How to insert macro arguments into variables C++ processor?

Question

I would like to pass arguments into variables names using the macros.

For example, I would have this code :

#define FOO(I,J) double varIJiable

FOO(1,2);

And the preprocessor would output this :

double var12iable;

out of curiosity: Why do you want to do this? If you have to type FOO(1,2); every single time you want to spell out the variable name, how is that better than writing double var12iable; in the first place? — 463035818_is_not_an_ai
– 463035818_is_not_an_ai, Commented Mar 12, 2020 at 12:57
I'm learning instruction level parallelism, so I'll have a bunch of double var00iable; double var01iable; double var10iable;...It it just to have a template so that I spend less time coding. — truvaking
– truvaking, Commented Mar 12, 2020 at 13:00
For easier searching, the ## operator is commonly called the "token pasting operator". — Fred Larson
– Fred Larson, Commented Mar 12, 2020 at 13:01
@truvaking it might cause less time coding but more time debugging. Being explicit is always good. — calynr
– calynr, Commented Mar 12, 2020 at 13:04

Rene · Accepted Answer · 2020-03-12 12:57:28Z

6

Use the ## operator to concatenate strings through the pre-processor

#define FOO(I,J) double var ## I ## J ## iable

answered Mar 12, 2020 at 12:57

Rene

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