X-Git-Url: http://git.tdb.fi/?a=blobdiff_plain;f=source%2Flinal%2Fsquarematrix.h;h=5117bb3fa189ee4339d0ce52cdbb4d2ff141b83b;hb=e4b75401bd773201deb00eff672ee34794479671;hp=ee86e13921219702fa58a682c4b5ab2bb5cfb290;hpb=e0d926c9c177ec28f1aaf326a6921438de9db9a3;p=libs%2Fmath.git

diff --git a/source/linal/squarematrix.h b/source/linal/squarematrix.h
index ee86e13..5117bb3 100644
--- a/source/linal/squarematrix.h
+++ b/source/linal/squarematrix.h
@@ -1,6 +1,7 @@
 #ifndef MSP_LINAL_SQUAREMATRIX_H_
 #define MSP_LINAL_SQUAREMATRIX_H_
 
+#include <cmath>
 #include <stdexcept>
 #include "matrix.h"
 
@@ -14,6 +15,10 @@ public:
 	virtual ~not_invertible() throw() { }
 };
 
+/**
+A mathematical matrix with S rows and columns.  Some operations are provided
+here that are only possible for square matrices.
+*/
 template<typename T, unsigned S>
 class SquareMatrix: public Matrix<T, S, S>
 {
@@ -48,19 +53,21 @@ SquareMatrix<T, S> &SquareMatrix<T, S>::operator*=(const SquareMatrix<T, S> &m)
 template<typename T, unsigned S>
 SquareMatrix<T, S> &SquareMatrix<T, S>::invert()
 {
+	using std::abs;
+
 	SquareMatrix<T, S> r = identity();
 	for(unsigned i=0; i<S; ++i)
 	{
-		if(this->element(i, i)==T(0))
-		{
-			unsigned pivot = i;
-			for(unsigned j=i+1; j<S; ++j)
-				if(abs(this->element(j, i))>abs(this->element(pivot, i)))
-					pivot = j;
+		unsigned pivot = i;
+		for(unsigned j=i+1; j<S; ++j)
+			if(abs(this->element(j, i))>abs(this->element(pivot, i)))
+				pivot = j;
 
-			if(pivot==i)
-				throw not_invertible();
+		if(this->element(pivot, i)==T(0))
+			throw not_invertible();
 
+		if(pivot!=i)
+		{
 			this->exchange_rows(i, pivot);
 			r.exchange_rows(i, pivot);
 		}