us that it is intended mainly for counter controlled loops
- This is not my experience.
None of the fields must be filled in,
- for (i=0;;) {
- i = 0; while (1);
- for (;x<7;) {
- while (x<7){

How about this code


// assume menu returns a choice a-d
char ch;

ch = menu()
while(('a' <= ch ) && (ch <= 'd') ) {
   ch = menu();
}

for(ch=menu(); ('a' <= ch ) && (ch <= 'd'); ch=menu()) ;