[Chicken-users] IEEE float arithmetic

[John Cowan]

I'd like to have Chicken inexact numbers play nicely as IEEE floats,
since on all practical platforms they *are* IEEE floats.  This involves
the following modifications.

1) Allow the reader to understand Infinity.0, -Infinity.0, and NaN.0 .
These should be defined in the reader as numeric literals.  As a fallback,
they could be defined in Scheme code:

        (define Infinity.0 (* 1.0e307 1.0e307))
        (define -Infinity.0 (* -1.0e307 1.0e307))
        (define NaN.0 (- Infinity.0 -Infinity.0))

This, however, makes them only available in code, not in a Scheme datum.

2) Remove the divide-by-zero trap in inexact division, and allow the IEEE
results to appear openly.  This will mean that (/ 1.0 0.0) will evaluate
to Infinity.0, (/ -1.0 0.0) to -Infinity.0, and (/ 0.0 0.0) to NaN.0.

These literals are already produced by the Scheme printer.  Alternatively,
both reader and printer could be changed to use the SRFI-77 (and draft
R6RS) forms +inf.0, -inf.0, and +nan.0 .

-- 
John Cowan   http://ccil.org/~cowan    address@hidden
We want more school houses and less jails; more books and less arsenals;
more learning and less vice; more constant work and less crime; more
leisure and less greed; more justice and less revenge; in fact, more of
the opportunities to cultivate our better natures.  --Samuel Gompers