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LL(1) PARSER

LL(1) PARSER. Eg:  Consider the following grammar: S --> iEtSS’ | a S’ --> eS | ع E --> b. First Follow S i,a $,e E b t

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LL(1) PARSER

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  1. LL(1) PARSER Eg:Consider the following grammar: S --> iEtSS’ | a S’ --> eS | ع E --> b

  2. First Follow S i,a $,e E b t S’ e,ع $,e

  3. The grammar is ambiguous and it is evident by the fact that we have two entries corresponding to M[S’,e] containing S -->ع and S->eS.This ambiguity can be resolved if we choose S’-->eS i.e associating the else’s with the closest previous “then”. LL(1) grammars have distinct properties.No ambiguous grammar or left recusive grammar can be LL(1).A grammar is LL(1) if and only if whenever a production A--> C | D the following conditions hold: 1)For no terminal a both C and D derive strings beginning with a.Thus First(C) != First(D) 2)At most one of C or D can derive € • 3) If C* ع then D doesnot derive any string beginning with terminal Follow(A).

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