Maybe simp_given() could be modified to throw an exception if the facts are
inconsistent, I'm not sure. I don't think it is broken. I don?t know of
any bugs at all. The behavior with inconsistent assumptions is (maybe)
unpredictable but I am not sure if that is a bug. It looks like the
behavior when the facts are inconsistent is that is uses the facts given up
until it reaches an inconsistency and then just throws that one away and
continues with the next assumption in the list. Maybe the help should just
say that.
kill(all)$
load(pwlimit)$
simp_given(e, [fcts]) ::= buildq([e,fcts], block([_ans],
unwind_protect((_ans:apply(assume, fcts), expand(e,0,0)),
apply(forget,_ans))))$
display2d:false$
facts();
-> []
simp_given(signum(a)+signum(b),a<0,a>0,b<0);
-> -2
facts();
-> []
simp_given(signum(a)+signum(b),a<0,a<=b,b<0);
-> -2
facts();
-> []
simp_given(signum(a)+signum(b),a<0,a<b);
-> signum(b)-1
facts();
-> []
simp_given(signum(a)+2*signum(b)+4*signum(c),a>0,b<c,a>c,a<c);
-> 4*signum(c)+2*signum(b)+1
facts();
-> []
simp_given(signum(a)+2*signum(b)+4*signum(c),a>0,b>a,c>a,a<c);
-> 7
facts();
-> []
simp_given(signum(a)+2*signum(b)+4*signum(c),a>0,b>a,c<a,a>c);
-> 4*signum(c)+3
facts();
-> []
simp_given(signum(a)+2*signum(b)+4*signum(c),a>0,b>a,c>a);
-> 7
simp_given(signum(a)+2*signum(b)+4*signum(c),a>0,b>a,c>b);
-> 7
facts();
-> []
simp_given(signum(a)+2*signum(b)+4*signum(c),a>0,b>a,c>b,c<a);
-> 7
facts();
-> []
RVH
-----Original Message-----
From: Richard Hennessy
Sent: Friday, June 01, 2012 8:20 PM
To: Stavros Macrakis ; Barton Willis
Cc: maxima at math.utexas.edu
Subject: Re: [Maxima] pw.mac
(%i1) simp_given(signum(a),a>0,a<0);
(out1) 1
(%i2) facts();
(out2) [kind(sinh, one_to_one), kind(log, one_to_one), kind(tanh,
one_to_one), kind(log, increasing)]
Yes, if the assumptions are inconsistent who knows what you?re going to get
and Maxima has a weak assume system anyway. If the assumptions are
redundant then I don?t know if it breaks the code. Can you give an example.
Seems okay to me.
Rich
From: Stavros Macrakis
Sent: Friday, June 01, 2012 7:04 PM
To: Richard Hennessy ; Barton Willis
Cc: maxima at math.utexas.edu
Subject: Re: [Maxima] pw.mac
Richard,
I don't know about other issues, but your simp_given won't work right if
some of the assumptions are redundant. You should use the context
mechanism, as Barton now is (see mail below).
I've also encouraged him to rewrite his simp_assuming and with_assumptions
functions using contexts.
-s
---------- Forwarded message ----------
From: Barton Willis <willisb at unk.edu>
Date: Wed, May 16, 2012 at 1:57 PM
Subject: context based version of abs_integrate--no more
simp_assuming
To: "maxima at math.utexas.edu" <maxima at math.utexas.edu>
I committed a new version of abs_integrate that uses contexts instead of the
buggy simp_assuming macro. The new code doesn't have a general purpose
with_assumptions function (or macro) replacement for simp_assuming.
The new version also fixes some other bugs (rtest_abs_integrate bugs 148 and
149).
--bw
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On Fri, Jun 1, 2012 at 6:13 PM, Richard Hennessy <rich.hennessy at verizon.net>
wrote:
"I don't know what your simp_given function looks like, but
(%i27) ctsp(expr,x,c) := limit(expr, x, c, plus) - limit(expr, x, c, minus);
(%o27) ctsp(expr, x, c) := limit(expr, x, c, plus) - limit(expr, x, c,
minus)
(%i28) ctsp(x^2*signum(x-4), x, c);
2 2
(%o28) limit x signum(x - 4) - limit x signum(x - 4)
x -> c+ x -> c-
However, of course:
(%i29) ctsp(u^2*signum(u-4), x, c);
(%o29) 0
Could you have a problem with what the dummy variable is or something?"
I forgot to say kill(all). pw.mac was loaded, it changes the answer for
some reason. If I start with kill(all) then I get what you get. I don't
know why, maybe because of diff and integrate being modified by pw.mac or
abs_integrate.mac. Does limit ever call integrate or diff? Either way this
method does not work.
Rich
PS
simp_given(e, [fcts]) ::= buildq([e,fcts], block([_ans],
unwind_protect((_ans:apply(assume, fcts), expand(e,0,0)),
apply(forget,_ans))));
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