List elements having a leading "#" character are handled specially if they are the first element of
a list:

% set lst1 [list a]
a
% set lst2 [list #b #c]
{#b} #c
%


With Tcl8.6.11, joining these two lists using [concat] squashes one level of grouping (as
documented) and gives the result (as I expected):

% concat $lst1 $lst2
a #b #c
%

However, with Tcl8.6.12 (and Tcl8.7a5) I get:

% concat $lst1 $lst2
a {#b} #c
%


Which of these two behaviours is correct, and why?

Thanks in advance,
Erik Leunissen
--
elns@ nl | Merge the left part of these two lines into one,
xs4all. | respecting a character's position in a line.

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* Erik Leunissen <[email protected]d>
| List elements having a leading "#" character are handled specially if
| they are the first element of a list:

| % set lst1 [list a]
| a
| % set lst2 [list #b #c]
| {#b} #c
| %


| With Tcl8.6.11, joining these two lists using [concat] squashes one
| level of grouping (as documented) and gives the result (as I
| expected):

| % concat $lst1 $lst2
| a #b #c
| %

| However, with Tcl8.6.12 (and Tcl8.7a5) I get:

| % concat $lst1 $lst2
| a {#b} #c
| %


| Which of these two behaviours is correct, and why?

Both are. What you see as the result of 'concat' is the string
representation of the list, and obviously 8.6.12 decides to add more
quoting for some reason.

If you inspect the list, you get identical contents in 8.6.11 and 8.6.12:

% info patchlevel
8.6.11
% set lst1 [list a]
a
% set lst2 [list #b #c]
{#b} #c
% set lst3 [concat $lst1 $lst2]
a #b #c
% foreach elt $lst3 { puts $elt }
a
#b
#c

% info patchlevel
8.6.12
% set lst1 [list a]
a
% set lst2 [list #b #c]
{#b} #c
% set lst3 [concat $lst1 $lst2]
a {#b} #c
% foreach elt $lst3 { puts $elt }
a
#b
#c

HTH
R'

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On 06/11/2021 13:57, Ralf Fassel wrote:

Both are. What you see as the result of 'concat' is the string representation of the list, and obviously 8.6.12 decides to add more
quoting for some reason.

That's all well, but consider the following test
(the test is taken from a Tk package where it
is important to verify correct colour selection) :


package require tcltest
tcltest::test exercise {check colour selection} -body {
set result [list black black black]
# do other stuff
concat $result [list #00ff00 #00ff00 #00ff00]
} -result [list black black black #00ff00 #00ff00 #00ff00] tcltest::cleanupTests


When this test is exercised by a user running Tcl < 8.6.12 the test passes. Suppose this test comes
from a stable package, that doesn't receive frequent updates anymore. Now users are going to install
Tcl8.6.12, run the test and it suddenly fails.

Something is very awkward here (a missed *** POTENTIAL INCOMPATIBILITY *** ?), or would you say that
the test was incorrect all along?

Erik
--

If you inspect the list, you get identical contents in 8.6.11 and 8.6.12:

% info patchlevel
8.6.11
% set lst1 [list a]
a
% set lst2 [list #b #c]
{#b} #c
% set lst3 [concat $lst1 $lst2]
a #b #c
% foreach elt $lst3 { puts $elt }
a
#b
#c

% info patchlevel
8.6.12
% set lst1 [list a]
a
% set lst2 [list #b #c]
{#b} #c
% set lst3 [concat $lst1 $lst2]
a {#b} #c
% foreach elt $lst3 { puts $elt }
a
#b
#c

HTH
R'

--
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On 06/11/2021 16:04, Erik Leunissen wrote:

..
    concat $result [list #00ff00 #00ff00 #00ff00]
...

I forgot to mention that [concat] was chosen on purpose for this test.
It was meant to remove one level of grouping.

Erik.
--
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Am 06.11.2021 um 13:36 schrieb Erik Leunissen:

List elements having a leading "#" character are handled specially if
they are the first element of a list:

% set lst1 [list a]
a
% set lst2 [list #b #c]
{#b} #c
%

With Tcl8.6.11, joining these two lists using [concat] squashes one
level of grouping (as documented) and gives the result (as I expected):

% concat $lst1 $lst2
a #b #c
%

However, with Tcl8.6.12 (and Tcl8.7a5) I get:

% concat $lst1 $lst2
a {#b} #c
%

Which of these two behaviours is correct, and why?

Thanks in advance,
Erik Leunissen

Dear Eric,
afaik, concat has special features to build TCL commands.
I suppose, that is the reason, why the "#" is handled in a special way.

Perhaps, this special treatments got broken in TCL 8.6.12, or it is only
the string representation which is wrong.
I would prefer to open a bug on TCL to get more comments.

Take care,
Harald

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See ticket https://core.tcl-lang.org/tcl/info/26649439c7

You are correct this would have been better marked with a POTENTIAL INCOMPATIBILITY.

[concat] is a string operation that follows a prescribed algorithm of
joining strings together with single intervening spaces after trimming
extra whitespace away. Honestly, it's very weird. It does not reliably produce canonical lists and never has.

% concat {foo bar } " x y\tz\ngrok"
foo bar x y z
grok
% concat foo \{
foo {

Until 8.6.12, the implementation of [concat] contained some
optimizations when arguments were internally of the list type, but those optimizations were producing different results from a non-optimized
approach. Since Tcl commands must treat all equal values (viewed as
strings) the same, independent of internal representation and type, this violation was fixed.

Note that your example use of [concat] still produces a list, a list
containing all the same elements. Only the element formatting has
changed.

To get the same result you are accustomed to...

% concat $lst1 $lst2
a {#b} #c
% list {*}$lst1 {*}$lst2
a #b #c


On 11/6/21 8:36 AM, Erik Leunissen wrote:

List elements having a leading "#" character are handled specially if
they are the first element of a list:

% set lst1 [list a]
a
% set lst2 [list #b #c]
{#b} #c
%

With Tcl8.6.11, joining these two lists using [concat] squashes one
level of grouping (as documented) and gives the result (as I expected):

% concat $lst1 $lst2
a #b #c
%

However, with Tcl8.6.12 (and Tcl8.7a5) I get:

% concat $lst1 $lst2
a {#b} #c
%

Which of these two behaviours is correct, and why?

Thanks in advance,
Erik Leunissen

--
| Don Porter Applied and Computational Mathematics Division |
| [email protected] Information Technology Laboratory |
| http://math.nist.gov/~DPorter/ NIST | |______________________________________________________________________|

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On 07/11/2021 14:47, Don Porter wrote:

See ticket https://core.tcl-lang.org/tcl/info/26649439c7

You are correct this would have been better marked with a POTENTIAL INCOMPATIBILITY.

Thanks very much Don, for this entirely complete explanation:

[concat] is a string operation that follows a prescribed algorithm of
... etc

And for this recommended remedy (which is exactly what I already had in place as a solution for this
case):

To get the same result you are accustomed to...

% concat $lst1 $lst2
a {#b} #c
% list {*}$lst1 {*}$lst2
a #b #c

It left absolutely not a single loose end for my understanding.

Erik.
--

On 11/6/21 8:36 AM, Erik Leunissen wrote:

List elements having a leading "#" character are handled specially if they are the first element
of a list:

% set lst1 [list a]
a
% set lst2 [list #b #c]
{#b} #c
%


With Tcl8.6.11, joining these two lists using [concat] squashes one level of grouping (as
documented) and gives the result (as I expected):

% concat $lst1 $lst2
a #b #c
%

However, with Tcl8.6.12 (and Tcl8.7a5) I get:

% concat $lst1 $lst2
a {#b} #c
%


Which of these two behaviours is correct, and why?

Thanks in advance,
Erik Leunissen

--
elns@ nl | Merge the left part of these two lines into one,
xs4all. | respecting a character's position in a line.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)