VDM-10 Language Manual

VDM-10 Language Manual
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types
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ExpertId = token;
Expert :: expertid : ExpertId
quali : set of Qualification
inv ex == ex.quali {};
Qualification = | | |
functions
QualificationOK: set of Expert * Qualification -> bool
QualificationOK(exs,reqquali) ==
exists ex in set exs & reqquali in set ex.quali
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The function min gives us an example of a universal quantification:
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min(s: set of nat) x: nat
pre s {}
post x in set s and
forall y in set s \ {x} & y < x
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We can use unique existential quantification to state the functional property satisfied by all
maps m:
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forall d in set dom m &
exists1 r in set rng m & m(d) = r
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6.6 The Iota Expression
Syntax: expression = . . .
| iota expression
| . . . ;
iota expression = ‘iota’, bind, ‘&’, expression ;
Semantics: An iota expression has the form:
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iota bd & e
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