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Re: [Bug-apl] 0⍟0

From: Jay Foad
Subject: Re: [Bug-apl] 0⍟0
Date: Wed, 13 Jul 2016 12:29:59 +0100

It's not a tolerant comparison (not that it matters for comparing 0 with 0!). If it was, they would use the standardese "if A is tolerantly-equal-to B". Also section 12.2.1 has an informal note listing functions which use comparison-tolerance, and the list does not include Logarithm.


On 13 July 2016 at 12:21, Juergen Sauermann <address@hidden> wrote:
Hi Jay,

I see. Which leaves the question if "equal" shall be strict or within ⎕IO.

Since we are dealing with real numbers (and therefore often rounding errors) within ⎕IO
makes more sense to me but the standard does not mention ⎕IO for .

/// Jürgen

On 07/13/2016 01:05 PM, Jay Foad wrote:
My ISO ("First edition 2001-02-01") says:

Evaluation Sequence:
  If either of A or B are not numbers signal domain-error.
  If A and B are equal, return one.
  If A is one, signal domain-error.
  Set A1 to the natural-logarithm of A.
  Set B1 to the natural-logarithm of B.
  Return B1 divided-by A1.

0⍟0 falls into the "A and B are equal" case.


On 13 July 2016 at 11:04, Juergen Sauermann <address@hidden> wrote:
Hi Kacper,

my ISO (June 9, 2000) says DOMAIN ERROR.

More precisely, they say that A⍟B is (⍟A)÷
(⍟B) and then that ⍟0 gives DOMAIN ERROR.

/// Jürgen

On 07/12/2016 11:43 PM, Kacper Gutowski wrote:
According to ISO, 0⍟0 should be one.
GNU APL gives:



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