VDM-10 Language Manual

Chapter 17. Top-level Specification (VDM-SL)
✞
✡✝
name renamed new_name
✆
where name is the name of the imported construct, and new name is the new name for the
construct. This way, more meaningful names can be given to constructs. Note that in the
importing module it is not possible to refer to DefModule‘name (where DefModule is
the name of the defining module) any longer but only to newname.
It is possible to include type information in the imports section, such that this information
will only be used by the static semantics check of the complete module. If no type information
is given, the static semantics can also find this information in the exporting module (see
section 19).
When a type which has been exported with the struct keyword (with its structure) is
imported the importing module may only make use of this structure if it repeats the type
definition from the exporting module in its type import. In case such a type is a composite
type and it is also renamed this has the consequence that the tag is renamed as well.
Examples: We can model an ATM card as consisting of a card number and an expiry date. This
requires the digit type defined in the module BankAccount. It also uses the function
digval from the same module.
✞
module ATMCard
imports
from BankAccount types digit
functions digval renamed atmc_digval
exports all
definitions
types
digit = BankAccount‘digit;
atmc:: cardnumber : seq1 of digit
expiry : digit * digit * digit * digit
inv mk_atmc(cardnumber, mk_(m1,m2,-,-)) ==
atmc_digval(m1) * 10 + atmc_digval(m2) = 8
functions
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