Changeset 1ac173 in git

Timestamp:

Aug 9, 2001, 10:39:10 AM (22 years ago)

Author:

Mathias Schulze <mschulze@…>

Branches:

(u'spielwiese', '91fdef05f09f54b8d58d92a472e9c4a43aa4656f')

Children:

86c1f00ac7423a6cb67b950155c7809798a70e49

Parents:

8444b045c3217f44893e92cc7acc9a1bc7595178

Message:

*mschulze: added commutator


git-svn-id: file:///usr/local/Singular/svn/trunk@5575 2c84dea3-7e68-4137-9b89-c4e89433aadc

File:

• Singular/LIB/linalg.lib (modified) (3 diffs)

Singular/LIB/linalg.lib

@@ -1 +1 @@
 //GMG last modified: 04/25/2000
 //////////////////////////////////////////////////////////////////////////////
-version="$Id: linalg.lib,v 1.16 2001-08-01 13:02:20 mschulze Exp $";
+version="$Id: linalg.lib,v 1.17 2001-08-09 08:39:10 mschulze Exp $";
 category="Linear Algebra";
 info="
@@ -31 +31 @@
  jordanmatrix(e,b); Jordan matrix with eigenvalues e and Jordan block sizes b
  jordanform(M);     Jordan matrix of constant square matrix M
+ commutator(A);     matrix of commutator B->[A,B]=AB-BA 
 ";
 
@@ -1695 +1696 @@
 ///////////////////////////////////////////////////////////////////////////////
 
+proc commutator(matrix A)
+"USAGE:   (A); matrix A
+ASSUME:  A is a square matrix
+RETURN:  matrix C of the commutator B->[A,B]=AB-BA w.r.t. rowwise ordered basis
+EXAMPLE: example commutator; shows examples
+"
+{
+  int n=ncols(A);
+  if(n!=nrows(A))
+  {
+    ERROR("square matrix expected");
+  }
+  int i,j,k;
+  matrix C[n^2][n^2];
+  for(i=0;i<n;i++)
+  {
+    for(j=0;j<n;j++)
+    {
+      for(k=0;k<n;k++)
+      {
+        C[i*n+j+1,k*n+j+1]=C[i*n+j+1,k*n+j+1]+A[i+1,k+1];
+        C[i*n+j+1,i*n+k+1]=C[i*n+j+1,i*n+k+1]-A[k+1,j+1];
+      }
+    }
+  }
+  return(C);
+}
+example
+{ "EXAMPLE:"; echo=2;
+  ring R;
+  matrix A[2][2]=1,2,3,4;
+  print(A);
+  print(commutator(A));
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
 /*
 ///////////////////////////////////////////////////////////////////////////////