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.

2 files changed, 18 insertions, 4 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index b7a38af9609..150f32f351a 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,9 @@
+2015-01-15  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)
+
 2015-01-15  Stefan Monnier  <monnier@iro.umontreal.ca>
 
         * emacs-lisp/eieio-core.el: Provide support for cl-generic.
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)