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Comment by lubutu | Hacker News Reader

Something I would love to have is a debugger for an interpreted language which visualises the program's state as a graph, say, and you can wind time forward and back. Then, as you make changes to the code the visualisation updates according to what the program's state would have been at this point in the program had it been running the updated code. To me that would feel like magic.

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> Something I would love to have is a debugger for an interpreted language which visualises the program's state as a graph, say, and you can wind time forward and back.

see "debugging backwards in time" by Bil Lewis (yes, one "L" in each word.) http://www.lambdacs.com/debugger/AADEBUG_Mar_03.pdf

He gave a talk at google on the subject, it's a great watch: http://video.google.com/videoplay?docid=3897010229726822034

This actually exists in the IDE for Inform7, a DSL for writing interactive fiction (text adventure) games. The feature is called "Skein", and it will graph all your playtests, and highlight in red which ones changed after you change your code. You can see it at 6:20 in this video: http://vimeo.com/4221277

Inform 7 is just awesome in general. The source code reads like English. Here's a code snippet: http://inform7.com/learn/eg/dm/source_14.html

gdb does this: http://sourceware.org/gdb/news/reversible.html, http://sourceware.org/gdb/onlinedocs/gdb/Checkpoint_002fRest... (Linux-only, so I've never used those features.) Slapping a nicer interface on it is left as an exercise to the reader. ;-)

In Python: http://people.csail.mit.edu/pgbovine/python/

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