[Lemon-commits] [lemon_svn] alpar: r1711 - hugo/trunk/src/work/athos/lp

[Lemon SVN]

Author: alpar
Date: Thu Mar 31 10:34:55 2005
New Revision: 1711

Modified:
   hugo/trunk/src/work/athos/lp/lp_base.h

Log:
LpSolverBase::Expr is documented

Modified: hugo/trunk/src/work/athos/lp/lp_base.h
==============================================================================
--- hugo/trunk/src/work/athos/lp/lp_base.h	(original)
+++ hugo/trunk/src/work/athos/lp/lp_base.h	Thu Mar 31 10:34:55 2005
@@ -34,7 +34,7 @@
   
   ///Internal data structure to convert floating id's to fix one's
     
-  ///\todo This might by implemented to be usable in other places.
+  ///\todo This might be implemented to be also usable in other places.
   class _FixId 
   {
     std::vector<int> index;
@@ -170,8 +170,52 @@
       bool operator!=(Row c) const  {return id==c.id;} 
    };
     
-    ///Linear expression
-    //    typedef SparseLinExpr<Col> Expr;
+    ///Linear expression of variables and a constant component
+    
+    ///This data structure strores a linear expression of the variables
+    ///(\ref Col "Col"s) and also has a constant component.
+    ///
+    ///There are several ways to access and modify the contents of this
+    ///container.
+    ///- Its it fully compatible with \c std::map<Col,double>, so for expamle
+    ///if \c e is an Expr and \c v and \c w are of type \ref Col then you can
+    ///read and modify the coefficients like
+    ///these.
+    ///\code
+    ///e[v]=5;
+    ///e[v]+=12;
+    ///e.erase(v);
+    ///\endcode
+    ///or you can also iterate through its elements.
+    ///\code
+    ///double s=0;
+    ///for(LpSolverBase::Expr::iterator i=e.begin();i!=e.end();++i)
+    ///  s+=i->second;
+    ///\endcode
+    ///(This code computes the sum of all coefficients).
+    ///- Numbers (<tt>double</tt>'s)
+    ///and variables (\ref Col "Col"s) directly convert to an
+    ///\ref Expr and the usual linear operations are defined so  
+    ///\code
+    ///v+w
+    ///2*v-3.12*(v-w/2)+2
+    ///v*2.1+(3*v+(v*12+w+6)*3)/2
+    ///\endcode
+    ///are valid expressions. The usual assignment operations are also defined.
+    ///\code
+    ///e=v+w;
+    ///e+=2*v-3.12*(v-w/2)+2;
+    ///e*=3.4;
+    ///e/=5;
+    ///\endcode
+    ///- The constant member can be set and read by \ref constComp()
+    ///\code
+    ///e.constComp()=12;
+    ///double c=e.constComp();
+    ///\endcode
+    ///
+    ///\note that \ref clear() not only sets all coefficients to 0 but also
+    ///clears the constant components.
     class Expr : public std::map<Col,Value>
     {
     public: