> One initiative which is interesting is Worlds which could function as a kind of "exploratory programmer's undo." This has been covered in various papers on the VPRI writings page, and touched upon IIRC in some of the NSF updates. It's actually IMHO one of the unsung heroes of what these people have been up to.
My coworker actually delivered a system with "programmer's undo;" it was called a reversible debugger in 1993--before IDEs were popular. We had a virtual machine. There wasn't a lot of syntax present. We used icons instead of just text to represent the program. We could delete operations before and after the program counter. We weren't given enough time to develop it into a full OO system...we kind of got in trouble for competing with industry at the time. Here's a link to the paper. If you have any questions, ask. All primitives were strings, but we did have a simple desktop calculator. http://w3.isis.vanderbilt.edu/OOPSLA2K1/Papers/Carlson.pdf In essence my understanding of how it worked was for every action stepped through an a undo record was created and kept on a stack. I am not sure how undos were handled inside loops, but I suspect there was undo until you find a record for the action present in the program. It was a fine piece of work by Jeffrey Allen. So I'm singing for Jeffrey. The project gave me respect for what you can do with a few desktop gadgets integrated with a flowchart. Programs were exportable and importable to/from C++ global variables--yes, i did the housepainting. We were storing the programs in flat files as well...one per class. If we could combine windows 8 with a reversible debugger, Wow! So now I'm essentially retired and reliving glory days. Remember this is before the web for the initial development.
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