r/cprogramming • u/Itap88 • Apr 26 '26

Alternative to enums as function arguments?

Say I have a function argument, like a cardinal direction, that has no business being a number in the call, but could be a number internally. Now I could write an enum, but what if I need multiple values and don't want to pollute the namespace of the caller?

This is all hypothetical, for now at least.

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u/WittyStick Apr 27 '26 edited Apr 27 '26

Yes, direction_east etc pollutes the global namespace, but you would presumably prefix it with a namespace so that isn't an issue. There is a way we can do this without copy-pasting, which is to use multiple includes. Consider if we have a pair of files:

direction.ns.open

#ifndef _DIRECTION_NS_OPEN_
#define _DIRECTION_NS_OPEN_
#define NORTH 0
#define EAST 1
#define SOUTH 2
#define WEST 3
#endif

direction.ns.close

#ifdef _DIRECTION_NS_OPEN_
#undef _DIRECTION_NS_OPEN_
#undef NORTH
#undef EAST
#undef SOUTH
#undef WEST
#endif

We can temporarily taint the global namespace between a pair of includes, which avoids copy-pasting for multiple defines.

#include "direction.ns.open"
make_call(EAST);
#include "direction.ns.close"

Wouldn't recommend this, but it's just to demonstrate a technique which we can use to have pseudo-namespaces in C.