Operators

rascal-0.40.17

Synopsis

The Rascal operators.

Syntax

Some example operators:

Exp + Exp
Exp [ Exp ]
! Exp
Exp in Exp

Description

An operator expression consists of an operator and one or more operands. The evaluation order of the operands depends on the operator. The operator is applied to the operands and the resulting value (or values in some cases) is the result of the operator expression.

All operators are summarized in the following table. They are listed from highest precedence to lowest precedence. In other words, operators listed earlier in the table bind stronger.

Operator	See	Short Description
Exp . Name		Select named field from structured value
	Location fields
	DateTime fields
	Tuple fields
	Relation columns
Exp₁ [ Name = Exp₂ ]	FieldAssignment FieldAssignment FieldAssignment	Change value of named field of structured value
Exp < field₁, ... >	FieldProjection, FieldProjection	Select fields from relation or structured value
Exp is Name		Check if Exp has name Name
	Parse Tree,
	ConcreteSyntax,
	Algebraic Data Type
Exp has Name		Check if a field with Name is present on Exp
	Parse Tree
	ConcreteSyntax
	Algebraic Data Type
Exp₁ [ Exp₂ , Exp₃, .... ]		Project values for given key from list, map, tuple or relation.
	list
	map
	tuple
	relation
Exp₁ [ Exp₂ , Exp₃ .. Exp₄ ]		Retrieve a slice from a list, string, or node.
	list
	string
	node
Exp?	IsDefined	Test whether an expression has a defined value
!Exp	Negation	Negate a Boolean value
- Exp	Negation	Negation of numbers
Exp +		Transitive closure on relation or list relation
	Relation +
	List +
Exp *		Reflexive transitive closure on relation or list relation
	Relation *,
	List *
Exp₁ o Exp₂		Exp₁ and Exp₂ should evaluate to a relation or map; return their composition. Note: the letter "o" is thus a keyword
	relation
	map
Exp₁ / Exp₂	Division	Divide two numbers
Exp₁ % Exp₂	Remainder	Remainder on numbers
Exp₁ * Exp₂		Products
	number	Multiply numbers
	list	Cartesian product on lists
	set	Cartesian product on sets
	relation	Cartesian product on relations
Exp₁ & Exp₂	Intersection
	list intersection
	set intersection
	map intersection
Exp₁ + Exp₂		Sums
	Addition	Add numbers
	Concatenation	Concatenate strings
	Concatenation	Concatenate lists
	Insert Append	Insert and Append list elements
	Concatenation	Concatenate tuples
	Union	Set union
	Union	Map "union"
	AddSegment	Adding path segments to locations
Exp₁ - Exp₂		Subtraction
	numbers	subtraction of numbers
	lists	difference on lists
	sets	set difference
	maps	map difference
Exp₁ join Exp₂	Join Join on relation
Exp₁ in Exp₂		test membership
	list	list membership
	set	set membership
	map	map key membership
Exp₁ notin Exp₂		inverse membership
	list	list membership
	set	set membership
	map	map key membership
Exp₁ <= Exp₂	reflexive less-than
	number	numbers
	string	strings
	location	locations
	datetime	datetime
	list	list
	set	set
	map	map
Exp₁ < Exp₂		irreflexive less-than
	number	numbers
	string	strings
	location	locations
	datetime	datetime
	list	list
	set	set
	map	map
Exp₁ >= Exp₂		reflexive greater-than
	number	numbers
	string	strings
	location	locations
	datetime	datetime
	list	list
	set	set
	map	map
Exp₁ > Exp₂		irreflexive greater-than
	number	numbers
	string	strings
	location	locations
	datetime	datetime
	list	list
	set	set
	map	map
Pat := Exp	Match	Pattern matches value of expression
Pat !:= Exp	NoMatch	Pattern does not match value of expression
Exp₁ == Exp₂		Equality
	numbers
	strings
	locations
	datetime
	lists
	sets
	maps
Exp₁ != Exp₂		Inequality
	numbers
	strings
	locations
	datetime
	lists
	sets
	maps
Exp₁ ? Exp₂	IfDefinedElse	Value of expression when it is defined, otherwise alternative value
Exp₁ ? Exp₂ : Exp₃	Conditional	Conditional expression for all types
Exp₁ ==> Exp₂	Implication	Implication on Boolean values
Exp₁ <==> Exp₂	Equivalence	Equivalence on Boolean values
Exp₁ && Exp₂	And	And on Boolean values
Exp₁ \|\| Exp₂	Or	Or on Boolean values