How to get the type of a variable in a macro?

I'm currently using this code for a foreach macro:

#define foreach(T, arr, it) for(T::iterator it = (arr).begin(), itend = (arr).end(); it != itend; ++it)

How can i get rid of the first parameter T and make the compiler 开发者_运维技巧figure out which type it should copy/paste in the code T::iterator ? It seems rather silly i need to type it myself when it could be figured out from the variable itself.

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Since this is pre auto and decltype, your best bet is using Eric Niebler's FOREACH macro.

Or upgrade your compiler to VC 2010 and just use auto.

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If you're using a compiler capable of C++11 you can use auto:

#define foreach(arr, it) for(auto it = (arr).begin(), itend = (arr).end(); it != itend; ++it)