Felix provides three simple forms to define and initialise variables. The var binder is used to define a variable, it binds a name to a storage location.
Variables with type and initialiser¶
A variable can be defined with a type annotation and an initialiser.
var b : bool = true; var i : int = 1; var s : string = "Hello"; var d : double = 4.2; var f : float = 4.2f;
The specified type must agree with the type of the initialiser.
Variables without type annotation¶
A variable can also be defined without a type annotation provided it has an initialiser.
var b = true; var i = 1; var s = "Hello"; var d = 4.2; var f = 4.2f;
In these cases the type of the variable is the type of the initialiser.
Variables without initialiser¶
Variables can be defined without an initialiser.
var b : bool; var i : int; var s : string; var d : double; var f : float;
In this case the variable will be initialised by the underlying C++ default initialiser. It is an error to specify a variable this way if the underlying C++ type does not have a default initialiser.
If the underlying C++ default initialiser is trivial, so that the store is not modified, then the Felix variable is uninitialised.
An assignment can be used to assign the first value stored in the location of a variable, to modify the value which an explicit initialiser previously provided, or to modify the value which the underlying C++ default initialiser provided.
var b : bool; var i = 1; b = true; i = 2;
Assignments are executed when control flows through the assignment.
Var binders are equivalent to declaration of an uninitialised variable and an assignment. The location of the declaration within the current scope is not relevant. The position of an initialising assignment is. For example:
a = 1; var b = a; var a : int;
is equivalent to
var a = 1; var b = a;