path and += troubles

path and += troubles

[Steven Klass]

Hi all,

	OK after reading the FAQ completely I am at my wits end.  I want to  
create three basic functions dealing with arrays
		- Append
		- Prepend
		- Delete
	
	The basic usage would be something along the lines of let's say I  
had this nice array called path which looked like this:
	
	echo $path
		/usr/sbin	/bin	/foo	/usr/local/bin

Then I did ran a couple of functions..
		appendPath  path /bin
		prependPath path /sbin
		deletePath path /foo

and ended up with...

	echo $path
		/sbin /usr/sbin /usr/local/bin /bin


My basic functions would be:

	appendPath() {
		# if the path exists delete it..
		deletePath $1 $2
		# Append the path to the end..
		$1+=($2)
	}

	deletePath () {
   		# I cannot take credit for this - Borrowed from the net - but it  
works :)
		# I couldn't figure out how to use ${var#del}
		local element
   		local build
   		build=()
   		eval '
   			foreach element in "$'"$1"'[@]"
   			do
     				if [[ -d "$element" && "$element" != $2 ]]
     				then
       					build=("$build[@]" "$element")
     				fi
   			done
   			'"$1"'=( "$build[@]" )
   		'
	}

But THIS DOESN"T WORK!!!  IT Should!!  According to the FAQ += should  
add the path to the array.  Can someone help me with 2 things.
	1.  Why does += not work when adding to the array - It should right?
	2.  How will I handle prepend - I need to do a shift of all array items

Comments welcome thanks!!

---

Steven Klass

sklass@pointcircle.com
(480) 988-5657

Re: path and += troubles

[Christian Taylor]

Steven Klass wrote:
> Hi all,
>
> 	OK after reading the FAQ completely I am at my wits end.  I want to
> create three basic functions dealing with arrays
> 		- Append
> 		- Prepend
> 		- Delete

I don't know if this is exactly what you're looking for, but I think you can 
save yourself some work by just using direct operations.

Prepending/Appending:
path=( prepended $path appended )

I never bothered about a deletion function, because I simply use:
typeset -U path
which will keep only the first occurence of any element.

Hope this is of some help,

Christian

Re: path and += troubles

[Vincent Lefevre]

On 2005-11-26 10:32:35 +0100, Christian Taylor wrote:
> I never bothered about a deletion function, because I simply use:
> typeset -U path
> which will keep only the first occurence of any element.

But if a same path is written in two different ways, it doesn't
recognise it:

ay:~> echo $library_path
/home/lefevre/./lib /home/lefevre/./lib /home/lefevre/lib /usr/local/gmp/lib
ay:~> typeset -U LIBRARY_PATH
ay:~> echo $library_path
/home/lefevre/./lib /home/lefevre/lib /usr/local/gmp/lib

-- 
Vincent Lefèvre <vincent@vinc17.org> - Web: <http://www.vinc17.org/>
100% accessible validated (X)HTML - Blog: <http://www.vinc17.org/blog/>
Work: CR INRIA - computer arithmetic / SPACES project at LORIA

Re: path and += troubles

[Steven Klass]

Hi,

This exposes one of my personal problems with typeset.  If I really  
want a path appended typeset -U will drop the appended path, in favor  
of the path which already exists.  So IMHO the only way to handle  
this properly is to
	
	Normalize the new path ($2) - Remove any trailing slashes ensure no  
double-slashes
	Check to see if the new path exists in the old path array ($1) and  
delete it
	Append or Prepend the new path to the $1
	
Here's some of the cleanup stuff I read about in this list..
	path=($^path(N))
	setopt EXTENDED_GLOB
	path=(${${path//\/##/\/}%/})
	unsetopt EXTENDED_GLOB
	typeset -U path

But can anyone please explain my number 1 item - that is really  
annoying me..

	appendPath() {
		# if the path exists delete it..
		deletePath $1 $2
		# Append the path to the end..
		$1+=($2)
	}

	1.  Why does += not work when adding to the array - It should right?


---

Steven Klass

sklass@pointcircle.com
(480) 988-5657

On Nov 26, 2005, at 6:25 AM, Vincent Lefevre wrote:

> On 2005-11-26 10:32:35 +0100, Christian Taylor wrote:
>> I never bothered about a deletion function, because I simply use:
>> typeset -U path
>> which will keep only the first occurence of any element.
>
> But if a same path is written in two different ways, it doesn't
> recognise it:
>
> ay:~> echo $library_path
> /home/lefevre/./lib /home/lefevre/./lib /home/lefevre/lib /usr/ 
> local/gmp/lib
> ay:~> typeset -U LIBRARY_PATH
> ay:~> echo $library_path
> /home/lefevre/./lib /home/lefevre/lib /usr/local/gmp/lib
>
> -- 
> Vincent Lefèvre <vincent@vinc17.org> - Web: <http://www.vinc17.org/>
> 100% accessible validated (X)HTML - Blog: <http://www.vinc17.org/ 
> blog/>
> Work: CR INRIA - computer arithmetic / SPACES project at LORIA

Re: path and += troubles

[Bart Schaefer]

On Nov 25,  9:32pm, Steven Klass wrote:
}
} 		# Append the path to the end..
} 		$1+=($2)

As you've discovered, this won't work.  $1 is not an identifier (it's an
identifier dereference) so $1+= is not an assignment.  Of course, you
need to have a recent-enough version of zsh to support += assignments.

For some reason "setopt nullglob" (even cshnullglob) prevents the error
message that would otherwise be produced for this line, turning it into
a silent no-op.  I think that's probably an obscure bug.

Anyway, what you need is something like

		eval $1'+=( $2 )'

} 		# I couldn't figure out how to use ${var#del}

That's probably because it's ${var:#del}.

		eval $1'=( ${(P)1:#$2} )'

} 	2.  How will I handle prepend - I need to do a shift

		eval $1'=( $2 ${(P)1} )'

or (better only for really huge arrays, and watch out for the ksharrays
setopt which changes the subscript offset):

		eval $1'[1]=( $2 ${${(P)1}[1]} )'

You're probably better off doing everything in one assignment rather than
by having appendPath call deletePath.  E.g.

    appendElem() { eval $1'+=( $2 )' }
    prependElem() { eval $1'=( $2 ${(P)1} )' }
    deleteElem() {  eval $1'=( ${(P)1:#$2} )' }
    appendUniq() { eval $1'=( ${(P)1:#$2} $2 )' }
    prependUniq() { eval $1'=( $2 ${(P)1:#$2} )' }

Re: path and += troubles

[Vincent Lefevre]

On 2005-11-26 07:54:35 -0700, Steven Klass wrote:
> Here's some of the cleanup stuff I read about in this list..
> 	path=($^path(N))
> 	setopt EXTENDED_GLOB
> 	path=(${${path//\/##/\/}%/})
> 	unsetopt EXTENDED_GLOB
> 	typeset -U path

This is a bad idea if the user has EXTENDED_GLOB set. Isn't it
possible to turn on EXTENDED_GLOB locally in parameter expansion?

> But can anyone please explain my number 1 item - that is really  
> annoying me..
> 
> 	appendPath() {
> 		# if the path exists delete it..
> 		deletePath $1 $2
> 		# Append the path to the end..
> 		$1+=($2)
> 	}
> 
> 	1.  Why does += not work when adding to the array - It should right?

$1+=($2) doesn't make sense IMHO. You probably need an eval.

-- 
Vincent Lefèvre <vincent@vinc17.org> - Web: <http://www.vinc17.org/>
100% accessible validated (X)HTML - Blog: <http://www.vinc17.org/blog/>
Work: CR INRIA - computer arithmetic / SPACES project at LORIA