Hints for yacc

Some useful hints for using yacc:

• Avoid ``empty'' productions; these are likely to generate grammar conflicts that may be hard to find. Each production should consume some input.

• Follow the Pascal grammar flowcharts exactly. If you just write the grammar from your memory of Pascal syntax, it probably won't work.

• When the action code for a production is called, all of the $i variables have been completely processed and have values.

• If you need to process a list of items of the same kind, the code for begin is a good model.

• The yacc stack has a single type; for our program, that type is TOKEN. If you want to return something else (e.g. a SYMBOL), package it in a TOKEN as symtype.