Question

5. (4 marks) Use left-factoring and/or eliminate left-recursion to transform each of the below eight grammars into a form where the immediate problems preventing the use of recursive- descent parsing have been removed. As usual capital letters denote variables and lower case letters are terminals. (f) $S \rightarrow SB \mid \varepsilon$ $B \rightarrow Bb \mid a$ (g) $S \rightarrow Sba \mid Sbcd \mid \varepsilon$ (h) $S \rightarrow Sdb \mid Sdc \mid a \mid c$ Hint for (g) and (h): Here after elimination of left recursion you need to use also left- factoring (or vice versa).

          5. (4 marks) Use left-factoring and/or eliminate left-recursion to transform each of the below
eight grammars into a form where the immediate problems preventing the use of recursive-
descent parsing have been removed. As usual capital letters denote variables and lower
case letters are terminals.
(f) $S \rightarrow SB \mid \varepsilon$
$B \rightarrow Bb \mid a$
(g) $S \rightarrow Sba \mid Sbcd \mid \varepsilon$
(h) $S \rightarrow Sdb \mid Sdc \mid a \mid c$
Hint for (g) and (h): Here after elimination of left recursion you need to use also left-
factoring (or vice versa).

5. (4 marks) Use left-factoring and/or eliminate left-recursion to transform each of the below
eight grammars into a form where the immediate problems preventing the use of recursive-
descent parsing have been removed. As usual capital letters denote variables and lower
case letters are terminals.
(f) S → SB |ε
B → Bb | a
(g) S → Sba | Sbcd |ε
(h) S → Sdb | Sdc | a | c
Hint for (g) and (h): Here after elimination of left recursion you need to use also left-
factoring (or vice versa).

Added by Frank I.

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