# HG changeset patch
# User jacint
# Date 1131112402 0
# Node ID 3915867b6975357bd7a900a433db75884502c39a
# Parent  896464fe9fbb16785e3cb26beab7bc6b28a66560
throwing an exception if s=t

diff -r 896464fe9fbb -r 3915867b6975 lemon/preflow.h
--- a/lemon/preflow.h	Fri Nov 04 13:20:24 2005 +0000
+++ b/lemon/preflow.h	Fri Nov 04 13:53:22 2005 +0000
@@ -20,6 +20,7 @@
 #include <vector>
 #include <queue>
 
+#include <lemon/error.h>
 #include <lemon/invalid.h>
 #include <lemon/maps.h>
 #include <lemon/graph_utils.h>
@@ -88,10 +89,21 @@
     static const int H0=20;
     static const int H1=1;
 
+  public:
+
+    ///\ref Exception for the case when s=t.
+
+    ///\ref Exception for the case when the source equals the target.
+    class InvalidArgument : public lemon::LogicError {
     public:
-
+      virtual const char* exceptionName() const {
+	return "lemon::Preflow::InvalidArgument";
+      }
+    };
+    
+    
     ///Indicates the property of the starting flow map.
-
+    
     ///Indicates the property of the starting flow map.
     ///The meanings are as follows:
     ///- \c ZERO_FLOW: constant zero flow
@@ -126,8 +138,8 @@
       AFTER_PREFLOW_PHASE_2
     };
     
-    protected: 
-      FlowEnum flow_prop;
+  protected: 
+    FlowEnum flow_prop;
     StatusEnum status; // Do not needle this flag only if necessary.
     
   public: 
@@ -146,8 +158,11 @@
 	      const CapacityMap& _cap, FlowMap& _f) :
 	_g(&_gr), _source(_s), _target(_t), _capacity(&_cap),
 	_flow(&_f), _node_num(countNodes(_gr)), level(_gr), excess(_gr,0), 
-	flow_prop(NO_FLOW), status(AFTER_NOTHING) { }
-
+	flow_prop(NO_FLOW), status(AFTER_NOTHING) { 
+	if ( _source==_target )
+	  throw InvalidArgument();
+      }
+    
 
                                                                               
     ///Runs the preflow algorithm.