Basic Compiler Technology
Lexers, Parsers, Code Generators are of all ages (old skool: lex/flex, yacc/bison (modern-ish: PCCTS/ANTLR), burg/lburg/...)
The recursive descent parser works by evaluating the grammar rules in order of precedence, where each function call is a grammar rule match attempt and the first one returning success is a 'grammar rule match' which will allow the parser to continue parsing the input.
Also, the input is assumed to be size limited, i.e. a infinite lookahead grammar is fine with us. (This doesn't work in situations where you need to parse a stream, but that is a problem area that few of us have to deal with in actual reality. Mostly we like limited lookahead grammars becaus