VDM-10 Language Manual

Chapter 6. Expressions
Examples: The define expression is used in a pragmatic way, in order to make the reader aware of
the fact that the value of the expression depends upon the global variable.
This can be illustrated by a small example:
✞
✡✝
def user = lib(copy)
in
if user =
then true
else false
where copy is defined in the context, lib is global variable (thus lib(copy) can be
considered as looking up the contents of a part of the variable).
The operation GroupRunnerUp expl in section 13.1 also gives an example of a define
expression.
✆
6.3 Unary and Binary Expressions
Syntax: expression = . . .
| unary expression
| binary expression
| . . . ;
unary expression = prefix expression
| map inverse ;
prefix expression = unary operator, expression ;
unary operator = ‘+’ | ‘-’ | ‘abs’ | ‘floor’ | ‘not’ | ‘reverse’
| ‘card’ | ‘power’ | ‘dunion’ | ‘dinter’
| ‘hd’ | ‘tl’ | ‘len’ | ‘elems’ | ‘inds’ | ‘conc’
| ‘dom’ | ‘rng’ | ‘merge’ ;
map inverse = ‘inverse’, expression ;
binary expression = expression, binary operator, expression ;
binary operator = ‘+’ | ‘-’ | ‘*’ | ‘/’
| ‘rem’ | ‘div’ | ‘mod’ | ‘**’
| ‘union’ | ‘inter’ | ‘\’ | ‘subset’
| ‘psubset’ | ‘in set’ | ‘not in set’
| ‘ˆ’
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