Help with a #define?

[Martin De Kauwe]

Hi,

I am trying to translate some c++ code and have run into an expression
which makes no sense to me? I have a C background so understand the
#define, but not what the use of the double ## means, e.g. x##n?

Any assistance would be much appreciated...

#define NCLIMIT(x,mn,mx) x##n += nclimit (x, x##n, mn, mx)

 

[Ian Collins]

Hi,

I am trying to translate some c++ code and have run into an expression
which makes no sense to me? I have a C background so understand the
#define, but not what the use of the double ## means, e.g. x##n?

Any assistance would be much appreciated...

It's bizarre how often this gets asked, look up concatenation (or even
##) in your trusty copy of K&R. It's also the first item in the index
of The C++ programming language!

 

[Martin De Kauwe]

It's bizarre how often this gets asked, look up concatenation (or even
##) in your trusty copy of K&R.  It's also the first item in the index
of The C++ programming language!

Hi,

thanks as you say it is right there in K&R! I guess instead of looking
in the book I tried googling and well not an easy keyword to find it
seems!

 

[Ian Collins]

Hi,

thanks as you say it is right there in K&R! I guess instead of looking
in the book I tried googling and well not an easy keyword to find it
seems!

You still can't beat the printed word!