The following is a grammar for regular expressions over symbols a and b only, using + in place of 1 for union, to avoid conflict with the use of vertical bar as a metasymbol in grammars:
a) Left factor this grammar.
b) Does left factoring make the grammar suitable for top-down parsing?
c) In addition to left factoring, eliminate left recursion from the original
d) Is the resulting grammar suitable for top-down parsing?