VDM-10 Language Manual

VDM-10 Language Manual
| ‘++’ | ‘munion’ | ‘’
| ‘and’ | ‘or’
| ‘=>’ | ‘’ | ‘=’ | ‘’
| ‘=’
| ‘comp’ ;
Semantics: Unary and binary expressions are a combination of operands and operators denoting
a value of a specific type. The signature of all these operators is already given in section 3,
so no further explanation will be provided here. The map inverse unary operator is treated
separately because it is written with postfix notation in the mathematical syntax.
Examples: Examples using these operators were given in section 3, so none will be provided here.
6.4 Conditional Expressions
Syntax: expression = . . .
| if expression
| cases expression
| . . . ;
if expression = ‘if’, expression, ‘then’, expression,
{ elseif expression }, ‘else’, expression ;
elseif expression = ‘elseif’, expression, ‘then’, expression ;
cases expression = ‘cases’, expression, ‘:’,
cases expression alternatives,
[ ‘,’, others expression ], ‘end’ ;
cases expression alternatives =
cases expression alternative,
{ ‘,’, cases expression alternative } ;
cases expression alternative = pattern list, ‘->’, expression ;
others expression = ‘others’, ‘->’, expression ;
Semantics: If expressions and cases expressions allow the choice of one from a number of expressions
on the basis of the value of a particular expression.
The if expression has the form:
✞
✡✝
if e1
then e2
else e3
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✆