Add `acdw/system' macro

`acdw/system' eases configuration -- it returns the system when called with no
arguments, acts as a test with one argument, or as a `pcase' with more than one
argument.

1 files changed, 26 insertions, 9 deletions

@@ -21,12 +21,29 @@
 
 ;;; Variables
 
-(defconst acdw/system (pcase system-type
-                        ('gnu/linux :home)
-                        ((or 'msdos 'windows-nt) :work)
-                        (_ :other))
+(defconst acdw/system
+  (pcase system-type
+    ('gnu/linux :home)
+    ((or 'msdos 'windows-nt) :work)
+    (_ :other))
   "Which computer system is currently being used.")
 
+(defmacro acdw/system (&rest arg)
+  "Convenience macro for interfacing with `acdw/system'.
+
+When called without arguments, it returns `acdw/system'.
+When called with one argument, it returns (eq acdw/system ARG).
+When called with multiple arguments, it returns `pcase' over each argument."
+  (cond
+   ((not arg) acdw/system)
+   ((not (cdr arg))
+    `(when (eq acdw/system ,(car arg))
+       ,(car arg)))
+   ((cdr arg)
+    `(pcase acdw/system
+       ,@arg))
+   (t (error "Wrong argument type: %s" (type-of arg)))))
+
 
 ;;; Utility functions
 ;; I don't prefix these because ... reasons.  Honestly I probably should prefix
@@ -162,11 +179,11 @@ if MAKE-DIRECTORY is non-nil."
 
 (defun acdw/find-emacs-source ()
   "Find where Emacs keeps its source tree."
-  (pcase acdw/system
-    (:work (expand-file-name
-            (concat "~/src/emacs-" emacs-version "/src")))
-    (:home (expand-file-name "~/src/pkg/emacs/src/emacs-git/src"))
-    (:other nil)))
+  (acdw/system
+   (:work (expand-file-name
+           (concat "~/src/emacs-" emacs-version "/src")))
+   (:home (expand-file-name "~/src/pkg/emacs/src/emacs-git/src"))
+   (:other nil)))
 
 (defun acdw/gc-disable ()
   "Functionally disable the Garbage collector."