Re: how to detect division by zero?

[Bernard Urban]

"Rouben Rostamian" <address@hidden> writes:

> Hello Guile users!
> 
> How does one detect the result of a division by 0.0 in guile?
> 
> In guile 1.6.4 we have:
> 
> guile> (/ 1 0.)
> +#.#
> 
> The usual tests are not informative:
> 
> guile> (number? (/ 1 0.))
> #t
> 
> guile> (positive? (/ 1 0.))
> #t
> 

I read recently on this list that
there is some explicit test available for infinity or nan in 1.7. 

I take the opportunity to pinpoint a bug in 1.6.4:
guile
guile> (version)
"1.6.4"
guile> (/ 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> 

In one case, the code in numbers.c for scm_divide computes the hardware
generated positive infinity, in the other an explicit call to
scm_num_overflow is made after testing the divisor value. 

-- 

Bernard Urban