Review for Quiz 0

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Question 0-1

Consider the following grammar.

  S ->                 (no tokens)
     | a S b S
     | b S a S

• a. Give a derivation for the sentence b a a b. The tree at right is to prove to you that it is possible.

• b. Give a derivation for the sentence a b a a b b.

• c. Draw a parse tree for the sentence a b a b. (See part (a) for an example of how to indicate a derivation to the empty sentence.)

• d. Give a succinct English description of the language that this grammar describes. This description should not simply describe the grammar, but instead the properties of the sentences in the language.

Solution

Question 0-2

Consider the following C code.

#include <stdio.h>

int p = 5;

void f(int a, int b) {
    a = 2;
    b = 5;
    p = a + p;
}

int main() {
    int a = 3;
    f(a, p);
    printf("%d %d\n", p, a);
    return 0;
}

• a. C++ uses pass-by-value parameters by default. What does this program print?

• b. What would it print if it used pass-by-reference parameters by default instead?

• c. What about pass-by-value-result parameters?

Solution