Subject: Compiler Construction

Question 4(10 Marks! Consider the grammar at the bottom of the page for arithmetic expressions. Write semantic rules to construct a version of the original expression, but that is the reverse of the original string. In the reverse string all the tokens will be in reverse order, but the characters that made up the token will not be reversed (ie, names of identifiers don't change). Use a semantic attribute called rev for this value and rev will be type "string". Here are some examples of E.rev: expression parsed E.rev a + b abc (a+b) (c+d a ba b + a (d+c)(b + a) Notes The subscripts below are only to distinguish different instances of the same non-terminal in a single production Grammar E-ET ET TTF TE Fid FIE