| Each function definition can only have one loop. |
It must be possible to do a loop's body more than once [Loop is not loop: 1-3 points]
| Do not use while to mean if. If you write a loop, there should exist some circumstances where the loop body can be done more than once. |
Do not mix loops and recursion [Loop with recursion: 1-4 points]
| A function that contains a loop must not also use recursion. |
If code is only performed at the end of the last iteration of a loop, then it should be written after the loop. If code is only performed at the beginning of the first iteration, it should be written before the loop. [Loop end: 1-2 point]
Look at the following example.
int loopdemo(int n)
{
for(int i = 0; i < n; i++)
{
doSomething(i);
if(i == n-1)
{
finish(i+1);
}
}
}
Notice that statement finish(i+1) is only done at the end of the
last iteration of the loop. This function should be written
as follows.
int loopdemo(int n)
{
for(int i = 0; i < n; i++)
{
doSomething(i);
}
finish(n);
}
|
Do not change the value of a for-loop control variable in the loop body [For body changes control variable: 1-3 points]
A for-loop
control variable (any variable that is modified in the third
part of a for-loop heading) should only be modified in the for-loop heading,
not in the body of the loop. For example, do not write
for(i = 1; i < n; i++)
{
...
i = n;
...
}
If you want to break out of a loop, use break or return.
|
Do not change a for-loop end value in the loop without justification [For body changes end: 1-3 points]
Do not change the end-value of a for-loop just as a way to get
out of the loop. For example,
for(i = 1; i < n; i++)
{
...
if(condition)
{
n = 0;
}
...
}
is not a good way to cause the loop to end. If you want to
exit a for-loop, use break or return.
|
Initialize for a for-loop in the heading where sensible [For loop initialization: 1-2 points]
| The first component of a for-loop heading is for initializing the control variable. Use it unless you have a good reason for not using it. |
Do not simulate two nested loops or two consecutive loops using a single loop. [Nested loop simulation: 2-8 points]
It is possible to do a lot in a single loop by managing variables in
complicated ways. Imagine that you want to do two nested for-loops,
as follows.
for(int i = 0; i < n; i++)
{
for(int j = 0; j < m; j++)
{
doSomething(i,j);
}
}
But that uses two loops, so you simulate it with one loop, as follows.
int i = 0;
int j = 0;
while(i < n)
{
doSomething(i,j);
j++;
if(j == m)
{
j = 0;
i++;
}
}
You can recognize this by the reset of j to 0 when
j = m.
That is not an acceptable way to avoid two loops in one function. Just write a function to handle the inner loop.
void doAll(int i)
{
for(int j = 0; j < m; j++)
{
doSomething(i,j);
}
}
Now your loop becomes
for(int i = 0; i < n; i++)
{
doAll(i);
}
|