## Preprocessor Macro Operator

Use the ## operator according to the following rules:

• The ## operator cannot be the very first or very last item in the replacement list of a macro definition.
• The last token of the item in front of the ## operator is concatenated with first token of the item following the ## operator.
• Concatenation takes place before any macros in arguments are expanded.
• If the result of a concatenation is a valid macro name, it is available for further replacement even if it appears in a context in which it would not normally be available.
• If more than one ## operator and/or # operator appears in the replacement list of a macro definition, the order of evaluation of the operators is not defined.

The following examples demonstrate the use of the ## operator:

Preprocessor Directives
Preprocessor Macros

Preprocessor Macro Operators
#define Preprocessor Directive