Re: replacing a function with another one

[lee <lee@yun.yagibdah.de>]

Michael Heerdegen <michael_heerdegen@web.de> writes:

> lee <lee@yun.yagibdah.de> writes:
>
>> and it doesn´t work because end-marker is undefined despite I just
>> defined it :(  So I have
>>
>>
>>     (let ((end-marker (concat "^" comment-start lsl-hi-lock-patterns-end-marker)))
>>       (let ((marker-pos (re-search-forward end-marker (point-max) t)))
>>       (do-something)))
>>
>
> The functionality you want, and that you reached with the nested `let',
> is exactly what `let*' does.  When I was learning LISP, I was also
> confused about `let'.  Standard `let' first evaluates all
> expressions, then binds the variables, so in works "parallel" - see

Ah!  Finally I understand what the difference is!  What is the point of
having two variations of `let'?


> [...]
>> 	  (let ((patterns nil))
>> 	    (while (< (point) marker-pos)
>> 	      (setq patterns (append (read (current-buffer)) patterns)))
>> 	    (setq patterns patterns)))))))
>>
>>
>> I need this function to return `patterns'.  Without the last line, it
>> seems to return nil because the setq is enclosed in the while.
>
> `let' returns the value returned by the last body expression (in
> particular, that isn't necessarily the value of the variable `patterns'
> in your example!).  And `while' always returns nil (strictly speaking,
> the return value isn't documented, so don't rely on it at all).  So this
> is what you want:
>
>  	  (let ((patterns nil))
>  	    (while (< (point) marker-pos)
>  	      (setq patterns (append (read (current-buffer)) patterns)))
>  	    patterns)

Thank you --- I only found that out yesterday.  It makes sense when you
think that a symbol stands for itself --- which is probably not correct,
but I just think of it as that the variable stands for itself and can be
returned like that.


-- 
Knowledge is volatile and fluid.  Software is power.