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Aucb.370 fa.editor-p utcsrgv!utzoo!decvax!ucbvax!CAD:ARPAVAX:C70:editor-people Thu Feb 4 14:53:23 1982 Undo questions >From CSD.HANSEN@SU-SCORE Thu Feb 4 14:51:03 1982 I have several questions concerning an undo facility in a screen editor and would like to get some opinions.

Is an undo facility absolutely necessary? Would you consider using an editor which had absolutely NO undo capabilities? Should an editor allow you to undo ANYTHING? (Including reads and writes to files?) Or should the capability extend only to such things as undeleting/unkilling? How about getting rid of text just inserted? Probably global changes, such as a global replace/substitute?

Should an undo facility toggle between states? Should an undo be able to undo an undo? Or would it be better to allow a multi-level undo/redo facility in which a user may march back in time to previous stages in the editing session, then march forward again? If this were allowed, how many levels would be appropriate? An interesting problem arises if this were allowed: If you marched back 4 levels, then starting inserting text, would the last 4 changes to the file then be lost? The worst thing you could do at that point would be to start making changes without going forward again.

Tony Hansen Csd.Hansen @ Su-Score houxs!hansen @ Usenet -------

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