LR parser

Types of LR Parser

• LR Parser– SLR(1) or LR(0)– CLR or LR(1)– LALR

Construct LR parser for given grammer

• E->E+T

• E->T

• T->T*F

• T->F

• F->(E)

• F->id

• Take first production rule in Io state

• Then if rule A->a.Bb is a rule and B->c/d is production then then add B->.c , B->.d in closure.

• In I4 state don’t expand E->.T because I2 have same one.No need to apply it.

I1

I2

I3

I4

I5

CLR or LR(1)

• S->CC

• C->aC

• C->d

• In first production add $ as its canonical collection.

• If production is [A->aBb, a1] & if there is production

B->.b1,c then add

B->.b1,c

c belongs to First(b a1)

Here S’->.S null,$

so first (null $) is $ that’s why

S->.CC,$

Here C->.aC

So first (C)={a,d}

first(C $)={a,d} that’s why

C->.aC,a/d

No need to expand I3 =goto(I3,a)

LALR CLR