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+;;;; lambda-tools.lisp
+
+(in-package #:lambda-tools)
+
+(defun $or (&rest predicates)
+  "Each argument in PREDICATES is a predicate function of one
+argument. Returns a new predicate, call it P, that is the
+disjunction of each of the PREDICATES.
+
+The value of (P X) is the value of the first predicate Q in PREDICATES
+such that (Q X) is non-NIL, or is NIL if none of the PREDICATES return
+non-NIL.
+
+That is, the disjuction of PREDICATES is short-circuiting. If any
+PREDICATES have side effects, they will be executed only if each of
+the preceding predicates in the list returned NIL."
+  (labels ((disj (x preds)
+             (if (null preds) nil
+                 (if-let (res (funcall (car preds) x))
+                   res
+                   (disj x (cdr preds))))))
+    (lambda (x) (disj x predicates))))
+
+(defun $and (&rest predicates)
+  "Each argument in PREDICATES is a predicate function of one
+argument. Returns a new predicate of one argument, call it P, that is
+the conjunction of each of the PREDICATES.
+
+The value of (P X) is NIL if any of the PREDICATES applied to X are
+NIL. Otherwise it is the value of the last member in PREDICATES
+applied to X.
+
+That is, the conjunction of PREDICATES is short-circuiting.  If any
+PREDICATES have side effects, they will be executed only if each of
+the preceding predicates in the list returned non-NIL."
+  (labels ((conj (x preds)
+             (cond ((null preds) t)
+                   ((null (cdr preds)) (funcall (car preds) x))
+                   ((funcall (car preds) x)
+                    (conj x (cdr preds))))))
+    (lambda (x) (conj x predicates))))