Name Rascal/Statements/Assignment

Synopsis Assign a value to a variable or more complex data structure.

Syntax Assignable AssignmentOp Exp

where AssignmentOp may be one of =, +=, -=, *=, /=, or ?=.

An Assignable is one of the following:

1. Var
2. Assignable [ Exp ]
3. Assignable [ Exp .. Exp ]
4. Assignable [ Exp, Exp .. Exp ]
5. Assignable . Name
6. < Assignable, Assignable, ..., Assignable >
7. Assignable ? Exp
8. Assignable @ Name
9. Name ( Assignable, Assignable, ... )

Details Variable Subscription Slice Field Multiple IsDefined Annotation Constructor

Description The purpose of an assignment is to assign a new value to a simple variable or to an element of a more complex data structure.

The standard assignment operator is =. The other assignment operators can be expressed as abbreviations for the standard assignment operator.

Assignment Operator	Equivalent to
Assignable += Exp	Assignable = Assignable + Exp
Assignable -= Exp	Assignable = Assignable - Exp
Assignable *= Exp	Assignable = Assignable * Exp
Assignable /= Exp	Assignable = Assignable / Exp
Assignable &= Exp	Assignable = Assignable & Exp
Assignable ?= Exp	Assignable = Assignable ? Exp

An assignable is either a single variable, (the base variable), optionally followed by subscriptions, slices or field selections. The assignment statement always results in assigning a completely new value to the base variable. We distinguish the following forms of assignment:

• Variable: Assign to a variable.
• Subscription: Assign a single element of a structured value.
• Slice: Assign to a slice of a list or string.
• Field: Assign to a field of a tuple, relation or datatype.
• Multiple: Assign to multiple assignables.
• IsDefined: Assign but replace if value is not defined.
• Annotation: Assign to annotation.
• Constructor: Assign to constructor.

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