On Mon, 15 Jun 2015, Lars Noschinski wrote:

I wonder whether this syntax would be useful for other situations, e.g. assume and assumes, too?

Something like that is in the MKM 2008 paper "Logic-free reasoning in Isabelle/Isar", see http://www4.in.tum.de/~wenzelm/papers/isar-reasoning.pdf


I was thinking about this again when brushing up the internal Isar structures, but did not make any moves in that direction yet, due to the following open questions:

  * What is the meaning of this anyway?

      assume "B x" if "A x" for x

    Is it:

      assume "!!x. A x ==> B x"

    or is it:

      fix x assume "A x" assume "B x"

    Since if/for in have/show is explicit notation for the eigen-context,
    the second one is conceptually more obvious, but probably not to the
    user.

  * What are convicing applications where spelling out !! and ==>
    connectives in assumptions, or extra fix/assume context elements is
    too awkward?

  * Implementation complexity: if/for for assume and presume would demand
    the same for "theorem fixes / assumes / shows / obtains", probably
    also for 'obtain' and 'consider' etc.


        Makarius

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