VDM-10 Language Manual

VDM-10 Language Manual
If cycles statements are nested, the outermost one takes precedence and the remainder are
ignored. For instance
✞
✡✝
cycles(3000)(
n := 1;
while n < 10 do
cycles(1000) n := n + 1;
)
The outer cycles statement takes precedence, so assuming this is not executed in the context
of an enclosing cycles statement, the interpreter would increment its internal clock by the
time it takes to process 3000 instructions on the given CPU when executing this statement.
Note that nesting can occur due to operation calls. Consider the following example:
✞
op1 : nat ==> nat
op1(m) ==
cycles (2000) return m + 1;
✆
✡✝
op2 : () ==> nat
op2() ==
(dcl n : nat := 3;
cycles(1000) n := op1(1);
return n)
✆
When executing op2, if the call to op1 is executed, the cycles statement in op1 will be
overridden by the cycles statement in the environment of the call. Thus in op2 following
execution of the statement n := op1(1); the internal clock is incremented by the time it
takes to process 1000 instructions on the given CPU only.
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