diff options
Diffstat (limited to 'lib.functions.lisp')
| -rw-r--r-- | lib.functions.lisp | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/lib.functions.lisp b/lib.functions.lisp index 8eb2304..e3b3180 100644 --- a/lib.functions.lisp +++ b/lib.functions.lisp @@ -28,11 +28,28 @@ each member is STEP distance apart." :collect i))) (fn parse-integer* (inp) (-> (string) (or integer list)) + "Given string INP, attempt to parse an integer. Return NIL otherwise." (parse-integer inp :junk-allowed t)) (fn take (n lst) (-> (fixnum list) list) + "Return the first N elements of LST." (subseq lst 0 n)) (fn split (n lst) (-> (fixnum list) list) + "Return CONS where CAR is the first N elements of LST and CDR is the rest." (cons (take n lst) (subseq lst n))) + +(fn rev-map (indicator lst &key (key-eq #'eq)) + (-> (function list &key (:key-eq function)) list) + "Given LST and INDICATOR: LST -> A, return an association list A -> 2^LST +where key x in A has associations {y in LST : INDICATOR(y) = x}." + (loop :with assoc-list := nil + :for element :in lst + :for key = (funcall indicator element) + :if (assoc key assoc-list :test key-eq) + :do (setf (alist-val key assoc-list) + (cons element (alist-val key assoc-list))) + :else + :do (setq assoc-list (acons key element assoc-list)) + :finally (return assoc-list))) |