#2533 functions conjugate or diff has bug

None
open
nobody
None
5
2013-01-15
2013-01-15
Valery Lovchikov
No

(%i1) declare(z,complex)$ depends(z,q)$
(%i3) diff(realpart(z),q)-realpart(diff(z,q))
(%o3) 0
(%i4) diff(imagpart(z),q)-imagpart(diff(z,q));
(%o4) 0

but
(%i5) diff(conjugate(z),q)-conjugate(diff(z,q));
is not 0

build_info("5.28.0-2","2012-08-27 23:16:48","i686-pc-mingw32","GNU Common Lisp (GCL)","GCL 2.6.8")

Related

Bugs: #2533

Discussion

  • Well the result, which is

    (%i4) diff(conjugate(z),q)-conjugate(diff(z,q));
                           d                             dz
    (%o4)                  -- (conjugate(z)) - conjugate(--)
                           dq                            dq
    

    is correct. Although the answer is indeed equal to zero mathematically, Maxima doesn't spot that.

    To the developers: Maybe we should simplify diff(conjugate(f(q)), q) to conjugate(diff(f(q), q))? Arguments for: If f is differentiable, so is its conjugate; This creates a canonical form. Arguments against: How does one stop this happening? Yet another flag?

     
  • On Tue, 15 Jan 2013 09:59:25 +0000
    "Rupert Swarbrick" rswarbrick@users.sf.net wrote:

    Well the result, which is

    (%i4) diff(conjugate(z),q)-conjugate(diff(z,q));
    d dz
    (%o4) -- (conjugate(z)) - conjugate(--)
    dq dq

    is correct. Although the answer is indeed equal to zero
    mathematically, Maxima doesn't spot that.

    To the developers: Maybe we should simplify diff(conjugate(f(q)), q) to conjugate(diff(f(q), q))? Arguments for: If f is
    differentiable, so is its conjugate; This creates a canonical form.
    Arguments against: How does one stop this happening? Yet another
    flag?

    Sorry, missed my text.

    We need to act the same way as in the case of realpart and imagpart.
    as

    realpart(diff(z,q))
    is
    'diff(realpart(z),q,1)

    and
    imagpart(diff(z,q))
    is
    'diff(imagpart(z),q,1)

    must also be conjugate(diff(z,q))
    'diff(conjugate(z),q,1)

    But now the result
    conjugate('diff(z,q,1))

    This is the problem.

    Best regards
    Valery Lovchikov


    [bugs:#2533] functions conjugate or diff has bug

    Status: open
    Created: Tue Jan 15, 2013 09:48 AM UTC by Valery Lovchikov
    Last Updated: Tue Jan 15, 2013 09:48 AM UTC
    Owner: nobody

    (%i1) declare(z,complex)$ depends(z,q)$
    (%i3) diff(realpart(z),q)-realpart(diff(z,q))
    (%o3) 0
    (%i4) diff(imagpart(z),q)-imagpart(diff(z,q));
    (%o4) 0

    but
    (%i5) diff(conjugate(z),q)-conjugate(diff(z,q));
    is not 0

    build_info("5.28.0-2","2012-08-27 23:16:48","i686-pc-mingw32","GNU
    Common Lisp (GCL)","GCL 2.6.8")


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    Related

    Bugs: #2533

  • On Tue, 15 Jan 2013 09:59:25 +0000
    "Rupert Swarbrick" rswarbrick@users.sf.net wrote:

    Well the result, which is

    (%i4) diff(conjugate(z),q)-conjugate(diff(z,q));
    d dz
    (%o4) -- (conjugate(z)) - conjugate(--)
    dq dq

    is correct. Although the answer is indeed equal to zero
    mathematically, Maxima doesn't spot that.

    To the developers: Maybe we should simplify diff(conjugate(f(q)), q) to conjugate(diff(f(q), q))? Arguments for: If f is
    differentiable, so is its conjugate; This creates a canonical form.
    Arguments against: How does one stop this happening? Yet another
    flag?

    We need to act the same way as in the case of realpart and imagpart.
    In their case, because there is no problem?

    Valery Lovchikov


    [bugs:#2533] functions conjugate or diff has bug

    Status: open
    Created: Tue Jan 15, 2013 09:48 AM UTC by Valery Lovchikov
    Last Updated: Tue Jan 15, 2013 09:48 AM UTC
    Owner: nobody

    (%i1) declare(z,complex)$ depends(z,q)$
    (%i3) diff(realpart(z),q)-realpart(diff(z,q))
    (%o3) 0
    (%i4) diff(imagpart(z),q)-imagpart(diff(z,q));
    (%o4) 0

    but
    (%i5) diff(conjugate(z),q)-conjugate(diff(z,q));
    is not 0

    build_info("5.28.0-2","2012-08-27 23:16:48","i686-pc-mingw32","GNU
    Common Lisp (GCL)","GCL 2.6.8")


    Sent from sourceforge.net because you indicated interest in
    https://sourceforge.net/p/maxima/bugs/2533/

    To unsubscribe from further messages, please visit
    https://sourceforge.net/auth/prefs/

     

    Related

    Bugs: #2533