VDM-10 Language Manual

Chapter 8
Bindings
Syntax: bind = set bind | type bind ;
set bind = pattern, ‘in set’, expression ;
type bind = pattern, ‘:’, type ;
bind list = multiple bind, { ‘,’, multiple bind } ;
multiple bind = multiple set bind
| multiple type bind ;
multiple set bind = pattern list, ‘in set’, expression ;
multiple type bind = pattern list, ‘:’, type ;
Semantics: A bind matches a pattern to a value. In a set bind the value is chosen from the set
defined by the set expression of the bind. In a type bind the value is chosen from the type
defined by the type expression. Multiple bind is the same as bind except that several patterns
are bound to the same set or type. Notice that type binds cannot be executed by the interpreter.
This would require the interpreter to search through infinite domains like the natural
numbers.
Examples: Bindings are mainly used in quantified expressions and comprehensions which can be
seen from these examples:
✞
forall i, j in set inds list & i < j => list(i) 2 }
{ y | y: nat & y > 3 }
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