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3.4 Special Types and Type Constructors

3.4.2 Closure Types

The type of a closure is described using the following syntax:

closure_type	::=	"&" "(" [arg_types] ")" [type_decl]
(The syntax of arg_types is specified along with signatures in section 3.3.4.)

A closure type of the form

&(t1,...,tN):tR
describes a closure whose eval method has the signature:

signature eval(&(t1,...,tN):tR, t1, ..., tN):tR
Closure types are related by implicit subtyping rules that reflect standard contravariant subtyping: a closure type of the form &(t1,...,tN):tR is a subtype of a closure type of the form &(s1,...,sN):sR iff each ti is a supertype of the corresponding si and tR is a subtype of sR.

The Cecil Language: Specification and Rationale, Version 2.1 - 25 MARCH 1997
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