Function: FCHAIN

Documentation

uses fn-comb to a list of values returned by fns, where every fn in fns is called with x e.g. (fchain (lambda (x y) (and x y)) f1 f2 ... fn) creates a function like: (lambda (x) (and (f1 x) (f2 x) ... (fn x))) in truth it is more like: (lambda (x) (and (f1 x) ((lambda (y) (and (f2 y) (...) y)) x))) works similiar to (defun freduce (fn-comb fn &rest fns) (lambda (arg) (reduce (lambda (x fn-y) (funcall fn-comb x (funcall fn-y arg))) fns :initial-value (funcall fn arg)))) but builds one in comparison to freduce, fchain builds up a big function when called first instead of reducing on the list of functions.

Source

(defun fchain (fn-comb fn &rest fns)
  "uses fn-comb to a list of values returned by fns, where
   every fn in fns is called with x
   e.g. (fchain (lambda (x y) (and x y)) f1 f2 ... fn)
        creates a function like: 
          (lambda (x)
            (and (f1 x)
                 (f2 x)
                 ...
                 (fn x)))
        in truth it is more like:
          (lambda (x)
            (and (f1 x)
                 ((lambda (y) (and (f2 y)
                                   (...) y))
                  x)))

    works similiar to 
      (defun freduce (fn-comb fn &rest fns)
        (lambda (arg)
          (reduce (lambda (x fn-y)
 	      (funcall fn-comb
		       x
		       (funcall fn-y arg)))
	      fns :initial-value (funcall fn arg))))
    but builds one in comparison to freduce, fchain builds
    up a big function when called first instead of reducing on the list
    of functions.
"
  (if (null fns)
      fn
      (let ((chain (apply #'fchain fn-comb fns)))
	(lambda (x)
	  (funcall fn-comb
		   (funcall fn x)
		   (funcall chain x))))))