How to define a macro that takes arguments?

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. To invoke a macro that takes arguments, you write the name of…

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 argument list?

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. Here are some silly examples using min :

Do you have to balance parentheses in a macro?

Parentheses within each argument must balance; a comma within such parentheses does not end the argument. However, there is no requirement for square brackets or braces to balance, and they do not prevent a comma from separating arguments. Thus, passes two arguments to macro: array [x = y and x + 1].

3.3 Macro 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.

When to use a macro in a program?

From the above program we can see that whenever the compiler finds AREA (l, b) in the program it replaces it with the macros defination i.e., (l*b). The values passed to the macro template AREA (l, b) will also be replaced by the statement (l*b). Therefore, AREA (10, 5) will be equal to 10*5 .

How are macros the same as function calls?

Function-like Macro: These macros are the same as a function call. It replaces the entire code instead of a function name. Pair of parentheses immediately after the macro name is necessary. If we put a space between the macro name and the parentheses in the macro definition then the macro will not work.

Can a macro be left out of the preprocessor?

How does the randomize statement in VBA work?

Using Randomize with the same value for number does not repeat the previous sequence. This example uses the Randomize statement to initialize the random-number generator. Because the number argument has been omitted, Randomize uses the return value from the Timer function as the new seed value.

What happens if you omit number in randomize statement?

If you omit number, the value returned by the system timer is used as the new seed value. If Randomize is not used, the Rnd function (with no arguments) uses the same number as a seed the first time it is called, and thereafter uses the last generated number as a seed value.

Are there any optional parameters for C + + macros?

So to answer your question: no, those features don’t exist for macros. Your only option is to define multiple macros with different names (or not use macros at all). As a sidenote: In C++ it’s generally considered good practice to move away from macros as much as possible.

When to use COMMAS to mark optional arguments?

When you omit one or more optional arguments in the argument list, you use successive commas to mark their positions. The following example call supplies the first and fourth arguments but not the second or third: The following example makes several calls to the MsgBox function.

What happens when the body of a macro is expanded?

When the macro is expanded, each use of a parameter in its body is replaced by the tokens of the corresponding argument. (You need not use all of the parameters in the macro body.) As an example, here is a macro that computes the minimum of two numeric values, as it is defined in many C programs, and some uses.

How is whitespace reduced in a macro argument?

Leading and trailing whitespace in each argument is dropped, and all whitespace between the tokens of an argument is reduced to a single space. Parentheses within each argument must balance; a comma within such parentheses does not end the argument.

What can cause problems with a C macro?

What can cause problems is when the macro body makes use of an identifier that isn’t a formal parameter name, but that identifier also appears in the expansion of a formal parameter. For instance, if you rewrote your MIN macro using the GNU extensions that let you avoid evaluating arguments twice…

What are some examples of macros having odd effects?

Macros can have odd effects if their arguments perform side-effects. For example, Square (++x) expands to ( (++x)* (++x)); if x starts out equal to 1, this expression may evaluate to any of 2, 6, or 9 depending on when the ++ operators are evaluated, and will definitely leave 3 in x instead of the 2 the programmer probably expects.

How to pass multiple arguments to procedure in VBA?

I am trying to pass two string parameters to a Sub, but its not allowing me do that. The approach I have used is given below. While calling callByvalue, it’s throwing a compiler error. Also remember in VBA, When you say Dim s1, s2 As String only s2 will be declared as String and the first one will be declared as Variant

How to define a variadic macro in C99?

Variable-length argument lists C99 added variadic macros that may have a variable number of arguments; these are mostly useful for dealing with variadic functions (like printf) that also take a variable number of arguments. To define a variadic macro, define a macro with arguments where the last argument is three periods: .

Is it recommended to use macros in programming?

This question does not recommend anybody to use macros. This question is not about programming style. The internal representation of the macro will be something like this, where spaces indicate token boundaries, and #1 and #2 are magic internal-use-only tokens indicating where parameters are to be substituted:

How to define a macro that takes arguments?