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Re: Can el-search-query-replace replace mapcar with --map ?

From: Michael Heerdegen
Subject: Re: Can el-search-query-replace replace mapcar with --map ?
Date: Fri, 22 Dec 2017 18:17:57 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux)

Chunyang Xu <> writes:

> It gives me:
>   (--map
>    (* x x)
>    '(1 2 3))

which is expected, of course.

The transformation you want is not trivial, and there are some
problematic cases when it gets complicated - e.g. when the mapped lambda
uses in its body a local variable with the same name as the argument
variable, like in
#+begin_src emacs-lisp
  (lambda (x) (let ((x (1+ x))) (* x x)))

But that should be corner cases in practice.

I would define a helper function to perform the renaming of the lambda
argument into "it" - something like

#+begin_src emacs-lisp
(defun transform-lambda-form-for---map (lambda-form)
  (pcase-let ((`(lambda (,var) . ,body) lambda-form))
     `(cl-symbol-macrolet ((,var it))

and then el-search-query-replace with the rule

#+begin_src emacs-lisp
`(mapcar ,lambda-form ,list)
`(--map ,(transform-lambda-form-for---map lambda-form) ,list)

Does that work ok for you?



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