| Even if it is what you intend to write, do not use an assignment as the test in an if, while, do or for statement. If you ask for warnings (which you always should), g++ will warn you about this. |
The body of an if-statement must not be a semicolon [5 points each, 2% max]
Never write
if(condition);Also, never write else; |
Do not have special cases where they are not needed.
For example, the following computes the maximum of
two integers.
int maximum(int x, int y)
{
if(x == y)
{
return x;
}
else if(y > x)
{
return y;
}
else
{
return x;
}
}
The special case for x = y
is not needed. The function works perfectly
well without it. So get rid of it.
|
Do not duplicate code at the beginning or end in the bodies of an if-statement [2 points for each duplicated line, 2% max]
Do not write an if-statement such as
if(condition)
{
x = 1;
...
return 0;
}
else
{
x = 1;
...
return 0;
}
Pull out the common parts, as in
x = 1;
if(condition)
{
...
}
else
{
...
}
return 0;
|
| An expression of form a ? b : c should only be used to produce a value that the program uses. |
Instead of
if(x > 0)
{
doSomething();
}
else
{
}
write
if(x > 0)
{
doSomething();
}
|
Do not use an if-statement with an empty statement preceding else [4 points each, 1% max]
Instead of
if(x > 0)
{
}
else
{
doSomething();
}
write
if(x <= 0)
{
doSomething();
}
A loop body should not have the form
if(...)
{
continue;
}
else
{
...
}
Statement continue; says to do the next iteration of the loop. But that is
what the program would normally do at the end of the loop body.
|
Do not use conditions that are always true or always false [6 points each, 3% max]
Do not use an if-statement whose condition
is always true or always false, except strictly
for debugging or code-checking purposes. For example, if
at a particular place it is not possible for
i and k to have the same value, then
do not say
if(i == k)
{
...
}
|
Do not use redundant tests in if-statements [6 points each, 3% max]
The else part of an if-statement is done if the
condition being tested is false. Do not test
whether it is false. For example,
if(x > 0)
{
step1();
}
else if(x <= 0)
{
step2();
}
should be replaced by
if(x > 0)
{
step1();
}
else
{
step2();
}
|
If code is only performed by one branch of an if-statement, then it must be written inside that branch [4 points each, 2% max]
Look at the following function definition.
int demo(int x)
{
int y;
if(x > 0)
{
y = x + 1;
}
else
{
return -x;
}
return y;
}
Notice that statement return y can only be performed when
x > 0. Moving it into the if-statement yields
int demo(int x)
{
int y;
if(x > 0)
{
y = x + 1;
return y;
}
else
{
return -x;
}
}
A better form is
int demo(int x)
{
if(x > 0)
{
return x + 1;
}
else
{
return -x;
}
}
|
Only use boolean operations on boolean values [4 points each, 1% max]
| Boolean operations (!, && and ||) should only be used on boolean values (which are known to be 0 or 1). Do not use them on integers, pointers, etc. (But see the exception in the next entry.) |
|
The condition in an if-statement, while-statement,
for-statement, do-statement, or any other construct
that performs a yes/no test should be a boolean value.
It should not be a number or a pointer.
An exception is an expression that uses the ctype library, such as isdigit((unsigned) c) and isalpha((unsigned) c). Those can be used in tests as boolean values. |
| Each case in a switch statement must logically end on a break statement or a return statement. (That means the case body must either perform a break or a return in all cases, not that the break or return must physically be the last statement.) You cannot let one case fall into the next. However, you are allowed to have multiple case labels that share a single block of code. |