Redundant code
Redundant code is a computer programming term for code that computes a result that has been previously computed and is currently available, thus the repeated computation of the result is redundant.[1] If redundant code can be identified then it can be eliminated, reducing the overall computational cost of the program.
Example
int f (int x)
{
int y=x*2;
return x*2;
}
The second x*2 expression is redundant code and can be replaced by a reference to the variable y. Alternatively the definition int y=x*2 can instead be removed.
Alternate uses of the term
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The term redundant code may also be used to described code that has any form of redundancy, such as recomputing a value that has previously been calculated and is still available, code that is never executed, or a result which is executed and not used. Redundant code may also be used to refer to code that is executed but has no effect on the output of a program – however this is usually known as dead code. A NOP might be considered to be redundant code that has been explicitly inserted to pad out the instruction stream or introduce a time delay. Identifiers that are declared but never referenced are usually termed as redundant declarations.