Reference no: EM133703012

1) What is the difference between syntax and semantics?

2) Why is it important for a grammar to be unambiguous?

3) Show that the following grammar is ambiguous - show two distinct parse
trees for one terminal string.
<expr> -> <expr> + <expr> | <expr> * <expr> | ( <expr> ) | a | b| c

4) Show that the following grammar is ambiguous - show two distinct parse
trees for one terminal string.
E-> E + E | id

5) Write in grammar for the language consisting of strings over the alphabet {a,b}
where all strings start with the letter a and can have a's and b's after.

6) Write in grammar for the language over the alphabet {a,b,c} consisting of
strings that start and end with the letter a and have a's b's c's in between.

7) Write in grammar for the language over the alphabet {a,b,c} consisting of
strings where every b is immediately followed by the letter c

8) Write an EBNF statement for a C++ float constant.

9) Compute the weakest precondition for the following assignment statement
given the postcondition.
y = 2y - 1 { y > 1}

10) Compute the weakest precondition for the sequence of statements:

(Statement 1) b = 2b + 1;

(Statement 2) b = b-3{b < 0}

11) Compute the weakest precondition for the selection construct.
if (a == 5)
b = 2b + 1
else
b = 2b;
{b > 1}