Understanding C++ Expression Templates - Angelika Langer

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22OO Implementation à la GOFAbstractExprinterpret()TerminalExprinterpret()NonTerminalExprinterpret()Literalconst double vVariabledouble& vBinaryExprAbstractExpr* e1UnaryExprAbstractExpr* einterpret()interpret()AbstractExpr* e2interpret()v...vinterpret()SUMProductinterpret() interpret()... ...e1->interpret() + e2->interpret()e1->interpret() * e2->interpret()© Copyright 1995-2000 by Angelika Langer. All Rights Reserved.http://www.AngelikaLanger.com(43)last update: 11/7/2005 ,21:37The Abstract ExpressionsThe base classes that define the interface common to terminaland nonterminal expressions:class AbstractExpr {public:virtual double eval() const = 0;};class TerminalExpr : public AbstractExpr {};class NonTerminalExpr : public AbstractExpr {};© Copyright 1995-2000 by Angelika Langer. All Rights Reserved.http://www.AngelikaLanger.com(44)last update: 11/7/2005 ,21:37
23The Terminal Expressionsclass Literal : public TerminalExpr {public:Literal(double v) : _val(v) {}double eval() const { return _val; }private:const double _val;};class Variable : public TerminalExpr {public:Variable(double& v) : _val(v) {}double eval() const { return _val; }private:double& _val;};© Copyright 1995-2000 by Angelika Langer. All Rights Reserved.http://www.AngelikaLanger.com(45)last update: 11/7/2005 ,21:37The Non-Terminal Expressionsclass BinaryExpr : public NonTerminalExpr {protected:BinaryExpr(const AbstractExpr* e1, const AbstractExpr* e2): _expr1(e1),_expr2(e2) {}virtual ~BinaryExpr (){ delete const_cast(_expr1);delete const_cast(_expr2);}const AbstractExpr* _expr1;const AbstractExpr* _expr2;};class Sum : public BinaryExpr {public:Sum(const AbstractExpr* e1, const AbstractExpr* e2): BinExpr(e1,e2) {}double eval() const{ return _expr1->eval() + _expr2->eval(); }};© Copyright 1995-2000 by Angelika Langer. All Rights Reserved.http://www.AngelikaLanger.com(46)last update: 11/7/2005 ,21:37
Page 1 and 2: 1Understanding C++Expression Templa
Page 3 and 4: 3Runtime Computation of FactorialTh
Page 5 and 6: 5The RecursionRecursive definition
Page 7 and 8: 7Goal! efficient computation of ari
Page 9 and 10: 9Agenda! compile-time computation o
Page 11 and 12: 11A Typical Composite StructureaCom
Page 13 and 14: 13The ComponentThe base class that
Page 15 and 16: 15A Simplified OO ImplementationEli
Page 17: 17Implementation Using TemplatesDot
Page 20 and 21: 20The Interpreter PatternThe Interp
Page 24 and 25: 24The ClientThe code that creates t
Page 26 and 27: 26The Non-Terminal Expressionstempl
Page 28 and 29: 28First attemptDefine the creator f
Page 30 and 31: 30Fine TuningDefine a helper functi
Page 33 and 34: 33Incorporating FunctionsWe can inc
Page 35 and 36: 35Run-Time PolymorphismClassic obje
Page 37 and 38: 37Run-Time vs. Compile-Time Dispatc
Page 39 and 40: 39The Strategy PatternContextStrate
Page 41 and 42: 41The Strategiesclass Comparator {p
Page 43 and 44: 43The Strategiesclass Ascii {public
Page 45 and 46: 45Examples from Standard C++! sorti
Page 47 and 48: 47Alexandrescu’s Smart Pointer! t
Page 49 and 50: 49Expression Template LibrariesRefe
Page 51: 51Contact InfoAngelika LangerTraini

Understanding C++ Expression Templates - Angelika Langer

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