compat: Add 'sort' for Mes.

* gash/compat.scm [mes] (sort): New procedure.

gash/compat.scm

@@ -107,7 +107,8 @@
           thunk?
           EXIT_SUCCESS
           EXIT_FAILURE
-          exact-integer?)
+          exact-integer?
+          sort)
 
   (define-macro (define-inlinable . rest)
     `(define ,@rest))
@@ -241,4 +242,33 @@
   (define EXIT_FAILURE 1)
 
   ;; Mes only has exact integers.
-  (define exact-integer? integer?))
+  (define exact-integer? integer?)
+
+  ;; A simple (slow!) sort procedure.  It's needed for globbing.
+  (define (sort items less)
+    (define (split-reverse lst)
+      (let loop ((lst lst) (acc1 '()) (acc2 '()))
+        (cond
+         ((null? lst) (values acc1 acc2))
+         ((null? (cdr lst)) (values (cons (car lst) acc1) acc2))
+         (else (loop (cddr lst)
+                     (cons (car lst) acc1)
+                     (cons (cadr lst) acc2))))))
+
+    (define (merge alist blist less)
+      (let loop ((alist alist) (blist blist) (acc '()))
+        (cond
+         ((null? alist) (reverse (append-reverse blist acc)))
+         ((null? blist) (reverse (append-reverse alist acc)))
+         (else (let ((a (car alist))
+                     (b (car blist)))
+                 (if (less a b)
+                     (loop (cdr alist) blist (cons a acc))
+                     (loop alist (cdr blist) (cons b acc))))))))
+
+    (cond
+     ((null? items) items)
+     ((null? (cdr items)) items)
+     (else (call-with-values (lambda () (split-reverse items))
+             (lambda (alist blist)
+               (merge (sort alist less) (sort blist less) less)))))))