Mez Files, Units and Functions


Units and Functions

Units are groupings of functions and variables appearing in .mez files. They can be thought of as modules or namespaces. A Helium app must have at least one unit. The unit keyword must be followed by a unique unit name. A unit must have at least one function.


Unit Example
unit MyUnit;
// Other code follows
string myVar;
int factorial(int x) {
    if(x == 0 || x == 1) {
        return 1;
    } else if (x > 1) {
        return factorial(x - 1);
    return 0;



Objects, enums and validators are global, so they can optionally be in a separate source code file without a unit.

Mez File Comments

Two types of comments are supported: single line comments and multi-line comments:

Single Line Comments Example
// date tstamp =;
// decimal rand = System.random();
Multi-line Comments Example
/* date tstamp =;
decimal rand = System.random(); */




Variable and Function Scope

Suppose a unit MyUnit has a unit variable named myVar and a function named factorial. Both have global scope and can be accessed by any function in this or other units, e.g. from TestUnit in the example below. The only time a variable or custom object in the Helium DSL is not globally scoped is when it is declared inside a function and thus scoped to the function alone. To refer to a unit’s member functions or variables from another unit, you have to use the scope operator (the colon).

unit TestUnit;
void test() {
    MyUnit:myVar = "New string value!";
    int f = MyUnit:factorial(5);


 Note: Unit variables cannot be in line initialized when they are declared. The following code will not compile:

unit MyUnit;

string myVar = "some value"; // this is not a legal statement



Additional Mentions and References