VDM-10 Language Manual

VDM-10 Language Manual
For VDM-SL call statements are defined as:
call statement = name, ‘(’, [ expression list ], ‘)’ ;
For VDM++ and VDM-RT call statements are defined as:
call statement = [ object designator, ‘.’ ], name,
‘(’, [ expression list ], ‘)’, ;
object designator = name
| self expression
| new expression
| object field reference
| object apply ;
object field reference = object designator, ‘.’, identifier ;
object apply = object designator, ‘(’, [ expression list ], ‘)’ ;
Semantics: In VDM-SL the call statement has the form:
✞
opname(param1, param2, ..., paramn)
✡✝
In VDM++ and VDM-RT the call statement has the form:
✞
object.opname(param1, param2, ..., paramn)
✡✝
✆
✆
The call statement calls an operation, opname, (in a VDM++ and VDM-RT context in an
object, object), and returns the result of evaluating the operation. Because operations can
manipulate global variables a call statement does not necessarily have to return a value as
function calls do.
In VDM++ and VDM-RT if an object designator is specified it must yield an object reference
to an object of a class in which the operation opname is defined, and then the operation
must be specified as public. If no object designator is specified the operation will
be called in the current object. If the operation is defined in a superclass, it must have been
defined as public or protected.
Examples: In VDM-SL the operation ResetStack given below does not have any parameter
and does not return a value whereas the operation PopStack returns the top element of the
stack.
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