Debugging

If its possible to step through a program is it possible to step back in a program?

no

yes

Time travelling debuggers.

An implementation can keep a log of all state changes. One would only need to know the previous value occupied in whatever was overwritten when the instruction executed. This would require the program to take memory linear in the amount of time it ran for though. One could instead only keep track of the previous N instructions, rather than everything since the program started running.

EXPERT CONTINUATIONS

or just have undo operations for all operations, but since most operations are destructive, that ain't gonna work.

>>1
Yes, Microsoft­­® Visual Studio™ 2010 has this functionality.

>>6
bitches dont know bout my billiard ball computer
http://en.wikipedia.org/wiki/Billiard_ball_computer

>>7

no it doesn't. If the filthy piece of shit can't produce a non corrupted stack trace, then how can it reverse execute code, hmmm? hmmmm??

GDB has this feature since 2009.
http://sourceware.org/gdb/wiki/ReverseDebug
http://www.gnu.org/s/gdb/news/reversible.html

>>1
is it possible to step back in a program?
http://en.wikipedia.org/wiki/Reversible_logic

If its possible to step through a program is it possible to step back in a program?
If can use such feature to implement undo in a text editor and for backtracking, without using additional memory.

>>8

If powered with flubber, then this will be able to perform super tasks!

If its possible, then you can use
self fix.

>>9
no it doesn't. If the filthy piece of shit can't produce a non corrupted stack trace, then how can it reverse execute code, hmmm? hmmmm??
Transfer $10 to my PayPal, www.paypal.com/users/FairXTheHaxxor and I'll teach you how to use Google to find answers to questions like that!

>>1
Some debuggers support logging, and with good enough logging, you can reconstruct/roll-back operations. There was at least one such experimental debugger/logger for Bochs out there. The actual memory/disk requirements tend to be pretty high unfortunately, but what would you expect?

Not entirely sure how common it would be for high-level languages, but it might be possible to keep the history a lot more compact. Purely fuctional languages (such as Haskell) might not even need a log at all as at the high-level description there is no state at all.

>>16
OCaml's debugger has time travel too. I'm not sure how they handle it since OCaml has state. How would Haskell does with FFI under the debugger?