# Re: [isabelle] Propositions: value vs lemma

```Could you also post the definition of circ1? (Remark: it would be more
standard to use "=" instead of "==".)

cheers

cheers

On 02/20/2013 07:29 AM, Jonathan Balkind wrote:
> Hi there,
>
> I've been trying to formulate a proof based on some functions that I've created and I've become a little confused. While I've tried to search a little through the mailing list for related questions, I had trouble because I'm looking for something involving three common keywords in Isabelle.
>
> Essentially I've got a proposition which I can use the "value" command to evaluate as True, in the form of a proposition. However, when I try making this into a lemma of the same form, I seem to be unable to prove it using any of the proof methods I'm aware of. What approaches does value use to evaluate its argument, and can I apply those methods via apply in proof mode too? Otherwise, could you point me toward what assumption I might be making that could be incorrect? I've also tried nitpick, which showed no counterexamples to this proposition.
>
> value "(circ1 [False, False] [x, y] 2) ≡ [False, False, False]"
> lemma "(circ1 [False, False] [x, y] 2) ≡ [False, False, False]"
>
> I'm probably just making a ridiculous rookie error, so any help here would be much appreciated.
>
> Thanks,
> Jonathan
>

```

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