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Functions

A function is a group of statements that is executed when it is called from some point of the program. The following is its format:

Source code (UnigineScript)
type name(parameter1, parameter2, ...) {
	// statements 
}

The example of function usage:

Source code (UnigineScript)
int foo(int a,int b) {
	return a + b;
}

int sum;
sum = foo(3,4); // 'sum' is 7

You can define only a function prototype before using it:

Source code (UnigineScript)
int foo(int a,int b);
foo(5,2);

int foo(int a,int b) {
	return a + b;
}

All functions are in the global scope.

Returning a Value#

void#

void function represents absence of a variable and is used as a return value in functions that don't return anything.

Source code (UnigineScript)
// this function doesn't return anything
	void func() {
	log.message("func is called\n");
}

Return Values#

Values are returned with the help of an optional return statement. Any data type may be returned, except for vector, map,and enum.

Functions with the void return type always return 0.

Parameter Passing Mechanism#

Passing Arguments by Reference#

By default, function arguments are passed by value, so, if you change the value of the argument within the function, it does not affect anything outside of the function. If you wish to allow a function to modify its arguments, you must pass them by reference.

If you want an argument to a function to be always passed by reference, mark it with an ampersand (&) in the function definition.

Source code (UnigineScript)
void foo(int &a,int b) {
	a = 13; // it will affect the variable outside since 'a' is passed as a reference
	b = 14;
}

int a = -1;
int b = 20;
foo(a,b);
log.message("%d %d\n",a,b);

// the result is: "13 20"

Containers and class instances are always passed by reference. For example:

Source code (UnigineScript)
class Foo {
	int v;
};

void foo(int &v) {
	if(v) log.message("%d ",v);
	v = 13;
}

Foo f = new Foo();
foo(f.v);
foo(f.v);

int v[] = (0);
foo(v[0]);
foo(v[0]);

Foo f1[] = (new Foo());
foo(f1[0].v);
foo(f1[0].v);

//the output is: 13 13 13

Passing Containers as Arguments#

To pass a vector or a map as an argument, use a proper function declaration, as shown below:

Source code (UnigineScript)
void foo(int a[]) {
	a[13] = 321;
}

int arr[] = ( 1, 2, 3, 4 );
foo(arr);

Accessing Elements of the Function#

The function return value elements can be accessed as follows:

Source code (UnigineScript)
vec3 foo() { return vec3(1.0,2.0,3.0); }
log.message("%f %f\n",foo().x,foo()[0]); // the result is: 1 1
log.message("%f %f\n",translate(1.0,2.0,3.0).m23,translate(1.0,2.0,3.0)[14]); // the result is: 3 3

Note that if the returned value is a class, you need to cast it to its own type.

Source code (UnigineScript)
class Bar {
	string toString() {
		return "bar";
    }
};

Bar bar() { return new Bar() };
log.message("%s\n",Bar(bar()).toString());

Default Argument Values#

You can provide default values for function arguments. After that, if you leave an argument empty, its default value will be used. The omitted argument can be indicated with a comma (no whitespace required).

Source code (UnigineScript)
void foo(int a = 1,int b = 2) {
	log.message("%d %d\n",a,b);
}

foo(); // the result is: 1 2
foo(3,4); // the result is: 3 4
foo(3); // the result is: 3 2
foo(,4); // the result is: 1 4

Technique of Using Functions#

Function Overloading#

You can read about function overloading here.

Using Inline Functions#

Functions of the following signature and body will be automatically inlined, which gives a noticeable speed boost for user-defined classes:

Source code (UnigineScript)
void get() { return a; }
void set(int b) { a = b; }
void get(int i) { return a[i]; }
void set(int i,int b) { a[i] = b; }

__FUNC__#

The __FUNC__ preprocessor constant always reports the right function. It never effect performance in any way.

Source code (UnigineScript)
// __FUNC__ == function signature

class MyClass {
	int doSomethingWithNode(Node node) {
		if(node == NULL) {
			log.error("%s: node is NULL\n",__FUNC__);
		}
  
    }

};

// Output: MyClass::doSomethingWithNode(): node is NULL

Using Anonymous Functions#

Anonymous functions are used to create functions that have no name. They are useful if you need to call a short function or a function that is not used elsewhere in the code (and therefore, its name is not important). The anonymous functions are declared in the style of C++ syntax:

Source code (UnigineScript)
[]() { log.message("hello!\n");

Declaration of the anonymous function (the []() {}; construction) always returns its identifier.

Notice
The function itself can return any value.
So, the anonymous function can be declared and passed as an argument to a function that receives a function identifier, for example:
  • To one of the run() functions of the Async class (see the data/samples/systems/socket_3 sample).
  • To the call() container function:
    Source code (UnigineScript)
    int a[0];
    // append 2 anonymous functions to the array 
    a.append([](int a) { log.message("array callback 0 %d\n",a); });
    a.append([](int a) { log.message("array callback 1 %d\n",a); });
    // call all the functions stored in the array 
    a.call(1);
    
    // Output:
    // array callback 0 1
    // array callback 1 1
  • To the call() control statement:
    Source code (UnigineScript)
    call([]() { log.message("foo\n"); });
    call([](int a) { printf("foo %d\n",a); },1);
    
    // Output: 
    // foo
    // foo 1
    Source code (UnigineScript)
    int f = []() { log.message("callback\n"); };
    call(f);
    
    // Output: callback
Last update: 2019-08-16