yacc/lex or hand-coding?

Question

I am working on new programming language, but I was always puzzled by the fact that everyone is using yaxx/lex to parse the code, but I am not.

My compiler (which is already working) is handcoded in C++/STL, and I cannot say it's complex or took too much time. It has both some kind of lexer and parser, but they are not autogenerated.

Earlier, I wrote a C compiler(not full spec) the same way - it was able to compile the program in 1 pass, with all these back references resolving & preprocessing - this is definitely impossible with yacc/lex.

I just cannot convince myself to scrap all this, and start diving into yaxx/lex - which might need quite an effort to implement and might possibly introduce some grammar limitations.

Is there something I miss when not using yacc/lex? Do I do an evil thing?

Answer 1

The main advantages of using any kind of lexer/parser generator is that it gives you a lot more flexibility if your language evolves. In a hand-coded lexer/parser (especially if you've mixed in a lot of functionality in a single pass!), changes to the language get nasty fairly quickly, whereas with a parser generator you make the change, re-run the generator, and move on with your life. There are certainly no inherent technical limitations to always just writing everything by hand, but I think the evolvability and maintainability of automating away the boring bits is worth it!