References - Manhunter07/MFL GitHub Wiki

References are pointer values that address either a variable, function or type. Their value can be a reference to either a declared variable, a declared function, a declared type or an anonymous function.

Unassignd references are represented by the special value of Nil. Such cannot be de-referenced: de-referencing an unassigned reference causes an exception.

Syntactically, references are created in three different ways:

• References to declared (named) addressable objects (like variables) are created using the @ symbol in front of the identifier:

  @MyVar
  @System.TypeOf
  @RoundRange
  

  This procedure is called addresing and is the most common way of creating a reference.
• References to anonymous functions are created using the func-ret statement:

  func A, B ret A + B
  func |S|: string(256) ret -S
  func X, N: Number = 1 ret X ^ N
  

• References to anonymous types are created using the @ symbol in front of a type constructor:

  @string
  @enum(Null, True)
  @record(X, Y, Z)
  

In addition to that, there exist a few special functions that return references, like ConstructorOf that returns a reference to the constructor of a given type, passed by reference.

See also: Operators#References

Operator	Operation
?	Signus

The signus of a reference is 0 for unassigned references (Nil) or 1 otherwise.

Operator	Operation
?	Comparison
?=	Equality

First operand	Second operand	Result
Nil	Nil	0
Nil	Not Nil	-1
Not Nil	Nil	1
Not Nil	Not Nil	0

The comparison (?) of two references returns the comparison result of their signuses. This is 0 for two identical operands, -1 if only the first operand is unassigned (Nil) or 1 if only the second operand is unassigned (Nil).

Like any other data type, references support the type compatibility check operator (?:). It returns True on supported reference types, but also any other type that supports the respected value(s).

• System.ReferenceType