The Fortress Language Specification - CiteSeerX

11.5 Operator and Identifier Parameters
Syntax:
StaticParam ::= opr Op
| ident Id
Static parameters may include one or more operator symbols and identifiers denoting method names. Syntactically,
an operator parameter begins with the special reserved word opr followed by an operator symbol. An identifier
parameter begins with the special reserved word ident followed by an identifier.
Unlike other static parameters, operator and identifier parameters may be used in both type context and value context.
The following example operator parameter ⊙ :
trait UnaryOperatorT extends UnaryOperatorT, ⊙,opr ⊙
opr ⊙(self): T
end
is declared as a static parameter of UnaryOperator, instantiated as a static argument, and declared as an operator
method.
Operator and identifier parameters may be freely intermixed with other static parameters. For example, the following
trait HasLeftZeroes:
trait HasLeftZeroesT extends HasLeftZeroesT, ⊙,isLeftZero,opr ⊙,ident isLeftZero
extends { BinaryOperatorT, ⊙ }
isLeftZero():Boolean
property ∀(a:T, b: T) a.isLeftZero() →: ((a ⊙ b) = a)
end
is parameterized with a type parameter T , an operator parameter ⊙ , and an identifier parameter isLeftZero . Many
interesting examples are described in Section 37.3.
11.6 Where Clauses
Syntax:
Where ::= where { WhereClauseList }
WhereClauseList ::= WhereClause ( , WhereClause) ∗
WhereClause ::= Id Extends
| TypeAlias
| NatConstranint
| IntConstranint
| BoolConstraint
| UnitConstraint
| TypeRef coerces TypeRef
| TypeRef widens TypeRef
Static parameters may have constraints placed on them in a where clause. A where clause begins with the special
reserved word where , followed by a sequence of static parameter constraints enclosed in braces { and } , and
separated by commas.
A where clause may introduce new static variables, i.e., identifiers for types and other static entities that may not
be static parameters. We use the term where -clause variables to refer to static variables that are not also static
parameters. The where -clause variables must be bound in a where clause.
A static parameter constraint is one of the following forms:
83