Software Design Using C++
Loop Properties
The following summarizes some of the basic properties of loops in C++.
This can be useful in deciding which loop to use and in avoiding problems
in coding. See also the Programming Patterns
section for some commonly-used patterns involving loops.
- Number of times to do the loop body must be known in advance?
- WHILE loop: no
- DO..WHILE loop: no
- FOR loop: no
A FOR loop in C++ can do anything the WHILE loop can; it is very general.
However, the answer is yes for a straightforward counting loop.
Here is an example of how such a counting loop might be set up.
Note that the Count must be known ahead of time:
for (k = 0; k < Count; k++)
cout << k << endl;
- Minimum number of times that the loop body is executed:
- WHILE loop: 0
- DO..WHILE loop: 1
This is because the condition is tested at the bottom of the loop.
- FOR loop: 0
- Can give an infinite loop?
- WHILE loop: yes
- DO..WHILE loop: yes
- FOR loop: yes
However, if set up correctly as a straightforward
counting loop the answer is no. See above for an example
of such a counting loop. (Note that it is important that
the loop body does not modify k , the loop control
variable. For example, if we changed this example so that the
loop body decremented k by 1, using a statement
such as k-- , then overall the value of k would
not change and we would have an infinite loop. In effect,
the k-- and the k++ would cancel
each other out.
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