Redundant code

Notable categories of redundant code include: ; Recomputing: Recomputing a value that has previously been calculated and is still available. ; Dead code: Code that is executed but has no external effect (i.e., does not change the output produced by a program). ; Unreachable code: Code that is never executed (also called dead code). ; NOP padding: A NOP instruction might be considered redundant if it is for padding. But if the NOP is required for proper functionality, then it is not redundant. ; Unused identifier: Something declared, but never referenced, is a redundant declaration. ==Examples==

In the following C code, the second x * 2 expression is redundant code. Line 2 can be removed, or alternatively, line 3 can be changed to . int foo(int x) { int y = x * 2; return x * 2; } A more subtle example involves the C preprocessor that inserts code before compilation. Consider: • define min(A,B) ((A) After preprocessing, the code expands to code that evaluates both and twice. To eliminate the duplicate code, the macro could be converted to a function. int shorter_magnitude(int a, int b, int c, int d) { return sqrt(((a*a + b*b) ==See also==