Add separate day/month formatting module.

src/cal-format.scm

@@ -0,0 +1,46 @@
+;;
+;; cal-format.scm
+;;
+;; Calendar structures formatting.
+;;
+;; ISC License
+;;
+;; Copyright 2023 Brmlab, z.s.
+;; Dominik Pantůček <dominik.pantucek@trustica.cz>
+;;
+;; Permission to use, copy, modify, and/or distribute this software
+;; for any purpose with or without fee is hereby granted, provided
+;; that the above copyright notice and this permission notice appear
+;; in all copies.
+;; 
+;; THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
+;; WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
+;; WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
+;; AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR
+;; CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
+;; OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
+;; NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+;; CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+;;
+
+(declare (unit cal-format))
+
+(module
+ cal-format
+ (
+  cal-format
+  )
+
+ (import scheme
+	 cal-day
+	 cal-month)
+
+ ;; Formats day or month or #f to string.
+ (define (cal-format v)
+   (if (cal-day? v)
+       (cal-day->string v)
+       (if (cal-month? v)
+	   (cal-month->string v)
+	   "--")))
+
+ )