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Which is better:

#define PI 3.14

or

const double PI = 3.14;

This was an interview question, and I don't seem to find an unambiguous answer.

I suppose I should prefer not to use macros, but I'd like to have a sturdy answer to this.

EDIT: So the question marked duplicate says, that define "don't respect scopes", but I don't really want scopes here, I want something like a super global, PI must be PI everywhere, should be accessed from anywhere. #define seems more reasonable here to me.

Also I don't see where could using PI go wrong in compile time so please provide an example.

Community
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Ferenc Dajka
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  • id argue that it depends on your target platform. more specifically, the way the compiler creates the assembly and the underlying cpu instruction set. Just as a for instance, if you #define a constant double, and the compiler emits it as an immediate value, an instruction might become 2-4 bytes larger than if it simply emitted a reference to a memory location. 2-4 bytes 10000 times adds up to not a whole hell of a lot. BUT if you only have 4kb of code space on your target platform, you might want to do something else. – jhbh Oct 13 '16 at 11:49

1 Answers1

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You would want PI to be constant and be in the scope for as much the app runs so static const PI would be good

Patrice Chaula
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