Some of these things (like compilers) are often optional modules on CS courses. I think it's difficult to practice programming for very long without figuring ou

Some of these things (like compilers) are often optional modules on CS courses. I think it's difficult to practice programming for very long without figuring out different data structures and recursion , sorting etc. You may also run into compiler problems when you need to do anything complicated with text, at this point playing around with a PEG for a while can get you quite far and is reasonably intuitive. OTOH you are more likely to lack the formal underpinnings and math behind it. Then again, how many people would be able to pass a drilling on Big O/Theta analysis 10 years after completing their degree?