Added more (if-some) utility

tk/listlogic.scm

@@ -2,7 +2,8 @@
   #:export (flatten
             lp&
             l&
-            if-some)
+            if-some
+            if-some-else)
   #:duplicates (warn-override-core warn ))
 
 (define (flatten-helper lst acc stk)
@@ -48,3 +49,7 @@
 ;; Returns the argument if it isn't #f, otherwise returns the empty list
 (define (if-some $cond)
   (if $cond $cond '()))
+
+;; Returns the first argument if it isn't #f, otherwise returns the second.
+(define (if-some-else $cond $else)
+  (if $cond $cond $else))