On 28/10/16 17:03, Makarius wrote:
BTW, there is strictly speaking no need to use fix/assume/show, since
show if/for is already possible, although relatively rarely used.

I use show/if/for regularly in my work (just look at the AFP entry MFMC_Countable to see a few examples), but fix/assume/show is more convenient if the proof needs intermediate "have" steps between the "assume" and the "show". The show/if/for pattern is possible in this case, but I'd have to open another "proof - have ... show ?thesis ... qed" block, which introduces clutter and unnecessary indentation.

Also, if there are several goals with the same assumptions, fix/assume/show/show/show/... is more concise than having to repeat the assumptions for every show (if each goal needs a different proof method invocation).

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