Comment by yomritoyj

I love how notebooks allow the mixing of code and output and support incremental development by letting you choose which cells to execute. But I find the semantics horrible. Each time you execute a cell you do so in an environment that depends on your entire history and cannot be figured out by simply reading the notebook. I wish for a environment which would have the same semantics as a script but which would snapshot the environment at the entry to each cell so that when a cell is modified execution does not have to resume at the beginning. Even better if downstream data dependencies are tracked so that after modifying and reexecuting a cell we know which downstream results have become stale. Does such an environment exist?