#2259 ratsubst() doesn't substitute

[Anton Voropaev]

INPUT

build_info();
display2d : false;
e : x*y+y*z;
ratsubst(t,e,e+x^2);
ratsubst(t,e,e+y^2);
ratsubst(t,e,e+z^2);

INPUT AND OUTPUT

(%i1) build_info();
Maxima version: 5.25.0
Maxima build date: 12:0 8/2/2011
Host type: i686-pc-mingw32
Lisp implementation type: Clozure Common Lisp
Lisp implementation version: Version 1.7-r14925M (WindowsX8632)
(%o1)
(%i2) display2d : false;
(%o2) false
(%i3) e : x*y+y*z;
(%o3) y*z+x*y
(%i4) ratsubst(t,e,e+x^2);
(%o4) x^2+t
(%i5) ratsubst(t,e,e+y^2);
(%o5) y^2+t
(%i6) ratsubst(t,e,e+z^2);
(%o6) z^2+y*z+x*y

[Stavros Macrakis]

The original problem is reproducible in 5.47. Here is a similar case I came across:

E: 2*x*y+x$

ratsubst(Q,E,E+x^2); /* x^2+Q */
ratsubst(Q,E,E+z^2); /* z^2+Q */
ratsubst(Q,E,E+x*z^2); /* x*z^2+Q */

but

ratsubst(Q,E,E+x*y^2); /* x*y^2+2*x*y+x */

This is especially frustrating because I'd have thought that ratsubst could use the same workaround that I use by hand:

ratsubst(Q-x,E-x,E+x*y^2); /* x*y^2+Q */

Maxima 5.47.0 SBCL 2.4.9