VDM-10 Language Manual

Chapter 3. Data Type Definitions
(a div e) * e ≡ 6
3.1.3 The Character Type
The character type contains all the single character elements of the VDM character set (see Table
B.1 on page 200).
Name: Char
Symbol: char
Values: ’a’, ’b’, . . . , ’1’, ’2’, . . . ’+’, ’-’ . . .
Operators: Assume that c1 and c2 in the following denote arbitrary characters:
Examples:
Operator Name Type
c1 = c2 Equal char * char → bool
c1 c2 Not equal char * char → bool
’a’ = ’b’ ≡ false
’1’ = ’c’ ≡ false
’d’ ’7’ ≡ true
’e’ = ’e’ ≡ true
3.1.4 The Quote Type
The quote type corresponds to enumerated types in a programming language like Pascal. However,
instead of writing the different quote literals between curly brackets in VDM it is done by letting a
quote type consist of a single quote literal and then let them be a part of a union type.
Name: Quote
Symbol: e.g.
Values: , , , . . .
Operators: Assume that q and r in the following denote arbitrary quote values belonging to an
enumerated type T:
Operator Name Type
q = r Equal T * T → bool
q r Not equal T * T → bool
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