Node:Sorting, Next:Files List, Previous:Prepare the data, Up:Prepare the data
Emacs contains a function to sort lists, called (as you might guess)
sort. The sort function takes two arguments, the list
to be sorted, and a predicate that determines whether the first of
two list elements is "less" than the second.
As we saw earlier (see Using the Wrong Type Object as an Argument), a predicate is a function that
determines whether some property is true or false. The sort
function will reorder a list according to whatever property the
predicate uses; this means that sort can be used to sort
non-numeric lists by non-numeric criteria--it can, for example,
alphabetize a list.
The < function is used when sorting a numeric list. For example,
(sort '(4 8 21 17 33 7 21 7) '<)
produces this:
(4 7 7 8 17 21 21 33)
(Note that in this example, both the arguments are quoted so that the
symbols are not evaluated before being passed to sort as
arguments.)
Sorting the list returned by the
recursive-lengths-list-many-files function is straightforward;
it uses the < function:
(sort
(recursive-lengths-list-many-files
'("../lisp/macros.el"
"../lisp/mailalias.el"
"../lisp/makesum.el"))
'<
which produces:
(85 86 116 122 154 176 179 265)
(Note that in this example, the first argument to sort is not
quoted, since the expression must be evaluated so as to produce the
list that is passed to sort.)