| Your parser backtracking from a bool when it tried to parse an int is VALID behavior. Your parser tries to parse text into several possible types at runtime. Backtracking is STILL valid state. You’re not thinking clearly. Look at my auto pilot example. You have a bug in your program you don’t know about. Altitude reads -9999 meters your heading and direction is reading at the speed of light. Your program sees these values and recognizes invalid state. There is a BUG in your program. Your program WAS never designed to go here. You want to try to recover your autopilot program? How the fuck are you gonna do that? You don’t even know where the bug is. Does your recovery routine involve patching and debugging? Or are you gonna let your autopilot keep operating the plane with those nonsense values? That autopilot might hit the wind breaks to try to slow down the plane and end up crashing the thing. You don’t recover this. You restart the program and pray it doesn’t hit that state again then when you are on the ground you debug it. >>> The thing with functional programming (specifically, immutable data,) is that as long as the invalid state is immutable, you can just back up to some previous caller, and they can figure out whether to deal with it or whether to reject up the its previous caller. This makes no fucking sense. Where the hell will you back up to? Your error came from somewhere but you don’t know where. Return an error value in the child function the parent function receives the error and returns an error itself and this keeps going until you bubble up to the main function because you don’t know where that error came from. Now you have an error in the main function. Wtf are you gonna do? How do you handle an error in the main function that you have no idea where it came from? Here’s an idea. You have the main function restart the program loop. See a similarity here? It’s called crashing and restarting the program. Same effect! This isn’t a functional programming versus non functional thing. It’s a concept that you’re not seeing. |