Looking these things up, Chomsky normal form is clearly irrelevant, and Greibach normal form forces "progress" to be made. The equivalent of this is, let's say

Looking these things up, Chomsky normal form is clearly irrelevant, and Greibach normal form forces "progress" to be made. The equivalent of this is, let's say you hand-roll a parser and notice that it's recursing infinitely. Then you realize, "Durr, you bozo, you need to force it to consume something or it'll recurse forever without going anywhere!" And then you solve that problem by having it consume something first. For example, if you're parsing an expression a+b*c+d, and thanks to some naive thinking about left-associative operators, it recursively calls itself without consuming data. So you'll say, okay, first I need to chew off something that consumes data. Then -- what else can you do -- see if you've got an operator, and grow an expression from there. That's a well-contained situation that marches you straight into the right solution.