Difference between revisions of "Loops"
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Everything within the body of the loop is considered to be in the scope of the loop. In the case of a for loop, any variable declared in the inializer is considered to be within the scope of the loop. Declaring a variable within the variable within the scope of a loop is highly discouraged. This variable would be difined again everything time the loop iterates, causing a significant waste of memory. | Everything within the body of the loop is considered to be in the scope of the loop. In the case of a for loop, any variable declared in the inializer is considered to be within the scope of the loop. Declaring a variable within the variable within the scope of a loop is highly discouraged. This variable would be difined again everything time the loop iterates, causing a significant waste of memory. | ||
| − | ==Infinite Loops== | + | ==[[Infinite Loops]]== |
An infinite loop is any loop that continues to repeat forever. There are situations where this is useful, but if you didn't intentionally program it in, then it causes a '''fatal''' error for your program. These occur if the test condition in your loop will never be false. Here are a few examples of infinite loops: | An infinite loop is any loop that continues to repeat forever. There are situations where this is useful, but if you didn't intentionally program it in, then it causes a '''fatal''' error for your program. These occur if the test condition in your loop will never be false. Here are a few examples of infinite loops: | ||
Revision as of 15:00, 20 March 2007
(Vic, Roger, David)
Contents
An Introduction
Until now all your programs have been working from top to bottom. Imagine if you were to write a game to guess a secret number from 1 to 100. The entire program would consist of one hundred if statements to account for each turn to check and see if the number chosen is correct; a situation like this is where a loop will come in to play and reduce those one hundred statements into one.
A loop is a control structure that allows you to repeat the same sequence of code as long as a given test condition evaluates to true. Every passage through this sequence of code is called an iteration. If you repeat the same sequence of code 20 times, then you have performed 20 iterations.
Types of Loops
- while -Vic
- for -Roger
- nested loops -Roger
Test Condition
Loops use the test condition to decide whether or not to enter the body of the loop.
Scope
Everything within the body of the loop is considered to be in the scope of the loop. In the case of a for loop, any variable declared in the inializer is considered to be within the scope of the loop. Declaring a variable within the variable within the scope of a loop is highly discouraged. This variable would be difined again everything time the loop iterates, causing a significant waste of memory.
Infinite Loops
An infinite loop is any loop that continues to repeat forever. There are situations where this is useful, but if you didn't intentionally program it in, then it causes a fatal error for your program. These occur if the test condition in your loop will never be false. Here are a few examples of infinite loops:
while(true) //always true
{
}
------------------------------------------------
for(int i = 0; i < 20; i++) //counter reset to 0 every time
{
i = 0;
}
------------------------------------------------
for(int i = 0; i < 9999999999999999; i++) //integers can't be as big as 9999999999999999, so 'i' will overflow to negative
{
}
Additional Information
Review Questions and Exercises
Here you will find some Review Questions and Exercises to help you understand and and learn to use loops.
