Re: division by 0

[Marius Vollmer]

Bernard Urban <address@hidden> writes:

> Debian woody on i386.
>
> $ guile
> guile> (version)
> "1.6.4"
> guile> (/ 0)
> +#.#
> guile> (/ 1.0 0)
> +#.#
> guile> (/ 1 0.0)
> +#.#
> guile>(/ 1 0)
> standard input:3:1: In procedure / in expression (/ 1 0):
> standard input:3:1: Numerical overflow
> ABORT: (numerical-overflow)
>
> Type "(backtrace)" to get more information or "(debug)" to enter the debugger.
> guile>
>
> Problem happens in numbers.c, function scm_divide(), where the test 
> #line 3274 should not be made.

The 1.7 series should be handling this more correctly.  From NEWS:

    ** There is support for Infinity and NaNs.

    Following PLT Scheme, Guile can now work with infinite numbers, and
    'not-a-numbers'.

    There is new syntax for numbers: "+inf.0" (infinity), "-inf.0"
    (negative infinity), "+nan.0" (not-a-number), and "-nan.0" (same as
    "+nan.0").  These numbers are inexact and have no exact counterpart.

    Dividing by an inexact zero returns +inf.0 or -inf.0, depending on the
    sign of the dividend.  The infinities are integers, and they answer #t
    for both 'even?' and 'odd?'. The +nan.0 value is not an integer and is
    not '=' to itself, but '+nan.0' is 'eqv?' to itself.

    For example

        (/ 1 0.0)
        => +inf.0

        (/ 0 0.0)
        => +nan.0

        (/ 0)
        ERROR: Numerical overflow

    Two new predicates 'inf?' and 'nan?' can be used to test for the
    special values.

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