Constants

Constants are a way of giving a name to shared, static values inside of a module or script. In Move, constants are declared using the const keyword.

The constant's must be known at compilation. The constant's value is stored in the compiled module or script. And each time the constant is used, a new copy of that value is made.

Syntax:

const <NAME>: <TYPE> = <EXPRESSION>;

module my_addrx::Constants
{
    use std::debug::print;

    //Some Examples
    const X:u64=10;
    const Y:address=@my_addrx;
    const Z:bool=false;

    fun constants()
    {
        print(&X);
        print(&Y);
        print(&Z);
        
    }

    #[test]
    fun testing()
    {
        constants();
    }
}

Naming:

Constants must start with a capital letter A to Z. After the first letter, constant names can contain underscores _, letters a to z, letters A to Z, or digits 0 to 9.

//Valid
const Foo:u64=123;
const Flag:bool=true; 
const My_Addrx:address=@my_addrx;

//Invalid;
const x:u8=10;
const flag:bool=false;
const my_addrx:address=@my_addrx;

Some other important points:

• Constants are limited to the primitive types bool, u8, u16, u32, u64, u128, u256, address, and vector<u8>.

• Constant names should be upper camel case and begin with an E if they represent error codes (e.g., EIndexOutOfBounds) and upper snake case if they represent a non-error value (e.g., MIN_STAKE).

• public constants are not currently supported. const values can be used only in the declaring module.

• Constant value cannot be accessed outside its module or script scope.