`format-time' can now do sub-second times

* doc/lispref/os.texi (Time Parsing): Document it.

* lisp/calendar/time-date.el (format-seconds): Allow formatting
sub-second times.

doc/lispref/os.texi

@@ -1901,7 +1901,10 @@ The integer number of hours.
 The integer number of minutes.
 @item %s
 @itemx %S
-The integer number of seconds.
+The number of seconds.  If the optional @samp{,} parameter is used,
+it's a floating point number, and the number after the @samp{,}
+specifies how many decimals to be used.  @samp{%,2s} means ``use two
+decimals''.
 @item %z
 Non-printing control flag.  When it is used, other specifiers must be
 given in the order of decreasing size, i.e., years before days, hours

etc/NEWS

@@ -1204,6 +1204,11 @@ list.
 
 ** Miscellaneous
 
++++
+*** 'format-seconds' can now be used for sub-second times.
+The new optional "," parameter has been added, and
+(format-seconds "%mm %,1ss" 66.4) will now result in "1m 6.4s".
+
 ---
 *** 'global-display-fill-column-indicator-mode' skips some buffers.
 By default, turning on 'global-display-fill-column-indicator-mode'

lisp/calendar/time-date.el

@@ -278,6 +278,10 @@ Lower-case specifiers return only the unit.
 optional leading \".\" for zero-padding.  For example, \"%.3Y\" will
 return something of the form \"001 year\".
 
+The \"%s\" spec takes an additional optional parameter,
+introduced by the \",\" character, to say how many decimals to
+use.  \"%,1s\" means \"use one decimal\".
+
 The \"%z\" specifier does not print anything.  When it is used, specifiers
 must be given in order of decreasing size.  To the left of \"%z\", nothing
 is output until the first non-zero unit is encountered."
@@ -289,10 +293,11 @@ is output until the first non-zero unit is encountered."
                  ("s" "second"        1)
                  ("z")))
         (case-fold-search t)
-        spec match usedunits zeroflag larger prev name unit num zeropos)
+        spec match usedunits zeroflag larger prev name unit num zeropos
-    (while (string-match "%\\.?[0-9]*\\(.\\)" string start)
+        fraction)
+    (while (string-match "%\\.?[0-9]*\\(,[0-9]\\)?\\(.\\)" string start)
       (setq start (match-end 0)
-            spec (match-string 1 string))
+            spec (match-string 2 string))
       (unless (string-equal spec "%")
         (or (setq match (assoc (downcase spec) units))
             (error "Bad format specifier: `%s'" spec))
@@ -307,12 +312,17 @@ is output until the first non-zero unit is encountered."
         (push match usedunits)))
     (and zeroflag larger
          (error "Units are not in decreasing order of size"))
-    (setq seconds (time-convert seconds 'integer))
+    (unless (numberp seconds)
+      (setq seconds (float-time seconds)))
+    (setq fraction (mod seconds 1)
+          seconds (round seconds))
     (dolist (u units)
       (setq spec (car u)
             name (cadr u)
             unit (nth 2 u))
-      (when (string-match (format "%%\\(\\.?[0-9]+\\)?\\(%s\\)" spec) string)
+      (when (string-match
+             (format "%%\\(\\.?[0-9]+\\)?\\(,[0-9]+\\)?\\(%s\\)" spec)
+             string)
         (if (string-equal spec "z")     ; must be last in units
             (setq string
                   (replace-regexp-in-string
@@ -327,9 +337,23 @@ is output until the first non-zero unit is encountered."
               (setq zeropos (unless (zerop num) (match-beginning 0))))
           (setq string
                 (replace-match
-                 (format (concat "%" (match-string 1 string) "d%s") num
+                 (format (if (match-string 2 string)
-                         (if (string-equal (match-string 2 string) spec)
+                             (concat
-                             ""       ; lower-case, no unit-name
+                              "%"
+                              (and (match-string 1 string)
+                                   (if (= (elt (match-string 1 string) 0) ?.)
+                                       (concat "0" (substring
+                                                    (match-string 1 string) 1))
+                                     (match-string 1 string)))
+                              (concat "." (substring
+                                           (match-string 2 string) 1))
+                              "f%s")
+                           (concat "%" (match-string 1 string) "d%s"))
+                         (if (= unit 1)
+                             (+ num fraction)
+                           num)
+                         (if (string-equal (match-string 3 string) spec)
+                             ""         ; lower-case, no unit-name
                            (format " %s%s" name
                                    (if (= num 1) "" "s"))))
                  t t string))))))

test/lisp/calendar/time-date-tests.el

@@ -81,7 +81,14 @@
 (ert-deftest test-format-seconds ()
   (should (equal (format-seconds "%y %d %h %m %s %%" 0) "0 0 0 0 0 %"))
   (should (equal (format-seconds "%y %d %h %m %s %%" 9999999) "0 115 17 46 39 %"))
-  (should (equal (format-seconds "%y %d %h %m %z %s %%" 1) " 1 %")))
+  (should (equal (format-seconds "%y %d %h %m %z %s %%" 1) " 1 %"))
+  (should (equal (format-seconds "%mm %ss" 66) "1m 6s"))
+  (should (equal (format-seconds "%mm %5ss" 66) "1m     6s"))
+  (should (equal (format-seconds "%mm %.5ss" 66.4) "1m 00006s"))
+
+  (should (equal (format-seconds "%mm %,1ss" 66.4) "1m 6.4s"))
+  (should (equal (format-seconds "%mm %5,1ss" 66.4) "1m   6.4s"))
+  (should (equal (format-seconds "%mm %.5,1ss" 66.4) "1m 006.4s")))
 
 (ert-deftest test-ordinal ()
   (should (equal (date-ordinal-to-time 2008 271)