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Is there a way to detect an empty macro argument?
In particular, the case that __VA_ARGS__ is empty corresponds exactly to the outcome _ISEMPTY (0, 0, 0, 1). All other outcomes will indicate that it was non-empty. We will detect this case with the following helper macro. and we leave all the other 15 cases undefined.
How to check if a range is empty in VBA?
To check if a range is empty with VBA, use a macro with the following statement structure: Item: If… Then. VBA Construct: Opening statement of If… Then… Else statement. Description: The If… Then… Else statement conditionally executes a group of statements depending on the value of an expression.
Can a narg2 detect an empty argument list?
The macro NARG2 that we introduced in post still has a major disadvantage, it will not be able to detect an empty argument list. This is due to a fundamental difference between C and its preprocessor. For C a parenthesis () is empty and contains no argument.
Which is a function call with an empty argument?
For C an expression like f () is a function call with an empty argument list. For the preprocessor f () is a macro call (if f is defined as such) with one argument, namely the empty token. You see that if you look at f (,): this has two arguments, both empty tokens.
Can a function like a macro take arguments?
Function-like macros can take arguments, just like true functions. To define a macro that uses arguments, you insert parameters between the pair of parentheses in the macro definition that make the macro function-like. The parameters must be valid C identifiers, separated by commas and optionally whitespace.
What do I need to invoke a macro in C?
The parameters must be valid C identifiers, separated by commas and optionally whitespace. To invoke a macro that takes arguments, you write the name of the macro followed by a list of actual arguments in parentheses, separated by commas.
Can a macro be left out of the preprocessor?
You can leave macro arguments empty; this is not an error to the preprocessor (but many macros will then expand to invalid code). You cannot leave out arguments entirely; if a macro takes two arguments, there must be exactly one comma at the top level of its argument list.