* Add functions sub_matrix() and reduced_matrix().

[ginac.git] / ginac / matrix.cpp

diff --git a/ginac/matrix.cpp b/ginac/matrix.cpp
index 623537febbb965f5ac1324e77f85e07d59a00768..710190376a1c28b59c787d902655aa24d97ccf73 100644 (file)
--- a/ginac/matrix.cpp
+++ b/ginac/matrix.cpp
@@ -1598,4 +1598,52 @@ ex symbolic_matrix(unsigned r, unsigned c, const std::string & base_name, const
        return M;
 }
 
+ex reduced_matrix(const matrix& m, unsigned r, unsigned c)
+{
+       if (r+1>m.rows() || c+1>m.cols() || m.cols()<2 || m.rows()<2)
+               throw std::runtime_error("minor_matrix(): index out of bounds");
+
+       const unsigned rows = m.rows()-1;
+       const unsigned cols = m.cols()-1;
+       matrix &M = *new matrix(rows, cols);
+       M.setflag(status_flags::dynallocated | status_flags::evaluated);
+
+       unsigned ro = 0;
+       unsigned ro2 = 0;
+       while (ro2<rows) {
+               if (ro==r)
+                       ++ro;
+               unsigned co = 0;
+               unsigned co2 = 0;
+               while (co2<cols) {
+                       if (co==c)
+                               ++co;
+                       M(ro2,co2) = m(ro, co);
+                       ++co;
+                       ++co2;
+               }
+               ++ro;
+               ++ro2;
+       }
+
+       return M;
+}
+
+ex sub_matrix(const matrix&m, unsigned r, unsigned nr, unsigned c, unsigned nc)
+{
+       if (r+nr>m.rows() || c+nc>m.cols())
+               throw std::runtime_error("sub_matrix(): index out of bounds");
+
+       matrix &M = *new matrix(nr, nc);
+       M.setflag(status_flags::dynallocated | status_flags::evaluated);
+
+       for (unsigned ro=0; ro<nr; ++ro) {
+               for (unsigned co=0; co<nc; ++co) {
+                       M(ro,co) = m(ro+r,co+c);
+               }
+       }
+
+       return M;
+}
+
 } // namespace GiNaC