Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
1995
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 1995

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Re: Re: Bug in interpretation of mma Series[] command?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg2371] Re: [mg2287] Re: [mg2268] Re: Bug in interpretation of mma Series[] command?
  • From: siegman at ee.stanford.edu (A. E. Siegman)
  • Date: Sun, 29 Oct 1995 22:48:46 -0500
  • Organization: Stanford University

As the original complainant on this topic, I'd just like to reiterate two
quick points in the discussion of why having

      f1[x] * Series[f2[x]]

evaluate to

      Series[f1[x] * f2[x]]

(rather than remain unevaluated, for example, or do something, anything,
else) still seems to me a bad thing.

1)  It's _grossly_ unusual or unfamiliar behavior:

I'd challenge the Wolfram (or other) respondents on this issue to name any
other common situation where

   f1 * Operator[f2]

is _expected_ by a user to behave as  Operator[f1 * f2]  (or maybe 
Operator[f1] * Operator[f2]), with Operator[] being an operator that
really does something to the f's.  The [] symbols are just widely
understood to mark the bounds of what (any)  Operator[]  operates on.

2)  It can lead to, indeed promotes, _large_ undetected errors:

If I understand the situation (and I've missed some of the messages), the
unwanted action is essentially a forced type conversion in combining  f1 
and  Series[f2] .  I think even the relatively unsophisticated user may
understand that if one multiplies or adds an integer and a real there may
be a forced conversion of the product to real, and a small loss of
accuracy.  But this loss in accuracy is normally both small and also of
small import, though it may, of course, be very important in certain rare
cases. 

But a forced (and unnoted) series expansion of  f1  is _likely_ to lead to
_large_ inaccuracies, since the above input is most likely to be used
precisely in situations where  Series[f2] is appropriate and acceptable,
but  Series[f1]  is NOT (which is why f1 was left outside in the first
place).

   --AES


  • Prev by Date: Q on COMBINING PLOTS w/ diff. axes.
  • Next by Date: Re: Numerical Solutions to Schrod Eq with Mathematica
  • Previous by thread: Re: Re: Re: Bug in interpretation of mma Series[] command?
  • Next by thread: simultaneous equations