I was doing compiler design back in the late 70s/early 80s and writing your own compiler generator was quite common at the time - it wasn't until things like bi

I was doing compiler design back in the late 70s/early 80s and writing your own compiler generator was quite common at the time - it wasn't until things like bison/yacc became available which not only did an excellent job but also allowed one to hack on them and/or the result (for example my Algol68 compiler needed to be able to be able to decide how to resolve some shift/reduce conflicts on the fly ... that's how you do changeable operator precedence)