Backport: Handle the `neg' operator in some calc-units functions.

* lisp/calc/calc-units.el (math-units-in-expr-p)
(math-single-units-in-expr-p, math-find-compatible-unit-rec)
(math-extract-units): Handle the `neg' operator.  (Bug#19582)
* test/automated/calc-tests.el (calc-tests-equal, calc-tests-simple):
New functions.
(test-calc-remove-units, test-calc-extract-units)
(test-calc-convert-units): New tests.

4 files changed, 79 insertions, 4 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 280f6022007..a2467e6b00f 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,10 @@
+2015-01-22  Wolfgang Jenkner  <wjenkner@inode.at>
+
+	* calc/calc-units.el (math-units-in-expr-p)
+	(math-single-units-in-expr-p, math-find-compatible-unit-rec)
+	(math-extract-units): Handle the `neg' operator.  (Bug#19582)
+	[Backport]
+
 2015-01-21  Daniel Koning  <dk@danielkoning.com>  (tiny change)
 
 	* subr.el (posnp): Correct docstring of `posnp'.
diff --git a/lisp/calc/calc-units.el b/lisp/calc/calc-units.el
index 26a644a29ba..05950864a52 100644
--- a/lisp/calc/calc-units.el
+++ b/lisp/calc/calc-units.el
@@ -904,10 +904,12 @@ If COMP or STD is non-nil, put that in the units table instead."
   (and (consp expr)
        (if (eq (car expr) 'var)
 	   (math-check-unit-name expr)
-	 (and (or sub-exprs
-		  (memq (car expr) '(* / ^)))
-	      (or (math-units-in-expr-p (nth 1 expr) sub-exprs)
-		  (math-units-in-expr-p (nth 2 expr) sub-exprs))))))
+	 (if (eq (car expr) 'neg)
+	     (math-units-in-expr-p (nth 1 expr) sub-exprs)
+	   (and (or sub-exprs
+		    (memq (car expr) '(* / ^)))
+		(or (math-units-in-expr-p (nth 1 expr) sub-exprs)
+		    (math-units-in-expr-p (nth 2 expr) sub-exprs)))))))
 
 (defun math-only-units-in-expr-p (expr)
   (and (consp expr)
@@ -924,6 +926,8 @@ If COMP or STD is non-nil, put that in the units table instead."
   (cond ((math-scalarp expr) nil)
 	((eq (car expr) 'var)
 	 (math-check-unit-name expr))
+	((eq (car expr) 'neg)
+	 (math-single-units-in-expr-p (nth 1 expr)))
 	((eq (car expr) '*)
 	 (let ((u1 (math-single-units-in-expr-p (nth 1 expr)))
 	       (u2 (math-single-units-in-expr-p (nth 2 expr))))
@@ -1079,6 +1083,8 @@ If COMP or STD is non-nil, put that in the units table instead."
 	((eq (car-safe expr) '/)
 	 (or (math-find-compatible-unit-rec (nth 1 expr) pow)
 	     (math-find-compatible-unit-rec (nth 2 expr) (- pow))))
+	((eq (car-safe expr) 'neg)
+	 (math-find-compatible-unit-rec (nth 1 expr) pow))
 	((and (eq (car-safe expr) '^)
 	      (integerp (nth 2 expr)))
 	 (math-find-compatible-unit-rec (nth 1 expr) (* pow (nth 2 expr))))
@@ -1497,6 +1503,8 @@ If COMP or STD is non-nil, put that in the units table instead."
    ((memq (car-safe expr) '(* /))
     (cons (car expr)
           (mapcar 'math-extract-units (cdr expr))))
+   ((eq (car-safe expr) 'neg)
+    (math-extract-units (nth 1 expr)))
    ((eq (car-safe expr) '^)
     (list '^ (math-extract-units (nth 1 expr)) (nth 2 expr)))
    ((math-check-unit-name expr) expr)
diff --git a/test/ChangeLog b/test/ChangeLog
index c31367c6b1a..3f2d761dadd 100644
--- a/test/ChangeLog
+++ b/test/ChangeLog
@@ -1,3 +1,11 @@
+2015-01-22  Wolfgang Jenkner  <wjenkner@inode.at>
+
+	* automated/calc-tests.el (calc-tests-equal, calc-tests-simple):
+	New functions.
+	(test-calc-remove-units, test-calc-extract-units)
+	(test-calc-convert-units): New tests.
+	[Backport]
+
 2014-12-30  Michael Albinus  <michael.albinus@gmx.de>
 
 	* automated/tramp-tests.el (tramp--test-smb-or-windows-nt-p):
diff --git a/test/automated/calc-tests.el b/test/automated/calc-tests.el
index 331e01e4640..d5252ea62a9 100644
--- a/test/automated/calc-tests.el
+++ b/test/automated/calc-tests.el
@@ -27,6 +27,40 @@
 (require 'cl-lib)
 (require 'ert)
 (require 'calc)
+(require 'calc-ext)
+(require 'calc-units)
+
+;; XXX The order in which calc libraries (in particular calc-units)
+;; are loaded influences whether a calc integer in an expression
+;; involving units is represented as a lisp integer or a calc float,
+;; see bug#19582.  Until this will be fixed the following function can
+;; be used to compare such calc expressions.
+(defun calc-tests-equal (a b)
+  "Like `equal' but allow for different representations of numbers.
+For example: (calc-tests-equal 10 '(float 1 1)) => t.
+A and B should be calc expressions."
+  (cond ((math-numberp a)
+	 (and (math-numberp b)
+	      (math-equal a b)))
+	((atom a)
+	 (equal a b))
+	((consp b)
+	 ;; Can't be dotted or circular.
+	 (and (= (length a) (length b))
+	      (equal (car a) (car b))
+	      (cl-every #'calc-tests-equal (cdr a) (cdr b))))))
+
+(defun calc-tests-simple (fun string &rest args)
+  "Push STRING on the calc stack, then call FUN and return the new top.
+The result is a calc (i.e., lisp) expression, not its string representation.
+Also pop the entire stack afterwards.
+An existing calc stack is reused, otherwise a new one is created."
+  (calc-eval string 'push)
+  (prog1
+      (ignore-errors
+	(apply fun args)
+	(calc-top-n 1))
+    (calc-pop 0)))
 
 (ert-deftest test-math-bignum ()
   ;; bug#17556
@@ -34,6 +68,24 @@
     (should (math-negp n))
     (should (cl-notany #'cl-minusp (cdr n)))))
 
+(ert-deftest test-calc-remove-units ()
+  (should (calc-tests-equal (calc-tests-simple #'calc-remove-units "-1 m") -1)))
+
+(ert-deftest test-calc-extract-units ()
+  (should (calc-tests-equal (calc-tests-simple #'calc-extract-units "-1 m")
+			    '(var m var-m)))
+  (should (calc-tests-equal (calc-tests-simple #'calc-extract-units "-1 m*cm")
+			    '(* (float 1 -2) (^ (var m var-m) 2)))))
+
+(ert-deftest test-calc-convert-units ()
+  ;; Used to ask for `(The expression is unitless when simplified) Old Units: '.
+  (should (calc-tests-equal (calc-tests-simple #'calc-convert-units "-1 m" nil "cm")
+			    '(* -100 (var cm var-cm))))
+  ;; Gave wrong result.
+  (should (calc-tests-equal (calc-tests-simple #'calc-convert-units "-1 m"
+					       (math-read-expr "1m") "cm")
+			    '(* -100 (var cm var-cm)))))
+
 (provide 'calc-tests)
 ;;; calc-tests.el ends here