[Maxima-bugs] [ maxima-Bugs-1613390 ] find_root evaluates its arguments strangely

[SourceForge.net <no...@so...>]

Bugs item #1613390, was opened at 2006-12-11 10:17
Message generated for change (Tracker Item Submitted) made by Item Submitter
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=104933&aid=1613390&group_id=4933

Please note that this message will contain a full copy of the comment thread,
including the initial issue submission, for this request,
not just the latest update.
Category: Share Libraries
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Nobody/Anonymous (nobody)
Assigned to: Nobody/Anonymous (nobody)
Summary: find_root evaluates its arguments strangely

Initial Comment:
Someone asked a question on the mailing list about using the output of solve to do numerical root finding. 

we found that you could not use the output of solve directly in find_root because it evaluates its first argument strangely. Instead it required explicit evaluation with the '' operator.

This behavior is very confusing even for relatively advanced maxima users, but especially for new users.

example of the problem below:


-----Transcript------

Maxima 5.10.0 http://maxima.sourceforge.net
Using Lisp GNU Common Lisp (GCL) GCL 2.6.7 (aka GCL)


(%i1) h1(s):=1/(1+tau[1]*s);
h2(s):=1/(1+tau[2]*s);
x(s):=1/s;
tau[1]:33e-6;
tau[2]:33e-6;
eqn:first(solve(ilt(h1(s)*h2(s)*x(s),s,t)=0.1,t));
                                           1
(%o1)                         h1(s) := ----------
                                       1 + tau  s
                                              1
(%i2)                                      1
(%o2)                         h2(s) := ----------
                                       1 + tau  s
                                              2
(%i3)                                      1
(%o3)                              x(s) := -
                                           s
(%i4) (%o4)                          3.2999999999999996E-5
(%i5) (%o5)                          3.2999999999999996E-5
(%i6)
`rat' replaced 3.2999999999999996E-5 by 33//1000000 = 3.3000000000000003E-5

`rat' replaced 0.9 by 9//10 = 0.9
                                     1000000 t
                                     ---------
                                        33
                               297 %e          - 330
(%o6)                      t = ---------------------
                                     10000000
(%i7) find_root(%,t,0,2);

Maxima encountered a Lisp error:

 Error in MACSYMA-TOP-LEVEL [or a callee]: ((MEQUAL SIMP) $T
                                            ((MTIMES SIMP)
                                             ((RAT SIMP) 1 10000000)
                                             ((MPLUS SIMP) -330
                                              ((MTIMES SIMP) 297
                                               ((MEXPT SIMP) $%E
                                                ((MTIMES SIMP)
                                                 ((RAT SIMP) 1000000
                                                  33)
                                                 $T)))))) is not of type (OR
                                                                          RATIONAL
                                                                          LISP:FLOAT).



----------------------------------------------------------------------

You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=104933&aid=1613390&group_id=4933