X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=blobdiff_plain;f=doc%2Ftutorial%2Fginac.texi;h=06ab56fe55ae1c9baed9498d7d2bbcf48d35de33;hp=9c28e7e7b0c6adc5cef8d8b762c43fd3b819b6ac;hb=4102c379eb11a8b9e10adfe4229995e9823c6851;hpb=81c621e4ff1f3e0fdce06b71908f88172666bafa

diff --git a/doc/tutorial/ginac.texi b/doc/tutorial/ginac.texi
index 9c28e7e7..06ab56fe 100644
--- a/doc/tutorial/ginac.texi
+++ b/doc/tutorial/ginac.texi
@@ -481,12 +481,10 @@ so if you have a different compiler you are on your own.  For the
 configuration to succeed you need a Posix compliant shell installed in
 @file{/bin/sh}, GNU @command{bash} is fine.  Perl is needed by the built
 process as well, since some of the source files are automatically
-generated by Perl scripts.  Last but not least, Bruno Haible's library
-CLN is extensively used and needs to be installed on your system.
-Please get it either from @uref{ftp://ftp.santafe.edu/pub/gnu/}, from
-@uref{ftp://ftpthep.physik.uni-mainz.de/pub/gnu/, GiNaC's FTP site} or
-from @uref{ftp://ftp.ilog.fr/pub/Users/haible/gnu/, Bruno Haible's FTP
-site} (it is covered by GPL) and install it prior to trying to install
+generated by Perl scripts.  Last but not least, the CLN library
+is used extensively and needs to be installed on your system.
+Please get it from @uref{ftp://ftpthep.physik.uni-mainz.de/pub/gnu/}
+(it is covered by GPL) and install it prior to trying to install
 GiNaC.  The configure script checks if it can find it and if it cannot
 it will refuse to continue.
 
@@ -1974,6 +1972,38 @@ by @samp{c}) unit matrix. And finally, @code{symbolic_matrix} constructs a
 matrix filled with newly generated symbols made of the specified base name
 and the position of each element in the matrix.
 
+Matrices often arise by omitting elements of another matrix. For
+instance, the submatrix @code{S} of a matrix @code{M} takes a
+rectangular block from @code{M}. The reduced matrix @code{R} is defined
+by removing one row and one column from a matrix @code{M}. (The
+determinant of a reduced matrix is called a @emph{Minor} of @code{M} and
+can be used for computing the inverse using Cramer's rule.)
+
+@cindex @code{sub_matrix()}
+@cindex @code{reduced_matrix()}
+@example
+ex sub_matrix(const matrix&m, unsigned r, unsigned nr, unsigned c, unsigned nc);
+ex reduced_matrix(const matrix& m, unsigned r, unsigned c);
+@end example
+
+The function @code{sub_matrix()} takes a row offset @code{r} and a
+column offset @code{c} and takes a block of @code{nr} rows and @code{nc}
+columns. The function @code{reduced_matrix()} has two integer arguments
+that specify which row and column to remove:
+
+@example
+@{
+    matrix m(3,3);
+    m = 11, 12, 13,
+        21, 22, 23,
+        31, 32, 33;
+    cout << reduced_matrix(m, 1, 1) << endl;
+    // -> [[11,13],[31,33]]
+    cout << sub_matrix(m, 1, 2, 1, 2) << endl;
+    // -> [[22,23],[32,33]]
+@}
+@end example
+
 Matrix elements can be accessed and set using the parenthesis (function call)
 operator:
 
@@ -3778,7 +3808,6 @@ avoided.
 * Built-in Functions::              List of predefined mathematical functions.
 * Multiple polylogarithms::
 * Complex Conjugation::
-* Built-in Functions::              List of predefined mathematical functions.
 * Solving Linear Systems of Equations::
 * Input/Output::                    Input and output of expressions.
 @end menu