From octave-sources-request at bevo dot che dot wisc dot edu  Thu Jan 11 01:56:28 2001
Subject: dot.m ( typo corrected)
From: Rolf Fabian <fabian at tu-cottbus dot de>
To: "'octave-sources UWISC'" <octave-sources at bevo dot che dot wisc dot edu>
Date: Thu, 11 Jan 2001 08:53:01 +0100


Hi,

I've removed some typos in the header section of my previous upload
yesterday. The function body remained unchanged!

Sorry for any inconvenience.

Rolf

--------------------- snip -----------------------


## -*- texinfo -*-
## at deftypefn {Function File} {} dot (@var{x}, @var{y})
##	DOT PRODUCT of two vectors
##
##The dot (inner) product may be legally defined in two flavours:
##(A)	 at var{x}(1)*conj(@var{y}(1)) + .. + @var{x}(N)*conj(@var{y}(N))
##	This definition applies complex conjugation to the  second
##	argument and is preferred in most linear algebra textbooks.
##	It is choosen to be the default method in current function.
##
##(B)	 at conj(var{x}(1))*@var{y}(1) + .. + @conj(var{x}(N))*@var{y}(N)
##	This alternate definition prefers complex conjugation
##	of the first argument and is used as matlab's default.
##
##Both definitions are identical for vectors  at var{x}, @var{y} in 
##euclidian (real) space,  but differ in unitary (complex) space. 
##Switching between both definitions may be controlled by setting
##variable 'global dot_arg_conj_prefer' =2 (A)  or =1 (B).
##
##Simple properties
##dot( at var(x),C*@var(y)) == conj( C ) * dot(@var(x),@var(y))  (A)
##                       ==       C   * dot( at var(x),@var(y))  (B)
##dot(C* at var(x),@var(y)) ==       C   * dot(@var(x),@var(y))  (A)
##                       == conj( C ) * dot( at var(x),@var(y))  (B)
##dot(  ) ==        norm(  at var(x) )^2        (A ) ==        norm( @var(x) )^2        (A|B)
##dot(  ) == conj( dot(  at var(y),@var(x) ) )  (A ) == conj( dot( @var(y),@var(x) ) )  (A|B)
##
##The input vectors may pocess any combination of row/column
##orientation, but their length N must be the same.
## at end deftypefn

##AUTHOR Rolf Fabian <fabian at tu-cottbus dot de>   Jan. 11, 2001
##	 published under current GNU GENERAL PUBLIC LICENSE

function z = dot(x,y)

if	(nargin != 2)
	usage ("dot( x,y )");
endif

if      exist("dot_arg_conj_prefer")==1
        global dot_arg_conj_prefer;
        DACP=dot_arg_conj_prefer;
	if	all([1,2]!=DACP), error(\
        "dot: invalid global \'dot_arg_conj_prefer\' .. set to 1|2");
	endif
else	DACP=2;
endif

save_do_fortran_indexing = do_fortran_indexing;

unwind_protect
	do_fortran_indexing = 1;

	if	( any(size(x)==1) && any(size(y)==1) && length(x)==length(y) )
		if	DACP==2
			z = x(:).' * conj( y(:) );	#conj 2nd arg
		elseif	DACP==1
			z = x(:)'  * y(:);		#conj 1st arg
		endif
	else
		error ("dot: both arguments must be vectors of the same length");
	endif

unwind_protect_cleanup

	do_fortran_indexing = save_do_fortran_indexing;

end_unwind_protect

endfunction



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