[Maxima-bugs] [ maxima-Bugs-872433 ] rncombine broken

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Bugs item #872433, was opened at 2004-01-07 15:00
Message generated for change (Comment added) made by guno
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Category: Share Libraries
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Barton Willis (willisbl)
Assigned to: Nobody/Anonymous (nobody)
Summary: rncombine broken

Initial Comment:
The function rncombine is broken.

(C1) load("rncomb")$

Lines d2 and d3 are okay, but d4 is bogus

(C2) rncombine(x+y/x);
(D2) y/x+x
(C3) rncombine(x+y/x);
(D3) y/x+x

(C4) rncombine(y+x/y);
(D4) y+x
(C5) build_info();

Maxima version: 5.9.0
Maxima build date: 19:10 2/9/2003
host type: i686-pc-mingw32
lisp-implementation-type: Kyoto Common Lisp
lisp-implementation-version: GCL-2-5.0

Notes:

1.  The function rncombine is supposed to work like
combine, except that it combines terms that have
denominators that differ by a numerical factor.

2. When rncombine is fixed, either the function 
should autoload, or the user documentation should
explain that one must first load rncomb.mac.


Barton

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Comment By: guno (guno)
Date: 2008-06-20 17:14

Message:
Logged In: YES 
user_id=1709853
Originator: NO

hi

maxima/share/simplification/rncomb.mac contains the function rncombine1
from lineno 35 to lineno 50

this function contains the bug
the factor multiplied in line 44 to flist is cancelled out again in line
48 if the "if" branch is taken but it is not cacelled out if the if branch
is not taken. this is the bug.
one can repair this by 
deleting line 44 and by changing line 48 to

then
flist:denomthru(cons(flist*flist_denom,lsplitdum*flist_denom))/flist_denom,

now the function will work correct.
can anybody do this?


   35 rncombine1(list):=block(
   36   [flist,splitdum,lsplitdum,flist_denom],
   37   if list=[] then return(0),
   38   flist:first(list),
   39   if length(list)=1
   40   then return(if inpart(num(flist),0)="+"
   41 	      then rncombine1(args(num(flist)))/denom(flist)
   42 	      else flist),
   43   flist_denom:(flist_denom:denom(flist))/numfactor(flist_denom),
   44   flist:flist*flist_denom,
   45   splitdum:predpartition(rest(list),
   46 			 lambda([dum],numberp(denom(dum)/flist_denom))),
   47   if (lsplitdum:last(splitdum))#[]
   48   then
flist:denomthru(cons(flist,lsplitdum*flist_denom))/flist_denom,
   49   flist+rncombine1(first(splitdum)))$
   50 

guenter

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