Global procedures

Once you define a global procedure, you can call it anywhere: from any script file, within any function, or from the command line. The general form of a global procedure declaration is:

global proc return_type procedure_name ( arguments ) { 

	MEL_statements 

}

• the global keyword makes the new procedure available everywhere.
• The proc keyword indicates you are defining a procedure.
• After proc you can add a keyword for the return type of the procedure. For example, if the procedure returns an integer, type int. If the procedure does not return a value, you can leave this out.
• The name of the procedure.
• A list of arguments in brackets, separated by commas. Each argument is a variable name (with the $ at the beginning) preceded by its type (for example string).
• A block of code to execute when you call the procedure.

Return values

If you specify a return type for a procedure, then you must use a return operator somewhere in the procedure’s code block to return a value.

global proc float square(float $x) {

	return $x * $x;

}

square(5.0);

25

If you don’t specify a return type for a procedure (indicating that the procedure will not return a value), then you can only specify the return operator without a return value. Use of a return operator in this context serves as a function break.

// This does not work. 

global proc add5(int $x) {return $x+5;}; 

// Error: global proc cc(int $x) {return $x+5;}; // 

// Error: This procedure has no return value. //

// This works. 

global proc add5(int $x) {return;};" 

Examples

Here are some example procedure declarations:

global proc string sayHi() {

	return "Hello!\n");

}

global proc float square(float $x) {

	return $x * $x;

}

global proc int max(int $a, int $b) {

	if ($a > $b) {

		return $a;

	} else {

		return $b;

}

global proc msg() {

	print "This proc has no return value.\n";

}

Local procedures

If you leave the global keyword off the beginning of a procedure declaration, the procedure is local to the file in which it is defined.

// This is a local procedure

// that is only visible to the code in this file.

proc red5() {print("red5 standing by...\n");}

This is very useful for making “helper” procedures that do work for other procedures. You can expose just one or two global procedures, hiding the helper code from other people using your scripts.

You cannot define a local procedure in the Script Editor. They are only available in external script files.