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2004-01-30T06:14:03-04:00

From my tests, variable substitutions seem to be on exact par with command substitutions.

You're right..it doesn't matter much. And sometimes performance even gets worse with command substitution (because of the way it's compiled).

(except for those command substitutions which also involve variable substitutions at the same time, of course)

You mean when you take advantage of the fact that some commands both alter a variable and return the new value? ...That pretty much goes without saying (one less substitution to perform)

Statistics: Posted by user — Fri Jan 30, 2004 6:14 am

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2004-01-29T22:20:52-04:00

heh. I guess we can agree, like most things, it's a trade off of memory vs performance.
Yeah...it seems most tcl versions are faster at setting the value to an empty string instead of deleting the entire variable, so I guess I should make it
Code:
foreach word [split [set str][set str ""] $splitChr] {...}
And to make it even faster I could replace all variable substitutions with [set ..], but then the code will be much harder to read.

From my tests, variable substitutions seem to be on exact par with command substitutions. (except for those command substitutions which also involve variable substitutions at the same time, of course).

Statistics: Posted by strikelight — Thu Jan 29, 2004 10:20 pm

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2004-01-29T06:35:32-04:00

heh. I guess we can agree, like most things, it's a trade off of memory vs performance.

Yeah...it seems most tcl versions are faster at setting the value to an empty string instead of deleting the entire variable, so I guess I should make it

Code:

foreach word [split [set str][set str ""] $splitChr] {...}

And to make it even faster I could replace all variable substitutions with [set ..], but then the code will be much harder to read.

Statistics: Posted by user — Thu Jan 29, 2004 6:35 am

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2004-01-28T20:48:19-04:00

How long is the string you're testing it with? To be on-topic it should be > 445 bytes
Oh..and what's the point of 'i'?

It was 271 bytes....
Now it is:

Code:

% string bytelength $mylist547

'i' just gives the procs something to do to simulate that they are doing something meaningful ;x

Code:

% time {a $mylist} 1000305 microseconds per iteration% time {b $mylist} 1000391 microseconds per iteration% time {a $mylist} 1000277 microseconds per iteration% time {b $mylist} 1000336 microseconds per iteration

So it's STILL ~20% - ~30% increase.

heh. I guess we can agree, like most things, it's a trade off of memory vs performance.

Statistics: Posted by strikelight — Wed Jan 28, 2004 8:48 pm

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2004-01-28T20:38:32-04:00

How long is the string you're testing it with? To be on-topic it should be > 445 bytes
Oh..and what's the point of 'i'?

Statistics: Posted by user — Wed Jan 28, 2004 8:38 pm

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2004-01-28T20:36:21-04:00

Code:
% proc a {mylist} {set i 0; foreach word $mylist {incr i}}% proc b {mylist} {set i 0; foreach word [set mylist][unset mylist] {incr i}
Your test is not fair, as 'unset' returns an empty STRING, making the list before it become a string that has to be translated back to a list by foreach
try this instead and you'll see the unset adds very little to the total cpu usage
Code:
proc a it {set i 0; foreach word [split $it] {incr i}; set i}proc b it {set i 0; foreach word [split [set it][unset it]] {incr i}; set i}

You are correct...

Code:

% proc b {mylist} {set i 0; foreach word [split [set mylist][unset mylist]] {incr i}}% proc a {mylist} {set i 0; foreach word [split $mylist] {incr i}}% time {a $mylist} 1000126 microseconds per iteration% time {b $mylist} 1000178 microseconds per iteration

Still ~50% cpu increase though.

Statistics: Posted by strikelight — Wed Jan 28, 2004 8:36 pm

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2004-01-28T20:27:25-04:00

Code:

% proc a {mylist} {set i 0; foreach word $mylist {incr i}}% proc b {mylist} {set i 0; foreach word [set mylist][unset mylist] {incr i}

Your test is not fair, as 'unset' returns an empty STRING, making the list before it become a string that has to be translated back to a list by foreach. (oh, the wonderfull internals of tcl ;P)
Try this instead and you'll see the unset adds very little to the total cpu usage

Code:

proc a it {set i 0; foreach word [split $it] {incr i}; set i}proc b it {set i 0; foreach word [split [set it][unset it]] {incr i}; set i}

Statistics: Posted by user — Wed Jan 28, 2004 8:27 pm

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2004-01-28T20:12:57-04:00

What's the point of unsetting the local variable str? Sure you free up a little bit of memory, but with the command substitution you are adding cpu time... The local variable will be destroyed once the procedure has exited anyways, so for the little time it does spend inside the proc, plus the slight cpu overhead, there's no advantage to unsetting it.
The point is to not have two copies of the entire input stored in memory at any point. In my opinion, saving ~50% memory (for large amounts of data) outweights the disadvantage of the tiny cpu usage added by the unset.

But it probably doesn't matter for what these folks will use it for anyway...and to be perfectly honest I did it to make the boring code have a slightly interesting part for us to talk about right now

Nothing wrong with us having a discussion about it though

Code:

% proc a {mylist} {set i 0; foreach word $mylist {incr i}}% proc b {mylist} {set i 0; foreach word [set mylist][unset mylist] {incr i}}% time {a $mylist} 100026 microseconds per iteration% time {b $mylist} 100081 microseconds per iteration% time {a $mylist} 100036 microseconds per iteration% time {b $mylist} 100091 microseconds per iteration

so while you are correct in stating that you save ~50% in memory,
you are also adding ~200% to ~300% in cpu time

Statistics: Posted by strikelight — Wed Jan 28, 2004 8:12 pm

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2004-01-28T19:55:23-04:00

What's the point of unsetting the local variable str? Sure you free up a little bit of memory, but with the command substitution you are adding cpu time... The local variable will be destroyed once the procedure has exited anyways, so for the little time it does spend inside the proc, plus the slight cpu overhead, there's no advantage to unsetting it.

The point is to not have two copies of the entire input stored in memory at any point. In my opinion, saving ~50% memory (for large amounts of data) outweights the disadvantage of the tiny cpu usage added by the unset.

But it probably doesn't matter for what these folks will use it for anyway...and to be perfectly honest I did it to make the boring code have a slightly interesting part for us to talk about right now

Statistics: Posted by user — Wed Jan 28, 2004 7:55 pm

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2004-01-28T19:42:27-04:00

With which command I can say/split the output in two, three lines when var $a is more than 445 characters?
There's no single command to do that

This is a pretty straight forward word wrapper. the optional third value can be used to split on a different char than space (only one char..sorry ) It returns a list of "lines" that you can do whatever you like with
Code:
proc wordwrap {str {len 70} {splitChr { }}} {set out [set cur {}]; set i 0foreach word [split [set str][unset str] $splitChr] {if {[incr i [string len $word]]>$len} {lappend out [join $cur $splitChr]set cur [list $word]set i [string len $word]} {lappend cur $word}incr i}lappend out [join $cur $splitChr]}
ps: it won't split words even if they're longer than the max length. feature or bug? you decide
pps: it will return a list with one empty element if you feed it an empty string

What's the point of unsetting the local variable str? Sure you free up a little bit of memory, but with the command substitution you are adding cpu time... The local variable will be destroyed once the procedure has exited anyways, so for the little time it does spend inside the proc, plus the slight cpu overhead, there's no advantage to unsetting it.

Statistics: Posted by strikelight — Wed Jan 28, 2004 7:42 pm

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2004-01-28T14:30:13-04:00

With which command I can say/split the output in two, three lines when var $a is more than 445 characters?

There's no single command to do that

This is a pretty straight forward word wrapper. the optional third value can be used to split on a different char than space (only one char..sorry ) It returns a list of "lines" that you can do whatever you like with

Code:

proc wordwrap {str {len 70} {splitChr { }}} {set out [set cur {}]; set i 0foreach word [split [set str][unset str] $splitChr] {if {[incr i [string len $word]]>$len} {lappend out [join $cur $splitChr]set cur [list $word]set i [string len $word]} {lappend cur $word}incr i}lappend out [join $cur $splitChr]}

ps: it won't split words even if they're longer than the max length. feature or bug? you decide
pps: it will return a list with one empty element if you feed it an empty string

Statistics: Posted by user — Wed Jan 28, 2004 2:30 pm

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2004-01-28T09:17:42-04:00

Ok, it works perfect now..... BUT there is a problem

The server allows only ~445 characters per line! Sometimes the output of the above script is more than 445 characters so it stops after this amount of ch.

With which command I can say/split the output in two, three lines when var $a is more than 445 characters?

Statistics: Posted by Jagg — Wed Jan 28, 2004 9:17 am

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2004-01-25T17:35:35-04:00

By converting it to a string with "join" and telling it what to join with, ie. a comma:

Code:

set text [join $yourlist ", "]

Statistics: Posted by strikelight — Sun Jan 25, 2004 5:35 pm

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2004-01-25T13:19:33-04:00

THANKS A LOT!!!!!

I get now a list from all WORD like:

WORD WORD2 WORD3 and so on...

How can I write a comma between these words?

Statistics: Posted by Jagg — Sun Jan 25, 2004 1:19 pm

Re: list specific chapter from a href tag?

2004-01-24T21:34:45-04:00

Try this:

Code:

foreach {word word} [regexp -all -inline {"http://www.url.com/e\?t=([^"]+)"} $html] {  lappend words $word}

Statistics: Posted by user — Sat Jan 24, 2004 9:34 pm