VDM-10 Language Manual

Chapter 13
Statements
In this section the different kind of statements will be described one by one. Each of them will be
described by means of:
• A syntax description in BNF.
• An informal semantics description.
• An example illustrating its usage.
13.1 Let Statements
Syntax:
statement = let statement
| let be statement
| . . . ;
let statement = ‘let’, local definition, { ‘,’, local definition },
‘in’, statement ;
let be statement = ‘let’, multiple bind, [ ‘be’, ‘st’, expression ], ‘in’,
statement ;
local definition = value definition
| function definition ;
value definition = pattern, [ ‘:’, type ], ‘=’, expression ;
where the “function definition” component is described in section 5.
Semantics: The let statement and the let-be-such-that statement are similar to the corresponding
let and let-be-such-that expressions except that the in part is a statement instead of an
expression. Thus it can be explained as follows:
A simple let statement has the form:
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