#272 Taylor sometimes prints without ellipses

open
nobody
5
2006-04-09
2003-03-25
No

The ellipsis (+...) is sometimes not displayed on Taylor
series, in particular:

taylor(1,x,0,3)+x^3
taylor(1,x,0,3)*x

even though TaylorInfo shows the truncation information,
it is used for subsequent calculations, and /T/ appears
in the display.

More detail.

Setup---------------------

zero:taylor(0,x,0,3)
one: taylor(1,x,0,3).
onex3: taylor(1+x^3,x,0,3)

Incorrect cases------------------------------------------------

zero+x^3 => x^3
one*x => x
one+x^3 => 1+x^3
(one+x^3)-1 => x^3

Correct cases------------------------------------------------

zero => 0+...
one => 1+...
one+x^4 => 1+...
zero*x => 0+...
one*x-x => 0+...
(one+x^3)-x^3 => 1+...

onex3 => 1+x^3+...
onex3-1 => x^3+...

Discussion

  • Stavros Macrakis

    Logged In: YES
    user_id=588346

    The above is true with psexpand:false (the default).
    Other values of psexpand correct some of the incorrect cases:
    With psexpand:true, they are all displayed correctly.
    With psexpand:multi, one of the four incorrect cases,
    one+x^3, is displayed correctly.

    The core of the problem seems to be in psdisrep(hayat). But
    the logic around TRUNC and PS in form-mrat(nforma) is
    confusing -- what exactly do TRUNC and PS mean separately
    and together?

     
  • Robert Dodier

    Robert Dodier - 2006-04-09
    • labels: --> Lisp Core - Taylor
     

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