2. Non- Recursive Predictive Parsing
• Non-Recursive predictive parsing uses a parsing table that shows
which production rule to select from several alternatives available for
expanding a given non-terminal and the first terminal symbol that
should be produced by that non-terminal.
• The parsing table consists of rows and columns where there are row
for each non-terminal and a column for each terminal symbol
including S, the end marker for the input string.
3. non-recursive parser Components
• This non-recursive parser looks up which product to be applied in a
parsing table. A LL(1) parser has the following components:
• (1) buffer: an input buffer which contains the string to be passed
• (2) stack: a pushdown stack which contains a sequence of grammar symbols
• (3) A parsing table: a 2d array M[A, a]
• where
• A->non-terminal, a->terminal or $
• (4) output stream:
• end of the stack and an end of the input symbols are both denoted with $
4. Algorithm for non recursive Predictive Parsing:
• The main Concept ->With the help of FIRST() and FOLLOW() sets, this
parsing can be done using just a stack that avoids the recursive calls.
• For each rule, A->x in grammar G:
• For each terminal ‘a’ contained in FIRST(A) add A->x to M[A, a] in the parsing
table if x derives ‘a’ as the first symbol.
• If FIRST(A) contains null production for each terminal ‘b’ in FOLLOW(A), add
this production (A->null) to M[A, b] in the parsing table.
6. LR Parser
• LR parsing is one type of bottom up parsing. It is used to parse the
large class of grammars.
• In the LR parsing, "L" stands for left-to-right scanning of the input.
• "R" stands for constructing a right most derivation in reverse.
• "K" is the number of input symbols of the look ahead used to make
number of parsing decision.
7. Types of LR Parser
• LR parsing is divided into four parts: LR (0) parsing, SLR parsing, CLR
parsing and LALR parsing.
8. LR algorithm
• The LR algorithm requires stack, input, output and parsing table. In all
type of LR parsing, input, output and stack are same but parsing table
is different.
9. • Input buffer is used to indicate end of input and it contains the string
to be parsed followed by a $ Symbol.
• A stack is used to contain a sequence of grammar symbols with a $ at
the bottom of the stack.
• Parsing table is a two dimensional array. It contains two parts: Action
part and Go To part.
