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Scripts - User defined functions

Function

Function myfunc([param1,param2,...]) declares a function named myfunc that optionally accepts inputs param1,param2,...

The function may optionally return a value. See Return statement below.

  • All variables defined and used in the function are local to the function. They cannot be used in the main body of the script. A variable var used in a function will have other values than a variable with the same name outside the function. This behavior can be changed with the Global function described below.
  • A function cannot be defined within another function (nested functions are not allowed).
  • After you have defined a function you can also use it in the MedCalc spreadsheet. But you have to execute the script containing the function first. Autoloading a script that contains your favorite functions could be useful.

Recursion

A function can call itself (recursion). However the number of recursions is limited to about 500.

The following code will result in an error "[Error: Function recursion too deep]" after about 500 iterations:

function plusone(var) {
	var=var+1;
	print var; println;
	plusone(var);
}
plusone(0);	

You can control the number of recursions, for example as follows:

function plusone(var) {
	var=var+1;
	print var; println;
	if (var<500) { plusone(var); }
}
plusone(0);	

Or you can count the number of iterations using a global variable (see below for the Global variables function):

iterations=0;

function plusone(var) {
	global(iterations); // make iterations global
	var=var+1;
	print var; println;
	iterations++;
	if (iterations>99) { return; }	
	plusone(var);
}

plusone(0);	
print ("iterations ",iterations,"\n");

Return statement

A return statement ends a function and, optionally, returns a value.

function calcbmi(height,weight) {
	bmi=weight/square(height);
	return bmi;
}
mybmi = calcbmi(1.76,70);
print ("My BMI is ",mybmi:1);

Forward declaration

A function can only call other functions that already have been defined. If you have more than one function, and they must call each other, you must forward-declare the function.

The following code results in an error because funcTwo is undefined when it is used in the body of funcOne.

function funcOne(var) {
	if (var>100) { return var; }
	return funcTwo(var*2);
}

function funcTwo(var) {
	return funcOne(var+1);
}

v=funcOne(1);
?v;

This problem is solved by a forward declaration of funcTwo, as follows:

function funcTwo(var);

function funcOne(var) {
	if (var>100) { return var; }
	return funcTwo(var*2);
}

function funcTwo(var) {
	return funcOne(var+1);
}

v=funcOne(1);
?v;

Global variables function

The Global(variable1[,variable2) function marks the listed variables used in the function as global. These variables, when defined outside the function body, can also be used in the function; or when these values are defined in the function, they can also be used in the main body of the script.

See also