Re: [isabelle] Number of undos

Am 30.09.14 um 15:58 schrieb Makarius:
Using Emacs myself over 15 years, I never understood its way of undo or undo-undo.

A -edit-> B -edit-> C -undo-> B -edit-> D -undo-> B (*) -undo-> A
(*) no way to get back to C from here


A -edit-> B -edit-> C -undo-> B -edit-> D -undo-> B -undo-> C -undo-> B -undo-> ...

There is an edit stack with an undo pointer, each edit command sets the undo pointer to the latest element except the undo command which is an edit command that decrements the undo pointer and reverts the command pointed to by the undo pointer.

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