The reason you see people using yacc instead of hand coding it is that its really annoying to hand-write a bottom up parser for an LR grammar. If you are going

The reason you see people using yacc instead of hand coding it is that its really annoying to hand-write a bottom up parser for an LR grammar. If you are going to be writing things by hand then its more intuitive to use a top-down recursive-descent parser instead. However, top-down parsing requires more "tricks" to parse usual languages (for example, you need to rewrite the grammar to an equivalent one without left-recursion) so most introductions you see use bottom-up parsing instead.