LOGIC AND DISCRETE MATHEMATICS

Transcription

1 LOGIC AND DISCRETE MATHEMATICS A Computer Science Perspective WINFRIED KARL GRASSMANN Department of Computer Science University of Saskatchewan JEAN-PAUL TREMBLAY Department of Computer Science University of Saskatchewan PRENTICE HALL, Upper Saddle River, New Jersey 07458

2 Preface xv Propositional Calculus Logical Arguments and Propositions Introduction Some Important Logical Arguments Propositions 4 Logical Connectives Introduction Negation Conjunction Disjunction Conditional Biconditional Further Remarks on Connectives 12 Compound Propositions Introduction Logical Expressions Analysis of Compound Propositions Precedence Rules Evaluation of Expressions and Truth Tables Examples of Compound Propositions 21 Tautologies and Contradictions Introduction 23 Tautologies 24 19

3 yi Contents Tautologies and Sound Reasoning Contradictions Important Types of Tautologies Logical Equivalences and Their Use Introduction Proving Logical Equivalences by Truth Tables Statement Algebra Removing Conditionals and Biconditionals Essential Laws for Statement Algebra Shortcuts for Manipulating Expressions Normal Forms Truth Tables and Disjunctive Normal Forms Conjunctive Normal Forms and Complementation Logical Implications and Derivations Introduction Logical Implications Soundness Proofs through Truth Tables Proofs Systems for Derivations The Deduction Theorem 52 Predicate Calculus Syntactic Components of Predicate Calculus Introduction 60.2 The Universe of Discourse 60.3 Predicates 61.4 Variables and Instantiations 63.5 Quantifiers 65.6 Restrictions of Quantifiers to Certain Groups Interpretations and Validity Introduction Interpretations Validity Invalid Expressions Proving Validity Derivations Introduction Universal Instantiation Universal Generalization Deduction Theorem and Universal Generalization Dropping the Universal Quantifiers Existential Generalization Existential Instantiation 88

4 vii 2.4 Logical Equivalences Introduction Basic Logical Equivalences Other Important Equivalences Equational Logic Introduction Equality Equality and Uniqueness Functions and Equational Logic Function Compositions Properties of Operators Identity and Zero Elements Derivations in Equational Logic Equational Logic in Practice Boolean Algebra 115 Induction and Recursion Induction on Natural Numbers Introduction Natural Numbers Mathematical Induction Induction for Proving Properties of Addition Changing the Induction Base Strong Induction Sums and Related Constructs Introduction Recursive Definitions of Sums and Products Identities Involving Sums Double Sums and Matrices Proof by Recursion Introduction Recursive Definitions Descending Sequences The Principle of Proofs by Recursion Structural Induction Applications of Recursion to Programming Introduction Programming as Function Composition Recursion in Programs Programs Involving Trees Recursive Functions Introduction Primitive Recursive Functions 168

5 viii Contents Programming and Primitive Recursion Minimalization 173 Prolog Basic Prolog 178 Introduction 178 Facts, Rules, and Queries 179 Derivations Involving Facts 181 Derivations Involving Rules 183 Instantiations and Unification 186 Backtracking 188 Resolution 190 Running and Testing Programs Introduction Prolog Compilers and Interpreters Consulting a Database Debugging and Tracing 196 Additional Features of Prolog Introduction Input and Output Structures Infix Notation Arithmetic Equality Predicates 201 Recursion Introduction Recursive Predicates Termination Loops and Prolog Lists Recursive Predicates Involving Lists Successive Refinement 213 Negation in Prolog Introduction Prolog as a Logic Language Negation as Failure Use of the Clause Order Cuts 220 Application of Prolog to Logic Introduction 222 Lists as Logical Expressions 222 Representing Logical Expressions as Structures 224

6 ix Sets and Relations Sets and Set Operations Introduction 230 Sets and Their Members 231 Subsets 233 Intersections 235 Unions 236 Differences and Complements 237 Expressions Involving Sets 239 Tuples, Sequences, and Powersets Introduction Tuples and Cartesian Products Sequences and Strings Powersets Types and Signatures 248 Relations Introduction 251 Relations and Their Representation Domains and Ranges 254 Some Operations on Relations 255 Composition of Relations 257 Examples 261 Properties of Relations Introduction Relations on a Set Reflective Relations Symmetric Relations Transitivity Closures Equivalence Relations Partial Orders More About Functions Representations and Manipulations Involving Functions Introduction Definitions and Notation Representations of Functions The Lambda Notation Restrictions and Overloading Composition of Functions Injections, Surjections, and Inverses Creating Inverses by Creating Types 296

7 6.2 Enumerations, Isomorphisms, and Homomorphisms Introduction Enumerations Countable and Uncountable Sets Permutations and Combinations Isomorphisms and Homomorphisms Computational Complexity Introduction Polynomials and Polynomial-time Algorithms Functions and Algorithms Related to Exponentials The Limits of Computability Asymptotic Analysis Divide and Conquer Nondeterministic Polynomial Recurrence Relations Introduction Homogeneous Recurrence Relations Nonhomogeneous Recurrence Relations Miranda Introduction Command Level Function Definitions Types, Functions, and Declarations Pattern Matching and Rewriting A Programming Problem 348 Graphs and Trees Introduction and Examples of Graph Modeling Basic Definitions of Graph Theory 362 _7.3 Paths, Reachability, and Connectedness Computing Paths from a Matrix Representation of Graphs Traversing Graphs Represented as Adjacency Lists Introduction Adjacency Lists Representation of Graphs Breadth-first Search Depth-first Search Dijkstra's Algorithm for Finding Minimum Paths Trees and Spanning Trees Introduction Free Trees Spanning Trees Minimum Spanning Trees 416

8 xi 7.7 Scheduling Networks Introduction A Project Management Model Topological Sorting Formal Requirement Specification in Z Introduction Software Life Cycle Need for Formal Specifications Introduction to Z Introduction Alphabet and Lexical Elements Types and Declarations Specifying a System with Logic and Sets Schemas Relations Functions Sequences 472 Program Correctness Proofs Preliminary Concepts Introduction Programs and Codes Assertions Correctness General Rules Involving Preconditions and Postconditions Introduction Precondition Strengthening Postcondition Weakening Conjunction and Disjunction Rules Correctness Proofs in Loopless Code Introduction Assignment Statements Concatenation of Code The If-Statement Loops and Arrays Introduction A Preliminary While Rule The General While Rule Arrays Program Termination 515

9 xii Contents 10 Grammars, Languages, and Parsing Languages and Grammars Introduction Discussion of Grammars Formal Definition of a Language Notions of Syntax Analysis Ambiguous Grammars Reduced Grammars Top-down Parsing Introduction General Top-down Parsing Strategy Deterministic Top-down Parsing with LL(1) Grammars Derivations Derivations in Propositional Calculus Introduction Basics of Natural Derivation Implementation of the Deduction Theorem Resolution Some Results from Predicate Calculus Introduction Complements Prenex Normal Forms Derivations in Predicate Calculus Introduction Canonical Derivations Quantifiers in Natural Deduction Replacing Quantifiers by Functions and Free Variables Resolution in Predicate Calculus An Overview of Relational Database Systems Basic Concepts Introduction Definitions and Concepts Introductory Example of a Relational Database Overview of a Database System Relational Data Model Introduction 600 c Overview of the Relational Structure Relations and Their Schemas 602

10 xiii Representing Relations in the Relational Model Integrity Rules Relational Algebra Introduction Basic Operations Additional Relational Operations Examples Relational Calculus Introduction Tuple Calculus Examples Structured Query Language Introduction Data Definition Data Management Data Queries Concluding Remarks 637 Bibliography 641 Solutions to Even-numbered Problems 644 Index 736