Introduce development support function "stub"

sucl/basic.dcl

@@ -176,5 +176,8 @@ showtriple :: !.(.a -> .String) !.(.b -> .String) !.(.c -> .String) !(.a,.b,.c)
 // `Split sep' splits a list into a list of sublists which are separated by `sep'.
 split :: a -> .(.[a] -> [.[a]]) | == a
 
+// `Stub modulename functionname message' aborts with a explanatory message
+stub :: .String .String .String -> a
+
 // `Superset xs ys' determines whether ys is a superset (actually, super-multi-set or super-list) of xs.
 superset :: .[a] -> .(.[a] -> Bool) | == a

sucl/basic.icl

@@ -255,5 +255,10 @@ split sep
           =   ([x:ys],yss)
               where (ys,yss) = spl xs
 
+// `Stub modulename functionname message' aborts with a explanatory message
+stub :: .String .String .String -> a
+stub modulename functionname message
+= abort (modulename+++": "+++functionname+++": "+++message)
+
 superset :: .[a] -> .(.[a] -> Bool) | == a
 superset set = isEmpty o (removeMembers set)