Hi,
hard to say, why it does not work without further details. However, one
guess is that types do not match. I would recommend showing the types
when printing the theorem. I expect that P might be of type `'a ->
bool`. In this case you need to instantiate 'a to string first.
Best
Thomas
On 23.07.2018 18:10, Dylan Melville wrote:
> I have a theorem called EX which returns true when a value is an
> element of a list. It is defined as:
>
> thm = |- (EX P [] <=> F) /\ (EX P (CONS h t) <=> P h \/ EX P t)
>
> I am trying to use this theorem with `P` being `(\x. x = “T”)` and `t`
> being a long list of strings which contains “T”. Unfortunately my
> attempts to use INST on this theorem haven’t worked. Why doesn’t the
> following work?
>
> INST [`(\x:string. x = “T")`,`P:(string->bool)`] EX;;
>
> Thank you.
>
> -Dylan Melville (McMaster University)
>
>
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