Channels ▼
RSS

C++ Expression Templates


March 2003/C++ Expression Templates

Listing 1: Source code for object-oriented technique

class AbstractExpr {
public:
   virtual double eval() const = 0;
};

class TerminalExpr : public AbstractExpr {
};

class NonTerminalExpr : public AbstractExpr {
};

class 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;
};

class BinaryExpr : public NonTerminalExpr {
protected:
   BinaryExpr(const AbstractExpr* e1, const AbstractExpr* e2) 
     : _expr1(e1),_expr2(e2) {}
   virtual ~BinaryExpr () 
   { delete const_cast<AbstractExpr*>(_expr1); 
     delete const_cast<AbstractExpr*>(_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(); }
};

...
— End of Listing —


Related Reading


More Insights






Currently we allow the following HTML tags in comments:

Single tags

These tags can be used alone and don't need an ending tag.

<br> Defines a single line break

<hr> Defines a horizontal line

Matching tags

These require an ending tag - e.g. <i>italic text</i>

<a> Defines an anchor

<b> Defines bold text

<big> Defines big text

<blockquote> Defines a long quotation

<caption> Defines a table caption

<cite> Defines a citation

<code> Defines computer code text

<em> Defines emphasized text

<fieldset> Defines a border around elements in a form

<h1> This is heading 1

<h2> This is heading 2

<h3> This is heading 3

<h4> This is heading 4

<h5> This is heading 5

<h6> This is heading 6

<i> Defines italic text

<p> Defines a paragraph

<pre> Defines preformatted text

<q> Defines a short quotation

<samp> Defines sample computer code text

<small> Defines small text

<span> Defines a section in a document

<s> Defines strikethrough text

<strike> Defines strikethrough text

<strong> Defines strong text

<sub> Defines subscripted text

<sup> Defines superscripted text

<u> Defines underlined text

Dr. Dobb's encourages readers to engage in spirited, healthy debate, including taking us to task. However, Dr. Dobb's moderates all comments posted to our site, and reserves the right to modify or remove any content that it determines to be derogatory, offensive, inflammatory, vulgar, irrelevant/off-topic, racist or obvious marketing or spam. Dr. Dobb's further reserves the right to disable the profile of any commenter participating in said activities.

 
Disqus Tips To upload an avatar photo, first complete your Disqus profile. | View the list of supported HTML tags you can use to style comments. | Please read our commenting policy.
 

Video