Re-run a portion of a script

Question

While *run me* will re-run a script from its beginning, is there any way to re-run a portion of a script from a specific line or command?

Answer 1

well, thanks for the star, but I don't see any need to close the conversation just quite yet.
you have a (more or less normal) confusion about what it is, exactly, that a computer does. Computers execute; they don't think. A computer program is just a long series of mathematical operations that are executed sequentially; It will continue to do that until it reaches the end of the calculation or reaches a calculation that can't be performed. It's a programmer's job to anticipate and control all the possible states that the calculation might be in, and to decide what commands get executed in which conditions. it's just like if you're doing math on a hand calculator - if you're doing something that needs trigonometry, then you need to anticipate that you'll need a table of trigonometric values (or a subroutine that calculates trigonometric values, which is basically what the sin and cos keys on your average calculator are), and you get to choose when you use it. the calculator won't do either of those things for you. Programming artifices like loops, conditionals, and subroutines are for the programmer, not the computer - they get used the same way a mathematician will use a ∑ symbol instead of writing out a (possibly infinite) list of things to sum.
if you're writing code that requires user input, then you (the programmer) have to decide what inputs are allowable and what aren't, and you have to create structures that exclude and re-request improper input. if you want something more open ended (or you want something artificial-intelligency that "learns") you need to create structures that keep the the state of the program within a bounded set of states that are functionally executable. You as a programmer have to anticipate and exclude possible undesirable states. If you need to do a long series of calculations to determine whether a user input is proper, then you should set that series in a handler of its own, with proper error checking, and just loop through the request for data and a call to the handler until you have an input that you know you can use. everything you leave to chance is an opening for your program to crash (and remember, a program "crashing" just means that the program didn't do what you expected - it happily made precisely the set of calculations you told it to, and has no idea that it's not doing the right thing).