VDM-10 Language Manual

VDM-10 Language Manual
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public logEnvToSys: nat ==> ()
logEnvToSys (pev) == e2s := e2s munion {pev |-> time};
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6.24 Literals and Names
Syntax: expression = . . .
| name
| old name
| symbolic literal
| . . . ;
name = identifier, [ ‘‘’, identifier ] ;
name list = name, { ‘,’, name } ;
old name = identifier, ‘˜’ ;
Semantics: Names and old names are used to access definitions of functions, operations, values
and state components. A name has the form:
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id1‘id2
where id1 and id2 are simple identifiers. If a name consists of only one identifier, the
identifier is defined within scope, i.e. it is defined either locally as a pattern identifier or
variable, or globally within the current module as a function, operation, value or global
variable. Otherwise, the identifier id1 indicates the module/class name where the construct
is defined (see also section 17 and section 14.2 and appendix B.)
An old name is used to access the old value of global variables in the post condition of an
operation definition (see section 12) and in the post condition of specification statements (see
section 13.15). It has the form:
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id˜
where id is a state component.
Symbolic literals are constant values of some basic type.
Examples: Names and symbolic literals are used throughout all examples in this document (see
appendix B.2).
For an example of the use of old names, consider the VDM-SL state defined as:
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