Compare SLR, CLR, and LALR parsers.

S. no. SLR ParsersCanonical LR ParsersLALR Parsers
1SLR parser are easiest to implement.CLR parsers are difficult to implement.LALR parsers are difficult to implement than SLR parser but less than CLR parsers.
2. SLR parsers make use of canonical collection of LR(0) items for constructing the parsing tables.CLR parsers are uses LR(1) collection of items for constructing the parsing tables part.LALR parsers LR(1) collection , items with items having same core merged into a single itemset.
3SLR parsers don’t do any lookahead i.e., they lookahead zeroCLR parsers lookahead one symbol.LALR parsers lookahead one symbol.
4. SLR parsers are cost effective to construct in terms of time and space.CLR parsers are expensive to construct in terms – of time and space.The cost of constructing LALR parsers is i intermediate between SLR and CLR parser.
5.SLR parsers have hundreds of states.CLR parses have thousands of states.LALR parsers have hundreds of state and is same as number states in SLR parsers.
6.SLR parsers uses FOLLOW information to guide reductions.CLR parsers uses lookahead symbol to guide reductions.LALR parsers uses lookahead symbol to guide reductions.
7.SLR parsers may fail to I produce a table for certain class of grammars on which ether succeed.CLR parser works on very large class of grammar.LALR parser works on very large class grammars.
8.Every SLR(1) grammar is LR(1) grammar and LALR(1).Every LR(1) grammar may not be SLR( 1) grammar.Every LALR(1) grammar may not be SLR(1) but every LALR(1) grammar is LR(1) grammar.
9.A shift-reduce or reduce-reduce conflict may arise in SLR parsing table.A shift-reduce or reduce-reduce conflicted may arise but chances are less than that in SLR parsing tables.A shift-reduce conflict can not arise but a reduce-reduce conflict may arise.
10.SLR parser is least powerful.A CLR parsers is most powerful among the family canonical of bottom-up parsers.A LALR parser is intermediate in power between SLR and LR parser.

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