VDM-10 Language Manual

Chapter 13. Statements
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bootSequence : runLevel ==> ()
bootSequence(rl) ==
for all p in set pInit(rl) do
start(p);
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Alternatively we could use the startlist statement here:
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bootSequenceList : runLevel ==> ()
bootSequenceList(rl) ==
startlist(pInit(rl))
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13.15 The Specification Statement
Syntax: statement = . . .
| specification statement ;
specification statement = ‘[’, implicit operation body, ‘]’ ;
Semantics: The specification statement can be used to describe a desired effect a statement in
terms of a pre- and a post-condition. Thus, it captures the abstraction of a statement, permitting
it to have an abstract (implicit) specification without being forced to an operation
definition. The specification statement is equivalent with the body of an implicitly defined
operation (see section 12). Thus specification statements can not be executed.
Examples: We can use a specification statement to specify a bubble maximum part of a bubble
sort:
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Sort2 : () ==> ()
Sort2 () ==
while x < y do
|| (BubbleMin(),
[ext wr l : seq1 of nat
wr y : nat
rd x : nat
pre x < y
post y < y˜ and
permutation(l˜(x,...,y˜),l(x,...,y˜)) and
forall i in set {x,...,y} & l(i) < l(y˜)]
)
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