[Maxima-bugs] [ maxima-Bugs-574635 ] machine-mantissa-precision hard-wired

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

Bugs item #574635, was opened at 2002-06-27 08:53
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Nobody/Anonymous (nobody)
Assigned to: Nobody/Anonymous (nobody)
Summary: machine-mantissa-precision hard-wired

Initial Comment:
In simp.lisp, the value of machine-mantissa-precision is hard-wired to 24:

(eval-when (compile load)
   (defvar machine-mantissa-precision 24 );;is this correct 
)

This is correct for single-floats.  I'd suggest changing the code
to something like

(eval-when (compile load)
     (defvar machine-mantissa-precision (float-digits 1d0)))


Notes:

1. For some background, see

          http://www.math.utexas.edu/pipermail/maxima/2001/000175.html
          http://www.math.utexas.edu/pipermail/maxima/2001/000177.html
          http://www.math.utexas.edu/pipermail/maxima/2001/000183.html

2.  float.lisp also sets the value of machine-mantissa-precision; it uses

       MACHINE-MANTISSA-PRECISION
        #+(OR PDP10 H6180)   27.
        #+cl(integer-length (integer-decode-float most-positive-double-float))
        ;#+LISPM                     32.
        #+(OR NIL Franz)     56.        ;double-float.  Long would be 113.

Barton Willis

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