Fixed subtraction regression; added new subtraction unit test.

lisp/documentation.lisp

@@ -1,4 +1,9 @@
-(set! documentation (lambda (name)
-    (:documentation  (meta name))))
+(set! documentation (lambda (object)
+    (cond ((= (type object) "LMDA") 
+            (let (d (nth 3 (source object)))
+                (cond ((string? d) d)
+                    (t (source object)))))
+        ((member (type object) '("FUNC" "SPFM"))
+            (:documentation (meta object))))))
 
 (set! doc documentation)

lisp/greaterp.lisp

@@ -1,3 +1,3 @@
 (set! > (lambda (a b)
-
-)
+    "`(> a b)`: Return `t` if `a` is a number greater than `b`, else `nil`."
+    (not (negative? (- a b)))))

lisp/member.lisp

@@ -1,3 +1,5 @@
+(set! nil? (lambda (o) (= o nil)))
+
 (set! member (lambda
             (item collection)
             "Return `t` if this `item` is a member of this `collection`, else `nil`."