Constants are defined by assigning the value of an expression to a variable (that is, a value name). They are immutable by design, which means that their values cannot be reassigned. Put in another way, they can be assigned once, at their declaration. When defining a constant you can also ascribe a type to it.
Constant declarations are introduced by the keyword
const, like so:
Note that constants cannot be redefined in the same block scope:
However, the following does work: