The syntax of WhyML programs changed in release 1.0. The table in Figure A.1 summarizes the changes.
Note also that logical symbols can no longer be used in non-ghost code; in particular, there is no polymorphic equality in programs anymore, so equality functions must be declared/defined on a per-type basis (already done for type int in the standard library). The CHANGES.md file describes other potential sources of incompatibility.
version 0.88 version 1.0 function f ... let function f ... if called in programs ’L: label L in at x ’L x at L \x. e fun x -> e use HighOrd nothing, not needed anymore HighOrd.pred ty ty -> bool type t model ... type t = abstract ... abstract e ensures { Q } begin ensures { Q } e end namespace N scope N use import M use M "attribute" [@attribute] meta M prop P meta M lemma P or meta M axiom P or meta M goal P loop ... end while true do ... done type ... invariant { ... self.foo ... } type ... invariant { ... foo ... }
Here are a few more semantic changes
diverges
clause to that
function’s contract. It was also possible to disable that warning by
adding the label "W:diverges:N"
to the function’s
name. Version 1.00 of Why3 is more aggressively requiring the user
to prove the termination of functions which are not given the
diverges
clause, and the previous warning is now an
error. The possibility of proving only partial correctness is now
given on a more fine-grain basis: any expression for which one wants
to prove partial correctness only, must by annotated with the
attribute [@vc:divergent]
.In other words, if one was using the following structure in Why3 0.xx:
let f "W:diverges:N" <parameters> <contract> = <body> |
then in 1.00 it should be written as
let f <parameters> <contract> = [@vc:divergent] <body> |
any
construct
in Why3 0.xx was introducing an arbitrary value satisfying the
associated post-condition. In some sense, this construct was
introducing some form of an axiom stating that such a value
exists. In Why3 1.00, it is now mandatory to prove the existence of
such a value, and a VC is generated for that purpose.To obtain the effect of the former semantics of the any
construct, one should use instead a local val
function. In other words, if one was using the following structure in Why3 0.xx:
any t ensures { P } |
then in 1.00 it should be written as
val x:t ensures { P } in x |
The syntax of WhyML programs changed in release 0.80. The table in Figure A.2 summarizes the changes.
version 0.73 version 0.80 type t = {| field : int |} type t = { field : int } {| field = 5 |} { field = 5 } use import module M use import M let rec f (x:int) (y:int) : t
variant { t } with rel =
{ P }
e
{ Q }
| Exc1 -> { R1 }
| Exc2 n -> { R2 }let rec f (x:int) (y:int) : t
variant { t with rel }
requires { P }
ensures { Q }
raises { Exc1 -> R1
| Exc2 n -> R2 }
= eval f (x:int) (y:int) :
{ P }
t
writes a b
{ Q }
| Exc1 -> { R1 }
| Exc2 n -> { R2 }val f (x:int) (y:int) : t
requires { P }
writes { a, b }
ensures { Q }
raises { Exc1 -> R1
| Exc2 n -> R2 }val f : x:int -> y:int ->
{ P }
t
writes a b
{ Q }
| Exc1 -> { R1 }
| Exc2 n -> { R2 }val f (x y:int) : t
requires { P }
writes { a, b }
ensures { Q }
raises { Exc1 -> R1
| Exc2 n -> R2 }abstract e { Q } abstract e ensures { Q }
The main new features with respect to Why 2.xx are the following.