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Re: Re[4]: [Orgmode] programming for org-mode
From: |
David Maus |
Subject: |
Re: Re[4]: [Orgmode] programming for org-mode |
Date: |
Sun, 08 Aug 2010 08:43:07 +0200 |
User-agent: |
Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (Gojō) APEL/10.8 Emacs/23.2 (i486-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) |
Ivanov Dmitry wrote:
>Thanks, David. I improved the scheme, added 2 question. Please, take a look.
1/
,----
| 09. (if (or (equal "(" (substring prop 0 1)) (equal "'"
(substring prop 0 1)))
|
| vs.
|
| 09. (if (string-match "^'?(.*)$" prop)
`----
I wouldn't call it a flaw in the original check but a pragmatic
solution for the problem at this point. Ideally we want to check if
`prop' is a lisp expression so we can call `read' to return the
expression as lisp object. To achieve this we would need a function
that checks if the string `prop' is a valid s-expression[1]: Balanced
parentheses and valid lisp atoms. I am not an expert in regular
expressions but I think such a check can't be done with regexps but
requires an implementation of a lisp parser.
Example: (string-match "^'?(.*)$" "((foo baz)")) would return t but
"((foo baz)" is not a valid s-expression.
If we want (read prop) not to fail on an invalid s-exp but to threat
them as strings we can try to catch the error when executing `read':
,----
| (condition-case nil
| (read prop)
| (error prop))
`----
This would return the lisp object for `prop' if `prop' is a valid lisp
expression and the string `prop' otherwise (C-h f condition-case RET).
2/
,----
| 13. (progn (set-text-properties 0 (length prop) nil prop)
| 14. prop)))
`----
Setting the text-properties to nil indeed removes all
... text-properties, including colors. The `progn' is unnecessary
because the body of the else clause is not limited to one lisp
expression (C-h f if RET).
HTH,
-- David
[1] Note that the terms "s-expression", "lisp-expression", and "lisp
object" refer to one and the same structure.
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