I'm working on a school project that requires me to parse a BNF grammar. I'm a little confused as to what role the pipe character (|) - which I believe means "or" - plays in a rule.
For example, if I had the following:
<a> ::= b c d | e f g
Which of the terminals is the | applied to? Using parentheses for grouping, which would describe how the "or" is applied?
(b c d) | (e f g)
(b c) (d) | (e) (f g)
Is the | applied to the entire set of terminals, or just the two next to the |?
And what if I had a set up like:
<a> ::= b | <c> <d>
<b> ::= e | f
<c> ::= g | h
Would it still be true if <c> and <d> refer to non-terminals? To what would the | be applied in this case?
In general,
rule := a b c | d e f
is grouped as
rule := (a b c) | (d e f)
This doesn't change whether or not you apply them to terminals or non-terminals.