Question

For a given grammar: X  0 X 0 | 1 X 1 | Y | 1 X 0 | 0 X 1 Y  1 | 0 |  A: Create syntax directed definition (SDD) to get the value and the length of the string. B: SDD should also generate an error message if the given string is not acceptable by the grammar. C: Convert the SDD into an equivalent L-attributed SDD and identify each attribute. D: Convert the L-attributed SDD into an equivalent syntax directed translation (SDT)

Answer 1

Answer:

For a given grammar: X  0 X 0 | 1 X 1 | Y | 1 X 0 | 0 X 1 Y  1 | 0 |  A: Create syntax directed definition (SDD) to get the value and the length of the string. B: SDD should also generate an error message if the given string is not acceptable by the grammar. C: Convert the SDD into an equivalent L-attributed SDD and identify each attribute. D: Convert the L-attributed SDD into an equivalent syntax directed translation (SDT)

Answer 2

Answer:

Given,

X-> 0X0|1X1|Y

Y-> 1|0

A) Create syntax directed definition(SDD)

to get the value and the length of the string

productions       Semantic Rules

X->0X0                     X.Val=0X0                        

X->1X1             X.Val=1X1

X->Y                          Y1=0  

Y->0               Y.Val=0;

Y->1               Y.val=1

Parse Tree

     X-> 0X0|1X1|Y

Y-> 1|0

      X

X

             0

X

0

1

X

1

Y

   

Y

1

or

0

                                           

B) Sdd should also shows error message, if the given string is not accessible by the grammer

bool checkSentence(char str[])

{

   // Calculate the length of the string.

   int len = strlen(str);

 

   // Check that the first character lies in [A-Z].

   // Otherwise return false.

   if (str[0] < 'A' || str[0] > 'Z')

       return false;

}

c) Convert the SDD into an equivalent L-attributed SDD and Identified each attribute

1. S-attributed SDT :

· If an SDT uses only synthesized attributes, it is called as S-attributed SDT.

· S-attributed SDTs are evaluated in bottom-up parsing, as the values of the parent nodes depend upon the values of the child nodes.

· Semantic actions are placed in rightmost place of RHS.

2. L-attributed SDT:

· If an SDT uses both synthesized attributes and inherited attributes with a restriction that inherited attribute can inherit values from left siblings only, it is called as L-attributed SDT.

· Attributes in L-attributed SDTs are evaluated by depth-first and left-to-right parsing manner.

· Semantic actions are placed anywhere in RHS.

Y-> 1|0

X-> 0X0|1X1|Y

D ) Convert the L attribute SDD into an equivalent syntax directed translation (SDT)

X-> 0X0|1X1|Y

Y-> 1|0

X′ → X Accept 1 : x → SL if (S.sign=*)X.val=0 * X.val=0; else X.val =1 X.val=1; 2 : X → + X.sign = ’X’; 3 : X → Y; Y if(Y → 1 or Y.val = 0);

X-> 0X0|1X1|Y

Y-> 1|0

Explanation: