Bottom up parser

Question 1

what is the difference between top down parser and bottom up parser ?

Answer 1

S –> Ab
top-down parser :
pop S into the stack then the right-hand side
left most derivation

bottom-up parser
pop the Ab then the left-hand side(S)
right-most derivation

Question 2

bottom-up parser action :

Answer 2

reduce :
A -> Ba replacing the eight hand side by A
| a | | A |
| B | ==> | . |
|__ | |__|
shift :
reads the terminal from the input and put it on the stack

Question 3

what are possible conflicts we can face

Answer 3

Reduce Reduce problem :
| A | and two rules B -> A / C -> Ab the parser gets
| b | stuck which rule he should reduce
|__ |
Shift reduce conflict: it gets stuck whether it keeps shifting or reducing

Question 4

viable prefix

Answer 4

the prefix of a right sentential for that that occur during a successfull right-most derivation

Question 5

how to extract viable prefix in a given automata

Answer 5

the prefix of a right sentential for that that occur during a successful run of the bottom parser, and can be extracted during the build of CFSM

Question 6

LR 0 parser rules

Answer 6

at all the time we want a viable prefix on the stack
associate a config to each state of CFSM
at each step, we run CFGM on the stack content
Associate actions to each CFGM state A-> a. reduce otherwise, shift

Question 7

what is the unrealistic things about LR 0 parser

Answer 7

the fact that we need to feed the content of stack CFSM, however, it can be treated through inserting the state number

Question 8

what are the limitations of LR0?

Answer 8

it can lead to conflicts

Question 9

SLR 1

Answer 9

it’s