# Rick van der Zwet
# StudentID: 0433373
# $Id: lecture2.txt 248 2007-10-04 19:37:40Z rick $

All quotes are based on the 7th edition of Concepts of programming
languages from Robert W. Sebesta, cause the 8th edition has not come in
yet

*** Chapter 3 Review Questions ***

2)
Q: Who are language descriptions for?
A: "One of the problems ... about a language" pg. 124 sect. 3.1

3)
Q: Describe the operation of a general language generator
A: "A language generator ... it is pushed" pg. 126 sect. 3.2.2

6)
Q: Define a left recursive grammar rule.
A: "In this derivation ... leftmost drivations" pg 130
   Example: <stmt> => <stmt> , <id>
                   |  <id>
            <id> => A | B | C

8)
Q: Distinguish between static and dynamic semantics.
A: "Static semantics is .. at compile time" pg. 142 sec. 3.4.1

9) 
Q: What purpose do predicates service in an attribute grammer?
A: "Predicates functions, which .. with grammar rules." pg. 142. sec.  3.4.2

10)
Q: What is the difference between a synthensized and an inherited
   attribute?
A: "Synthesized attributes are ... across a tree" pg. 143 sect. 3.4.3

13)
Q: What is the problem with using a software pure interpreter for
   operation semantics?
A: "First, the copmlexities ... configured computer." pg. 149

*** Chapter 3 Problem Set ***
19) Compute the weakest precondition for each of the following
    assignment statements and postconditions:

19a)
Q: a = 2 * (b - 1) - 1 {a > 0}
A: 2 * (b - 1) - 1 > 0
A  b > 1.5

19b)
Q: b = (c + 10) / 3 {b > 6}
A: (c + 10) / 3 > 6
   c > 8

19c)
Q: a = a + 2 * b - 1 {a > 1}
A: a + 2 * b - 1 > 1
   b > 0.5a + 1

19d)
Q: x = 2 * y + x - 1 {x > 11}
A: 2 * y + x - 1 > 11
   y > 6 - 0.5x

20) Compute the weakest precondition for each of the following
    assignment statements and postconditions:

20a)
Q: a = 2 * b + 1;
   b = a - 3
   {b < 0}
A: a - 3 < 0
   {a < 3}
   2 * b + 1 < 3
   {b < 1}

20b)
Q: a = 3 * (2 * b + a);
   b = 3 * a - 1
   {b > 5}
A: 3 * a - 1 > 5
   {a > 2}
   6 * 3b + 3a > 2
   18b + 3a > 2
   18b > 2 - 3a