To perform SLR parsing, take grammar as input and do the following:
1. Find LR(0) items.
2. Completing the closure.
3. Compute goto(I,X), where, I is set of items and X is grammar symbol.

**CONSTRUCTING SLR(1) PARSING TABLE**

To perform SLR parsing, take grammar as input and do
the following:

1.
Find LR(0) items.

2. Completing
the closure.

3. Compute
goto(I,X), where, I is set of items and X is grammar symbol.

**LR(0) items:**

An LR(0) item of a
grammar G is a production of G with a dot at some position of the right side.
For example, production A → XYZ yields the four items :

A→.XYZ

A
→ X . YZ

A
→ XY . Z

A
→ XYZ .

**Closure operation:**

If I is a set of items
for a grammar G, then closure(I) is the set of items constructed from I by the
two rules:

1.
Initially, every item in I is added to
closure(I).

2.
If A → α . Bβ is in closure(I) and B → γ
is a production, then add the item B → . γ to I , if it

is not already there. We apply this rule until no
more new items can be added to closure(I).

**Goto operation:**

Goto(I, X) is defined
to be the closure of the set of all items [A→ αX . β] such that [A→ α . Xβ] is
in I.

Steps to construct SLR parsing table for grammar G
are:

1.
Augment G and produce G’

2. Construct
the canonical collection of set of items C for G’

3. Construct
the parsing action function action and goto using the following algorithm that
requires FOLLOW(A) for each non-terminal of grammar.

**Algorithm for construction of SLR
parsing table:**

Input : An augmented grammar G’

Output : The SLR parsing table functions action and
goto for G’

Method :

1. Construct
C = {I0, I1, …. In}, the collection of sets of LR(0) items for G’.

2. State
i is constructed from Ii.. The parsing functions for state i are determined as
follows:

(a) If
[A→α∙aβ] is in Ii and goto(Ii,a) = Ij, then set action[i,a] to “shift j”. Here
a must be

terminal.

(b) If
[A→α∙] is in Ii , then set action[i,a] to “reduce A→α” for all a in FOLLOW(A).

(c)
If [S’→S.] is in Ii, then set
action[i,$] to “accept”.

If any conflicting
actions are generated by the above rules, we say grammar is not SLR(1). 3. The
goto transitions for state i are constructed for all non-term

If
goto(Ii,A) = Ij, then goto[i,A] = j.

4.
All entries not defined by rules (2) and
(3) are made “error”

5.
The initial state of the parser is the
one constructed from the [S’→.S].

Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail

**Related Topics **

Copyright © 2018-2021 BrainKart.com; All Rights Reserved. (BS) Developed by Therithal info, Chennai.