GNU bug report logs - #41347
28.0.50; calculator.el: Cannot input negative exponents

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Mattias Engdegård <mattiase <at> acm.org>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#41347: closed (28.0.50; calculator.el: Cannot input negative
 exponents)
Date: Mon, 18 May 2020 09:29:02 +0000

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Your message dated Mon, 18 May 2020 11:28:21 +0200
with message-id <4D0C7ECD-7179-435A-9783-08F05E8CC204 <at> acm.org>
and subject line Re: bug#41347: 28.0.50; calculator.el: Cannot input negative exponents 
has caused the debbugs.gnu.org bug report #41347,
regarding 28.0.50; calculator.el: Cannot input negative exponents
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


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From: Chris Zheng <chriszheng99 <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 28.0.50; calculator.el: Cannot input negative exponents
Date: Sun, 17 May 2020 13:53:12 +0800

Hello,

With current master, starting Emacs with `-Q`:

1. M-x calculator
2. Input 1e-3 RET

You will get 1 instead of 0.001. I believe this happens since Emacs 26.1. The root cause is the `calculator-string-to-number` function in lisp/calculator.el. Now the function gives

(calculator-string-to-number "1e-3") => 1.0
(calculator-string-to-number "1e3") => 1000.0
(calculator-string-to-number "1e") => 1.0

The funcional code is 

(replace-regexp-in-string
                 "[eE][+-]?\\([^0-9].*\\)?$" "e0\\1" str)

It changes `1e-3` to `1e0-3` that is recognized as 1. I have a possible fix attached below. Please see if it is correct. 

Thank you,

Chris Zheng



From 7693d7072e4787c4b0663f490be5d83c1d9a6ee3 Mon Sep 17 00:00:00 2001
From: Chris Zheng <chriszheng99 <at> gmail.com>
Date: Sun, 17 May 2020 13:43:35 +0800
Subject: [PATCH 1/1] Fix calculator exponent input

* lisp/calculator.el (calculator-string-to-number): Change the regexp
to correctly deal with negative exponents.
---
 lisp/calculator.el | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lisp/calculator.el b/lisp/calculator.el
index 7e0b2fcc6a..fa3eb19099 100644
--- a/lisp/calculator.el
+++ b/lisp/calculator.el
@@ -863,7 +863,7 @@ calculator-string-to-number
     (let* ((str (replace-regexp-in-string
                  "\\.\\([^0-9].*\\)?$" ".0\\1" str))
            (str (replace-regexp-in-string
-                 "[eE][+-]?\\([^0-9].*\\)?$" "e0\\1" str)))
+                 "[eE]\\([+-]?\\)?$" "e\\10" str)))
       (float (string-to-number str)))))
 
 (defun calculator-push-curnum ()
-- 
2.16.1.windows.1

[Message part 3 (message/rfc822, inline)]

From: Mattias Engdegård <mattiase <at> acm.org>
To: Eli Barzilay <eli <at> barzilay.org>
Cc: 41347-done <at> debbugs.gnu.org, Chris Zheng <chriszheng99 <at> gmail.com>
Subject: Re: bug#41347: 28.0.50; calculator.el: Cannot input negative
 exponents 
Date: Mon, 18 May 2020 11:28:21 +0200

[Message part 4 (text/plain, inline)]

17 maj 2020 kl. 22.26 skrev Eli Barzilay <eli <at> barzilay.org>:

> the idea is to mimic common calculators
> where you can type "3." or "3e" and get 3.

Thank you Eli! I can confirm that after removing all the string transformation prior to the call to string-to-number, everything works as expected except "1.e3" (dot before E). A single transformation taking care of that case was added for the sake of completeness.

The attached patch has now been pushed to master.

[0001-Fix-calculator-entry-of-numbers-with-negative-expone.patch (application/octet-stream, attachment)]

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