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RE: I'd like to marry while and mapcar...
From: |
Drew Adams |
Subject: |
RE: I'd like to marry while and mapcar... |
Date: |
Fri, 6 Feb 2015 14:49:18 -0800 (PST) |
FWIW, what you wrote in the first place, Marcin, is pretty
much what I would do. Call it Fortranesque, if you like.
But it's classic Lispiness, IMO. Lisp is not Haskell.
This is what I would do:
(let ((includes ())
include)
(while (setq include (get-TeX-macro-arguments "include"))
(push include includes))
(setq includes (nreverse includes)))
I wouldn't bother with `(cl-)loop' or `mapcar' or `mapc' here.
Since you have a function that gets the next thingie you want,
and it returns nil when there are no more, there is no reason
at all to use `catch'+`throw' here.
`catch'+`throw' is useful when, e.g., you have an existing
list that you iterate over (e.g., using `dolist'), and you
do not want to continue iterating over the rest of that
list as soon as you know that you no longer need to.
Here is a typical, end-the-looping-early use of `catch'+`throw':
(defun take (n xs)
"Return a new list containing only the first N elements of list XS.
If N is greater than the length of XS, return (a copy of) XS."
(let ((takes ()))
(catch 'take
(dolist (x xs)
(when (>= (length takes) n) (throw 'take takes))
(push x takes)))
(setq takes (nreverse takes))))
Or if you don't want the inefficiency of evaluating `length'
at each iteration, add a counter:
(defun take (n xs)
"..."
(let ((takes ())
(len 0))
(catch 'take
(dolist (x xs)
(when (>= len n) (throw 'take takes))
(push x takes)
(cl-incf len)))
(setq takes (nreverse takes))))