added mutable keywords to polynomial root property.

Author: meiyasan

math/mathmore/inc/Math/Polynomial.h

@@ -116,20 +116,20 @@ class Polynomial : public ParamFunction<IParamGradFunction>,
       equation is very small. In that case it might be more robust to use the numerical method, by calling directly FindNumRoots()
 
    */
-   const std::vector<std::complex <double> > & FindRoots();
+   const std::vector<std::complex <double> > & FindRoots() const;
 
    /**
       Find the only the real polynomial roots.
       For n <= 4, the roots are found analytically while for larger order an iterative numerical method is used
       The numerical method used is from GSL (see <A HREF="https://www.gnu.org/software/gsl/doc/html/poly.html">documentation</A> )
    */
-   std::vector<double > FindRealRoots();
+   std::vector<double > FindRealRoots() const;
 
    /**
       Find the polynomial roots using always an iterative numerical methods
       The numerical method used is from GSL (see <A HREF="https://www.gnu.org/software/gsl/doc/html/poly.html">documentation</A> )
    */
-   const std::vector<std::complex <double> > & FindNumRoots();
+   const std::vector<std::complex <double> > & FindNumRoots() const;
 
    /**
       Order of Polynomial
@@ -166,8 +166,7 @@ class Polynomial : public ParamFunction<IParamGradFunction>,
    mutable std::vector<double> fDerived_params;
 
    // roots
-
-   std::vector< std::complex < double > > fRoots;
+   mutable std::vector< std::complex < double > > fRoots;
 
 };
 

math/mathmore/src/Polynomial.cxx

@@ -148,7 +148,7 @@ IGenFunction * Polynomial::Clone() const {
 }
 
 
-const std::vector< std::complex <double> > &  Polynomial::FindRoots(){
+const std::vector< std::complex <double> > &  Polynomial::FindRoots() const {
 
 
     // check if order is correct
@@ -234,7 +234,7 @@ const std::vector< std::complex <double> > &  Polynomial::FindRoots(){
   }
 
 
-std::vector< double >  Polynomial::FindRealRoots(){
+std::vector< double >  Polynomial::FindRealRoots() const {
   FindRoots();
   std::vector<double> roots;
   roots.reserve(fOrder);
@@ -244,7 +244,7 @@ std::vector< double >  Polynomial::FindRealRoots(){
   }
   return roots;
 }
-const std::vector< std::complex <double> > &  Polynomial::FindNumRoots(){
+const std::vector< std::complex <double> > &  Polynomial::FindNumRoots() const {
 
 
     // check if order is correct