Subject: Re: why no big-float?
From: Erik Naggum <>
Date: 1996/04/09
Newsgroups: comp.lang.lisp,comp.lang.lisp.mcl
Message-ID: <>

[William D. Gooch]

|   Floats are basicaly for speed, not high precision.

but transcendental functions are usually implemented with floats, even
though most of them can be computed with rationals in series.  this means
that we lose precision in converting from rational to float, and may run
into Dave's original question.  on the other hand, using series to compute
transcendental functions on rationals will require a "cut-off" after a
given precision is reached.  at this point, we might as well implement
"bigflos", and Bruno Haible's CLISP already does that.  unfortunately,
CLISP is byte-compiled and not particularly fast.  it's a tough choice.

(incidentally, several packages exist for C to achieve multiprecision
arithmetic.  they are not very easy to work with.  I think CLISP has done
the right thing when using one such package for Lisp's long float.)

education is for people who can't handle reality the hard way