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Rewrote final sentence to make its meaning clearer and remove comma overload. |
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The following examples are in [[C (computer language)|C]].
<
int foo(int iX)
{
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return iX*2;
}
</syntaxhighlight>
The second <code>iX*2</code> expression is redundant code and can be replaced by a reference to the variable <code>iY</code>. Alternatively, the definition <code>int iY = iX*2</code> can instead be removed.
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Consider:
<
#define min(A,B) ((A)<(B)?(A):(B))
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return sqrt(min(u1*u1 + v1*v1, u2*u2 + v2*v2));
}
</syntaxhighlight>
As a consequence of using the [[C preprocessor]], the compiler will only see the expanded form:
<
int shorter_magnitude(int u1, int v1, int u2, int v2)
{
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return sqrt(temp);
}
</syntaxhighlight>
Because the use of min/max macros is very common, modern compilers are programmed to recognize and eliminate redundancy caused by their use.
There is no redundancy, however, in the following code:
<
#define max(A,B) ((A)>(B)?(A):(B))
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return max(cutoff, rand()%range);
}
</syntaxhighlight>
If the initial call to rand(), modulo range, is greater than or equal to cutoff, rand() will be called a second time for a second computation of rand()%range, which may result in a value that is actually lower than the cutoff. The max macro thus may not produce the intended behavior for this function.
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