On 12-11-20 06:54 AM, citb@lavabit.com wrote:
I know nothing about compilers and interpreters. I checked several books, but none of them explained why we have to translate a high-level language into a small (core) language. Is it impossible (very hard) to directly translate high-level language into machine code?
Let the overall distance be fixed. More steps over that same distance means each step is smaller, easier to design, easier to understand, easier to correct if there are mistakes. Forget code generation. Just parse and validate and then discard. Already there are like 4 steps. Translate character sequence into token sequence. Translate token sequence into grammar tree, while checking grammar. Translate grammar tree into declaration groups, identifier lookup tables, etc., while checking whether every used identifier is declared or imported. Translate those groups and tables into type-annotated groups and tables, while checking types. Whew! After 4 steps of translating this to that, we still haven't reached the core language! Why? Because... have you ever tried to write a type-checker for character sequence? I'm sure some mad genius can do it, but I don't want to be that mad genius.