Re: A problem with range objects and floating point numbers

[John W. Eaton]

Does it also bother you that the results of the following two 
expressions are not exactly bit for bit identical?

  linspace (-20, 1, 22) * .1
  linspace (-2, .1, 22)

This is exactly the sort of thing you are comparing, and with binary 
representation of decimal numbers, I don't see a solution that will give 
you the results you seem to want in all cases.  That's just the nature 
of doing binary floating point operations.

I don't think Matlab gives the same results for these expressions 
either, so compatibility isn't an argument for changing Octave's 
behavior here.

I plan to add an option to Octave (enabled by default when using the 
--traditional option) that will cause Octave's range operator to create 
a matrix immediately rather than storing just the base, limit, increment 
(and sometimes number of elements).  That way the two expressions

  (-20:1:1) * .1
  [-20:1:1] * .1

will produce the same values, because the range will be expanded 
immediately into a matrix in both cases.

jwe