VDM-10 Language Manual

Chapter 6. Expressions
where all the domain expressions di and range expressions ri are general expressions. The
empty map must be written as {|->}.
A map comprehension has the form:
✞
✡✝
{ed |-> er | mbd1, ..., mbdn & P}
where constructs mbd1, ..., mbdn are multiple bindings of variables from the expressions
ed and er to sets (or types). The map comprehension constructs a mapping by evaluating
the expressions ed and er on all the possible bindings for which the predicate P
evaluates to true.
✆
Examples: Given that GroupG is equal to the map
✞
✡✝
{ |-> mk_(2,1,0), |-> mk_(2,0,1),
|-> mk_(1,0,2), |-> mk_(0,1,2) }
✆
then:
{ t |-> let mk (w,d,-) = GroupG(t)
in w * 3 + d
| t in set dom GroupG}
{ t |-> w * 3 + d
| t in set dom GroupG, w,d,l:nat
& mk (w,d,l) = GroupG(t)
and w > l}
≡ { |-> 7,
|-> 6,
|-> 3,
|-> 1}
≡ { |-> 7,
|-> 6}
6.10 Tuple Constructor Expressions
Syntax: expression = . . .
| tuple constructor
| . . . ;
tuple constructor = ‘mk ’, ‘(’, expression, ‘,’, expression list, ‘)’ ;
Semantics: The tuple constructor expression has the form:
✞
mk_(e1, e2, ..., en)
✡✝
✆
where ei is a general expression. It can only be used by the equality and inequality operators.
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