| [2] | 1 | # Rick van der Zwet
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| 2 | # StudentID: 0433373
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| 3 | # $Id: lecture2.txt 248 2007-10-04 19:37:40Z rick $
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| 4 |
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| 5 | All quotes are based on the 7th edition of Concepts of programming
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| 6 | languages from Robert W. Sebesta, cause the 8th edition has not come in
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| 7 | yet
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| 8 |
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| 9 | *** Chapter 3 Review Questions ***
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| 10 |
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| 11 | 2)
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| 12 | Q: Who are language descriptions for?
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| 13 | A: "One of the problems ... about a language" pg. 124 sect. 3.1
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| 14 |
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| 15 | 3)
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| 16 | Q: Describe the operation of a general language generator
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| 17 | A: "A language generator ... it is pushed" pg. 126 sect. 3.2.2
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| 18 |
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| 19 | 6)
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| 20 | Q: Define a left recursive grammar rule.
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| 21 | A: "In this derivation ... leftmost drivations" pg 130
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| 22 | Example: <stmt> => <stmt> , <id>
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| 23 | | <id>
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| 24 | <id> => A | B | C
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| 25 |
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| 26 | 8)
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| 27 | Q: Distinguish between static and dynamic semantics.
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| 28 | A: "Static semantics is .. at compile time" pg. 142 sec. 3.4.1
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| 29 |
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| 30 | 9)
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| 31 | Q: What purpose do predicates service in an attribute grammer?
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| 32 | A: "Predicates functions, which .. with grammar rules." pg. 142. sec. 3.4.2
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| 33 |
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| 34 | 10)
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| 35 | Q: What is the difference between a synthensized and an inherited
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| 36 | attribute?
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| 37 | A: "Synthesized attributes are ... across a tree" pg. 143 sect. 3.4.3
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| 38 |
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| 39 | 13)
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| 40 | Q: What is the problem with using a software pure interpreter for
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| 41 | operation semantics?
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| 42 | A: "First, the copmlexities ... configured computer." pg. 149
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| 43 |
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| 44 | *** Chapter 3 Problem Set ***
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| 45 | 19) Compute the weakest precondition for each of the following
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| 46 | assignment statements and postconditions:
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| 47 |
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| 48 | 19a)
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| 49 | Q: a = 2 * (b - 1) - 1 {a > 0}
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| 50 | A: 2 * (b - 1) - 1 > 0
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| 51 | A b > 1.5
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| 52 |
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| 53 | 19b)
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| 54 | Q: b = (c + 10) / 3 {b > 6}
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| 55 | A: (c + 10) / 3 > 6
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| 56 | c > 8
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| 57 |
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| 58 | 19c)
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| 59 | Q: a = a + 2 * b - 1 {a > 1}
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| 60 | A: a + 2 * b - 1 > 1
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| 61 | b > 0.5a + 1
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| 62 |
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| 63 | 19d)
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| 64 | Q: x = 2 * y + x - 1 {x > 11}
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| 65 | A: 2 * y + x - 1 > 11
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| 66 | y > 6 - 0.5x
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| 67 |
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| 68 | 20) Compute the weakest precondition for each of the following
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| 69 | assignment statements and postconditions:
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| 70 |
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| 71 | 20a)
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| 72 | Q: a = 2 * b + 1;
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| 73 | b = a - 3
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| 74 | {b < 0}
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| 75 | A: a - 3 < 0
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| 76 | {a < 3}
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| 77 | 2 * b + 1 < 3
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| 78 | {b < 1}
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| 79 |
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| 80 | 20b)
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| 81 | Q: a = 3 * (2 * b + a);
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| 82 | b = 3 * a - 1
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| 83 | {b > 5}
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| 84 | A: 3 * a - 1 > 5
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| 85 | {a > 2}
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| 86 | 6 * 3b + 3a > 2
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| 87 | 18b + 3a > 2
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| 88 | 18b > 2 - 3a
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