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[Frama-c-discuss] question about hybrid logic functions

BAUDIN Patrick wrote:
> Just a minor correction
>   
>> //@ logic type abstract_stack;
>>
>> struct stack {
>>   //@ ghost abstract_stack my_abstraction;
>> } st;
>>
>> /*@ axiomatic A {
>>   @    logic integer count_of{L} (Stack s) reads s.my_abstraction;
>>   @*/
>>   
>>     
> The label {L} isn't used into the reads definition of count_of (it's a 
> meaning of a good abstraction).
>
>   
Wrong. To make things clearer, I should have written

  reads \at(s.my_abstraction,L)

but as said in ACSL manual, when there is only one label in the context, 
the \at can omitted.

>> /*@ requires 0 < count_of{Here}(st);
>>   @ assigns st.my_abstraction;
>>   @ ensures  count_of{Here}(st) == count_of{Old}(st) - 1;
>>   @*/
>>   
>>     
> so, the specification shoud be corrected as follow:
>
>  /*@ requires 0 < count_of{Here}(st);
>   @ assigns st.my_abstraction;
>   @ ensures  count_of{Here}(st) == count_of{Old}(\old(st)) - 1;
>   @*/ 
>
> in fact, the labels {Here} and {Old} given to count_of are insignificant
>   
Wrong again. It is the \old(st) which is useless: st is not modified by 
the function so \old(st)==st.
In the other hand, count_of{Old}(st) is a priori different from 
count_of{Here}(st) since count_of
 reads st.my_abstraction and this is said to be assigned.
> Patrick.
>
>   


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