diff --git a/bisection.h b/bisection.h
index 331ffce..acb31f6 100644
--- a/bisection.h
+++ b/bisection.h
@@ -2,6 +2,7 @@
 #define _BISECTION_H
 //general bisection search
 //returns dm-1 on failure, otherwise number between dm and hm
+//cmp returns 0 on equal, >0 if first > second argument
 
 template<typename INDEX, typename COMPAR, typename SUBJECT>
 INDEX bisection_find(INDEX dm, INDEX hm, const SUBJECT *key, const SUBJECT *base , unsigned int lead_dimension_base, COMPAR (*cmp)(const SUBJECT *, const SUBJECT *)) 
@@ -23,4 +24,40 @@ while (hm > dm+1);
 return(dm0-1);
 }
 
+
+// interpolation search
+//distance is +-0, on its quality the convergence speed depends
+
+template<typename INDEX, typename DISTANCE, typename SUBJECT>
+int interpolation_find(INDEX dm0, INDEX high, const SUBJECT *x, const SUBJECT *base , unsigned int lead_dimension_base, DISTANCE (*dist)(const SUBJECT *, const SUBJECT *))
+{
+        INDEX low = dm0;
+        INDEX mid;
+	DISTANCE d1,d2,d3,d4;
+
+        while(1)
+		{
+		d1=(*dist)(x,base+low*lead_dimension_base);
+		d2=(*dist)(base+high*lead_dimension_base,x);
+		cout << "intlp "<<low<<" "<<high<<" "<<d1<<" "<<d2<,endl
+		if(d1<=0 || d2 >=0)  break;
+		d3=(*dist)(base+high*lead_dimension_base,base+low*lead_dimension_base);
+	        mid = low + (int)((d1 * (high-low)) / d3+.5); 
+		d4=(*dist)(x,base+mid*lead_dimension_base);
+		cout << "intlp2 "<<mid<<" "<<d3<<" "<<d4<<endl;
+                if(d4>0)
+                    low = mid + 1;
+                else if(d3<0)
+                    high = mid - 1;
+                else
+                    return mid;
+        }  
+
+	if (d1==0) return low;
+	if (d2==0) return high;
+	return dm0-1; // Not found
+}
+
+
+
 #endif