Each function definition can only have one loop. |
It must be possible to do a loop's body more than once [10 points each, 3% max]
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. |
A function that contains a loop must not also use recursion. |
Do not emulate two nested loops or two consecutive loops using a single loop. [40 points each, 7% max]
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 emulate 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); } |
The body of a loop must not be a semicolon [4 points each, 2% max]
Never write
while(condition);Do not use a bare semicolon as the body of any type of loop. |
Code that is done at the end of the loop should be written after the loop. [4 points each, 2% max]
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 [6 points each, 3% max]
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 [6 points each, 3% max]
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 [4 points each, 1% max]
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. |
Where sensible, a for-loop heading should control one variable [5 points each, 2% max]
Loop
for(int k = 2; k <= n; p = p * x) { k++; }does some of the control of k in the loop heading and some in the body. Instead, put all of the control of k in the loop heading. for(int k = 2; k <= n; k++) { p = p * x; } |