[Maxima-discuss] letsimp uses ?varlist and ?genvar

[Litvinov S. <sli...@gm...>]

For some functions in src/rat3e.lisp the state of global variable
?genvar is modified and is used on the next call:

(%i1) ?print(rat(a))$

((MRAT SIMP ($A) (#:A16349)) (#:A16349 1 1) . 1) 
(%i2) ?print(?genvar)$

(#:A16349) 
(%i3) ?print(rat(42))$

((MRAT SIMP NIL (#:A16349)) 42 . 1)

I think it is so by design and is probably OK. But `letsimp' assumes
that ?genvar and ?varlist are in consistent state. Note that ?varlist
is modified by `meval*` (src/suprv1.lisp).

The following example is OK because meval* is not called between
`ratexpand' and `letsimp'

(%i1) let(U,T);
(%o1)                               U --> T
(%i2) (ratexpand(a*b*c), print(?genvar), print(?varlist), letsimp(U/n));
(a16349, b16350, c16351) 
(a, b, c) 
                                       T
(%o2)                                  -
                                       n

This gives a wrong result

(%i1) let(U,T)$
(%i2) ratexpand(a*b*c)$
(%i3) ?print(?genvar)$

(#:A16349 #:B16350 #:C16351) 
(%i4) ?print(?varlist)$

NIL 
(%i5) letsimp(U/n);
(%o5)                                  1


(%i5) build_info();
(%o5) 
Maxima version: "branch_5_33_base_1_g4fcaa85"
Maxima build date: "2014-04-04 00:58:37"
Host type: "x86_64-unknown-linux-gnu"
Lisp implementation type: "CLISP"
Lisp implementation version: "2.49 (2010-07-07) (built 3577466571)
(memory 3605554722)"