Re: matching a simple string variable
Hi Joe, > > (match (cons '@A (conc (chop Varstring) '(@B))) ... > I'm using your "match" here as a simple string matcher. I'm sure there are > better ways, but I'm happy with my baby steps that appear to work! If you are only interested in a boolean result, but don't need the values of '@A' and '@B', you could of course simply do (sub? Varstring ...) ♪♫ Alex -- UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
Re: matching a simple string variable
Hi Joe, Also note that it's fairly easy to pull in regex functionality, should you need it. See http://rosettacode.org/wiki/Regular_expressions#PicoLisp for an example (pil64).
Re: matching a simple string variable
On Tue, Jan 03, 2017 at 07:52:34AM +0100, Alexander Burger wrote: >(match (append '(@A) (chop Varstring) '(@B)) ... BTW, better is perhaps (match (cons '@A (conc (chop Varstring) '(@B))) ... because 'append' unnecessarily copies the list just built by 'chop'. 'conc' avoids that garbage. Not critical though ;) ♪♫ Alex -- UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
Re: matching a simple string variable
Hi Bruno,
> If you want
> (match '(@A (chop varstring) @B) description)
> to match
> (match '(@A "C" "I" "T" "Y" @B) description)
> you'll have to add a tilde before chop, like this:
> (match '(@A ~(chop varstring) @B) description)
Yes, but this only works if the value of 'varstring' is constant.
> That said, do you think you could keep "CITY" intact inside the list,
> without cutting it into
> its letters? I mean, would
> (match '(@A "CITY" @B) description)
> work for what you want to do?
No, it matches the symbol "CITY". Would succeed if you call
(match '(@A "CITY" @B) '("a" "b" "CITY" "c" "d"))
but not
(match '(@A "CITY" @B) '("a" "b" "C" "I" "T" "Y" "c" "d"))
> Because if it does, then you can write:
> (setq varstring "CITY")
> (match '(@A varstring @B) description)
> which is much simpler than the first solution I gave.
No, this won't work either. As the quoted list is not evaluated, it tries to
match the *atom* 'varstring' which will not be helpful.
♪♫ Alex
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Re: matching a simple string variable
Hi Joe, > (setq varstring "CITY") > (match '(@A (chop varstring) @B) description) > > perhaps the function in the middle of the quote is the problem? Or the extra > list introduced by chop? Yes. The 'chop' call is not evaluated inside the quoted expression. There are two ways to handle it: 1. If the string is constant, you can use a read macro (match '(@A ~(chop "CITY") @B) ... 2. Otherwise you must build the pattern at runtime (match (append '(@A) (chop Varstring) '(@B)) ... ♪♫ Alex -- UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
Re: matching a simple string variable
I think you're right on what's the problem. Chopping the varstring creates
a list of characters,
("C" "I" "T" "Y"), and the final list would look like '(@A ("C" "I" "T"
"Y") @B), which does
not match '(@A "C" "I" "T" "Y" @B) above.
If you want
(match '(@A (chop varstring) @B) description)
to match
(match '(@A "C" "I" "T" "Y" @B) description)
you'll have to add a tilde before chop, like this:
(match '(@A ~(chop varstring) @B) description)
The tilde is a read macro, and it will splice the result into the list. You
can read more about
read macros here: http://software-lab.de/doc/ref.html#macro-io
That said, do you think you could keep "CITY" intact inside the list,
without cutting it into
its letters? I mean, would
(match '(@A "CITY" @B) description)
work for what you want to do?
Because if it does, then you can write:
(setq varstring "CITY")
(match '(@A varstring @B) description)
which is much simpler than the first solution I gave.
On Mon, Jan 2, 2017 at 10:52 PM, Joe Golden wrote:
> I'm trying to do some simple string matching and find match works nicely
> when the string is a literal list of chars like
>
> (match '(@A "C" "I" "T" "Y" @B) description)
>
> but I need to match on a variable string stored in varstring which then
> needs to get chopped (I think). I'm running into problems with
>
> (setq varstring "CITY")
> (match '(@A (chop varstring) @B) description)
>
> perhaps the function in the middle of the quote is the problem? Or the
> extra list introduced by chop?
>
> Any guidance appreciated.
> --
> Joe Golden
> --
> UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
>
matching a simple string variable
I'm trying to do some simple string matching and find match works nicely when the string is a literal list of chars like (match '(@A "C" "I" "T" "Y" @B) description) but I need to match on a variable string stored in varstring which then needs to get chopped (I think). I'm running into problems with (setq varstring "CITY") (match '(@A (chop varstring) @B) description) perhaps the function in the middle of the quote is the problem? Or the extra list introduced by chop? Any guidance appreciated. -- Joe Golden -- UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
