I'm trying to use an OCaml program to form an umambiguous protocol
specification.  I've convinced myself that by proper definition of
my types, and avoiding using the _ in matches, I can get OCaml to help
me verify that I have a complete specification.  I'm doing this by
defining a function that specifies the behavior of one of the protocol
partners when it receives a message.  Here is an example of what I
have.<br>
<br>
let requestOp = REQUEST_KEY | SUCCESS;;<br>
<br>
let message = None | Register of requestOp * int;;<br>
<br>
let receive idList msg =<br>
&nbsp; match message with<br>
&nbsp;&nbsp;&nbsp;&nbsp; None -&gt; None<br>
<br>
|&nbsp;&nbsp;&nbsp; Register( REQUEST_KEY, id ) -&gt; begin<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; match idList with <br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; [] -&gt; Register(SUCCESS, id)<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |&nbsp;&nbsp; l when
(List.mem id l) -&gt; Register(Success, (next_available_id l))<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |&nbsp; _ -&gt; Register(Success, id)<br>
;;<br>
<br>
The problem is with the final pattern in the inner match
expression.&nbsp; I'm really trying to avoid using _ in patterns so
that I'm forced to specify an action for each possible case (hence the
reason I'm trying to use OCaml here).&nbsp;&nbsp;&nbsp; It appears that
since I'm using a guard here that OCaml can't, at compile time,
determine whether or not I'm being exhaustive.<br>
<br>
Is there a way to accomplish the same thing as above without using
guards so that OCaml will be able to determine that my match is
exhaustive?<br>
<br>
&nbsp;&nbsp;&nbsp; <br>