Re: How to shadow a function temporarily? (flet and cl-flet)

[Alex Kost]

Stefan Monnier (2014-01-26 18:50 +0400) wrote:

>> 1. The main question is: how can I override a function with another
>> compatible function (with the same args) temporarily?
>
> Be careful with "temporarily": it can be interpreted as "lexically" or
> "dynamically".  From your example, it seems you want "dynamically".
> Note, tho, that
>
>    (defun 8+ (arg)
>      (+ 8 arg))
>
>    (flet ((+ (&rest args)
>              (apply '- args)))
>      (8+ 3))                               ; => 5
>
> will give you 11 when byte-compiled.

Thank you, I didn't know about that.

> IOW, you had better look for
> another solution to your problem.  One option could be something along
> the following lines:
>
>    (defvar my-plus-is-subtraction nil)
>
>    (defun 8+ (arg)
>      (funcall (if my-plus-is-subtraction #'- #'+) 8 arg))
>
>    (let ((my-plus-is-subtraction t))
>      (8+ 3))                               ; => 5

It was an example, I cannot modify `8+' function.

Here is what I actiually need: I want to make `read-color' function to
use my functions instead of `foreground-color-at-point' and
`background-color-at-point', so I tried the following (but now I see
that it's not suitable):

binmT2KlAv1lO.bin
Description: application/emacs-lisp

Now i don't see another solution except of using the code of
`read-color' in `my-read-color'.