Conditions should be boolean [Boolean condition: 1-2 points]
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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. |
An if-statement, while-statement, etc. tests whether
its condition is true. Do not write something like
if(isEmpty(x) == true)where you redundantly ask if isEmpty(x) is true. Write if(isEmpty(x))Use ! for negation. Instead of if(isEmpty(x) == false)write if(!isEmpty(x)) |
| 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. |
All statements that are parts of other statements must
be compound statements
(surrounded by braces).
For example, the body of a loop
must be a compound statement. The parts of an if-statement
must be compound statements. For example,
if(x == 0) return 0; else return 2*x + 1;violates this rule. Use
if(x == 0)
{
return 0;
}
else
{
return 2*x + 1;
}
Compound statements must be correctly indented. |
Do not use a ? b : c as a statement [Conditional expression as statement: 1-4 points]
| An expression of form a ? b : c should only be used to produce a value that the program uses. |
Do not write an explicit empty else [Empty else: 1-2 points]
Instead of
if(x > 0)
{
doSomething();
}
else
{
}
write
if(x > 0)
{
doSomething();
}
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Do not use an if-statement with an empty statement preceding else [Empty then: 1-2 points]
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.
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Do not force a boolean expression to be a test where that is not appropriate. [Boolean force: 1 point]
Suppose that E is an expression of type bool. Statement
if(E)
{
return true;
}
else
{
return false;
}
is equivalent to
return E.If it is appropriate to treat a boolean expression in a way similarly to an arithmetic expression (as a value), then do so. It yields simpler and more efficient programs. |
Do not use conditions that are always true or always false [Constant condition: 1-2 points]
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)
{
...
}
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Do not use redundant tests in if-statements [Redundant test: 1-2 points]
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();
}
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If code is only performed by one branch of an if-statement, then it must be written inside that branch [Branch separation: 1 point]
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;
}
}
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