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Expr ( ). Expr ( ) E  T E’ E’  + T E’ | ε T  F T’ T’  * F T’ | ε F  ( E ) | id Orig. Grammar LL(1) Grammar E  E + T | T T  T.

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Presentation on theme: "Expr ( ). Expr ( ) E  T E’ E’  + T E’ | ε T  F T’ T’  * F T’ | ε F  ( E ) | id Orig. Grammar LL(1) Grammar E  E + T | T T  T."— Presentation transcript:

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2 Expr ( )

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8 E  T E’ E’  + T E’ | ε T  F T’ T’  * F T’ | ε F  ( E ) | id
Orig. Grammar LL(1) Grammar E  E + T | T T  T * F | F F  ( E ) | id E  T E’ E’  + T E’ | ε T  F T’ T’  * F T’ | ε F  ( E ) | id

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14 Example: E  T E’ E’  + T E’ | ε T  F T’ T’ 
Example: E  T E’ E’  + T E’ | ε T  F T’ T’  * F T’ | ε F  ( E ) | id FIRST E { (, id } E’ { +, ε } T { (, id } T’ { *, ε } F { (, id } FOLLOW E { $, ) } E’ { $, ) } T { +, $, ) } T’ { +, $, ) } F { *, +, $, ) } Question: is this example grammar LL(1)?

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19 else if ℇ ∈ FIRST(s) and curr_tok ∈ FOLLOW(s) then return

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27 E  T E’ E’  + T E’ | ε T  F T’ T’  * F T’ | ε F  ( E ) | id
Example FIRST E { (, id } E’ { +, ε } T { (, id } T’ { *, ε } F { (, id } FOLLOW E { $, ) } E’ { $, ) } T { +, $, ) } T’ { +, $, ) } F { *, +, $, ) } LL(1) Grammar E  T E’ E’  + T E’ | ε T  F T’ T’  * F T’ | ε F  ( E ) | id

28 id + * ( ) $ E ETE’ E’ E’+TE’ E’ε T TFT’ T’ T’ε T’*FT’ F Fid F(E)

29 Stack Input Action $E id+id*id$ E  T E’ $E’T id+id*id$ T  F T’ $E’T’F id+id*id$ F  id $E’T’id id+id*id$ pop $E’T’ id*id$ T’  ε $E’ id*id$ E’  + T E’ $E’T id*id$ pop $E’T id*id$ T  F T’ $E’T’F id*id$ F  id $E’T’id id*id$ pop $E’T’ *id$ T’  * F T’ Stack Input Action $E’T’F* *id$ pop $E’T’F id$ F  id $E’T’id id$ pop $E’T’ $ T’  ε $E’ $ E’  ε $ $ accept

30 For input: id * id + id can you derive the same parse tree using the table?


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