[Ur] Unification Problems

[Adam Chlipala]

On 10/21/2012 06:41 PM, David Snider wrote:
> My user.urs file has:
>
> val main : unit -> transaction page

Well, I copied your code into a .ur file, gave it a .urs file like the 
above, and changed the [Sha.hash] references to use an identity function 
instead.  It all type-checks for me.  I would need a self-contained 
complete source archive to say anything else.

> On 10/21/2012 06:16 PM, Adam Chlipala wrote:
>> That didn't turn out to be it.  Your [main] function is ambiguous; 
>> it's not obvious from the code there now that it returns standalone 
>> pages.  You can use type annotations in your .ur file to indicate the 
>> type, but it would be better to create a .urs file declaring [main] 
>> as in most of the demos.
>>
>> On 10/21/2012 05:55 PM, David Snider wrote:
>>> Ah, OK...
>>>
>>> Here is the whole source:
>>> http://pastebin.com/EZMqZVkd
>>>
>>> Is it that it can't decide whether to take it from the User table 
>>> record or the cookie record?
>>>
>>> On 10/21/2012 05:42 PM, Adam Chlipala wrote:
>>>> I need more context to give a complete answer.  The error message 
>>>> means that some type is not uniquely determined, and the message 
>>>> will show you where the undetermined type appears.
>>>>
>>>> My first guess, though: Start the function declaration like this:
>>>>     fun checkPassword (r : {Email : string, Password : string}) =
>>>>
>>>> Otherwise, there might be other fields in [r].
>>>>
>>>> On 10/21/2012 05:39 PM, David Snider wrote:
>>>>> What's the correct way of doing this?
>>>>>
>>>>> Error: Some constructor unification variables are undetermined in 
>>>>> declaration
>>>>>
>>>>> cookie userSession : { Email : string, Password : string }
>>>>>
>>>>> ... snip ...
>>>>>
>>>>> fun checkPassword r =
>>>>> let
>>>>>    val cryptPass = {Email=r.Email, Password=Sha.hash r.Password}
>>>>> in
>>>>>    re' <- oneOrNoRows1(SELECT user.Id
>>>>>                         FROM user
>>>>>                        WHERE user.Email = {[cryptPass.Email]}
>>>>>                          AND user.Password = {[cryptPass.Password]});
>>>>>    case re' of
>>>>>       None => return False
>>>>>     | Some re => setCookie userSession { Value = cryptPass, 
>>>>> Expires=None,Secure=False };
>>>>>       return True
>>>>> end
>>>>