Fix calculator-string-to-number yet again (bug#47694)

* lisp/calculator.el (calculator-string-to-number):
The last bugfix changed the code to just blindly replace ".e".  This
has some minor problems like making "-." parse as 0.0 instead of -0.0,
and ".1.e1" is parsed as 1 instead of 0.1.  Instead, replace the first
"." that is followed by a non-digit with ".0".  Since this has had
several problems over the years, add some tests too.  (Also, restore
the original if-indentation style.)

2 files changed, 56 insertions, 4 deletions

diff --git a/lisp/calculator.el b/lisp/calculator.el
index 6dd8d9a7ec1..99c9b6290c4 100644
--- a/lisp/calculator.el
+++ b/lisp/calculator.el
@@ -836,10 +836,11 @@ The result should not exceed the screen width."
   "Convert the given STR to a number, according to the value of
 `calculator-input-radix'."
   (if calculator-input-radix
-      (string-to-number str (cadr (assq calculator-input-radix
-                                        '((bin 2) (oct 8) (hex 16)))))
-    ;; Allow entry of "1.e3".
-    (let ((str (replace-regexp-in-string (rx "." (any "eE")) "e" str)))
+    (string-to-number str (cadr (assq calculator-input-radix
+                                      '((bin 2) (oct 8) (hex 16)))))
+    ;; parse numbers similarly to calculators
+    ;; (see tests in test/lisp/calculator-tests.el)
+    (let ((str (replace-regexp-in-string "\\.\\([^0-9].*\\)?$" ".0\\1" str)))
       (float (string-to-number str)))))
 
 (defun calculator-push-curnum ()
diff --git a/test/lisp/calculator-tests.el b/test/lisp/calculator-tests.el
new file mode 100644
index 00000000000..9551b1a4c61
--- /dev/null
+++ b/test/lisp/calculator-tests.el
@@ -0,0 +1,51 @@
+;;; calculator-tests.el --- Test suite for calculator. -*- lexical-binding: t -*-
+
+;; Copyright (C) 2021 Free Software Foundation, Inc.
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Code:
+(require 'ert)
+(require 'calculator)
+
+(ert-deftest calculator-test-calculator-string-to-number ()
+  (dolist (x '((""          0.0)
+               ("+"         0.0)
+               ("-"         0.0)
+               ("."         0.0)
+               ("+."        0.0)
+               ("-."       -0.0)
+               (".-"        0.0)
+               ("--."       0.0)
+               ("-0.0e"    -0.0)
+               ("1e1"      10.0)
+               ("1e+1"     10.0)
+               ("1e-1"      0.1)
+               ("+1e1"     10.0)
+               ("-1e1"    -10.0)
+               ("+1e-1"     0.1)
+               ("-1e-1"    -0.1)
+               (".1.e1"     0.1)
+               (".1..e1"    0.1)
+               ("1e+1.1"   10.0)
+               ("-2e-1.1"  -0.2)))
+    (pcase x
+      (`(,str ,expected)
+       (let ((calculator-input-radix nil))
+         (should (equal (calculator-string-to-number str) expected)))))))
+
+(provide 'calculator-tests)
+;; calculator-tests.el ends here