New function psi to compute the digamma function. * libinterp/corefcn/psi.cc: file for the new function file (implementation is actually in lo-specfun.cc). * liboctave/numeric/lo-specfun.cc, liboctave/numeric/lo-specfun.h: added implementation of the digamma (psi )function. Partly based on diGamma() from XLiFE++ 1.1 (file gammaFunctions.cpp which was previously melina++) which is under GPL 3 or later and why D. Martin is also added to copyright. * doc/interpreter/arith.txi: add function entry to the manual. * libinterp/corefcn/module.mk: add file to the build system. * NEWS: note new function.

--- a/doc/interpreter/arith.txi	Fri May 01 13:14:23 2015 -0700
+++ b/doc/interpreter/arith.txi	Sun Mar 15 03:31:16 2015 +0000
@@ -315,6 +315,8 @@
 @anchor{XREFgammaln}
 @DOCSTRING(lgamma)
 
+@DOCSTRING(psi)
+
 @node Rational Approximations
 @section Rational Approximations