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These functions substitute elements throughout a tree of cons
cells. (See Sequence Functions, for the cl-substitute
function, which works on just the top-level elements of a list.)
This function substitutes occurrences of old with new in tree, a tree of cons cells. It returns a substituted tree, which will be a copy except that it may share storage with the argument tree in parts where no substitutions occurred. The original tree is not modified. This function recurses on, and compares against old, both cars and cdrs of the component cons cells. If old is itself a cons cell, then matching cells in the tree are substituted as usual without recursively substituting in that cell. Comparisons with old are done according to the specified test (
eql
by default). The:key
function is applied to the elements of the tree but not to old.
This function is like
cl-subst
, except that it works by destructive modification (bysetcar
orsetcdr
) rather than copying.
The cl-subst-if
, cl-subst-if-not
, cl-nsubst-if
, and
cl-nsubst-if-not
functions are defined similarly.
This function is like
cl-subst
, except that it takes an association list alist of old-new pairs. Each element of the tree (after applying the:key
function, if any), is compared with the cars of alist; if it matches, it is replaced by the corresponding cdr.