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Derive the string “abb” for leftmost and rightmost derivation
Problem
Let’s consider a grammar to derive “abb” string using LMD and RMD
S->AB/ ε
A-> aB
B-> Sb
Solution
We have to use context free grammar.
Derivation is a sequence of production rules, which is used to get input strings.
During parsing, we have to take two decisions, which are as follows −
- We have to decide which non-terminal has to be replaced.
- We have to decide which non-terminal has to be replaced by using which production rule.
There are two options to decide which non-terminal has to be replaced with production rule −
- Leftmost derivation
- Rightmost derivation
Leftmost derivation
The input is scanned and replaced with production rules from left to right.
The given production rules are:
S->AB/ ε
A-> aB
B-> Sb
Let’s derive the string “abb” using LMD
S->AB
->aBB {A->aB}
->aSbB {B->Sb}
->abB {S-> ε}
->abSb {B->Sb}
->abb {S-> ε}
Which is our final stringRightmost derivation
The input is scanned and replaced with a production rule from right to left.
The given production rules are:
S->AB/ ε
A-> aB
B-> Sb
Let’s derive the string “abb” using RMD
S -> AB
->ASb {B->Sb}
->Ab {S-> ε}
->aBb {A->aB}
->aSbb {B->Sb}
->abb {S-> ε}
Reached our final string
Updated on: 12-Jun-2021
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