Re: [TCLCORE] Demand of sponsorship : TIP "Mathematical expression substitution"

[Brian G. <bri...@ea...>]

On Mar 3, 2026, at 20:29, EricT <tw...@gm...> wrote:

Ah yes. I see it says it is done as a pre-pass. And I now also know why the spaces and tabs on the next line are also removed.

IMHO, however, I think this was a mistake, since it does tend to throw off reported line numbers in error messages, unless one's text editor understands this. I have many and not a one understands this distinction.

That view is understandable. However, in Tcl, everything is a string first and foremost. A string is only a program when it is evaluated.
Otherwise, it's just data. This is what makes things like CriTcl easy and possible.

This concept is hard to appreciate at first.

-Brian


-eric


On Tue, Mar 3, 2026 at 7:03 PM Brian Griffin <bri...@ea...<mailto:bri...@ea...>> wrote:
Correct, because "\" is a duodecalogue<https://www.tcl-lang.org/man/tcl8.6/TclCmd/Tcl.htm%23M16> defined substitution.
Substitutions are done before the statements are parsed.

-Brian

On Mar 3, 2026, at 12:53, EricT <tw...@gm...<mailto:tw...@gm...>> wrote:

Hi Florent:

Very nice implementation.

With respect to <newline> being a command separator, this is the natural syntax of Tcl.   Tcl allows for \<newline> as a continuation. That is why in my own implementation I simply map <newline> to ; (semi-colon) in a pre-pass. If I recall, in Tcl, the \<newline> is apparently removed,

Not just apparently, but explicitly spelled out. :)

since with this:


proc foo123 args {
     set var \
     "some string"
 }

% info body foo123

     set var  "some string"

I believe this also affects line numbering in error messages.

regards,

Eric


On Tue, Mar 3, 2026 at 1:54 AM Florent Merlet <flo...@gm...<mailto:flo...@gm...>> wrote:

Hi Eric,

1. you can write (1, 2, 3) or list(1, 2, 3) if you wish to : The implementation includes « list » into mathfunc.

2. Actually, newline are not command separators. I don't think I will make it like this, because I prefer to split a very long expression on many lines for readibility (espacially for matrix). For example :

proc TensorialProduct {V U} {
    lassign $V x y z
    lassign $U u v w

    return [( a11 = $x*$u; a12 = $x*$v;  a13 = $x*$w;
              a21 = $y*$u; a22 = $y*$v;  a23 = $y*$w;
              a31 = $z*$u; a32 = $z*$v;  a33 = $z*$w;
              (($a11, $a12, $a13),
               ($a21, $a22, $a23),
               ($a31, $a32, $a33)))]
}

3. This is an error :

% set x [(x=3;;$x+1)]
missing operand at _@_ in expression "(x=3;_@_;$x+1)]"

But this is valid :

set L [(
    x = 2;
    y = $x*3;

    ($x, $y, $x*$y)
       )]
puts L:$L
L:{2 6 12}

4. You can write :

set A [( x = 3; # set x
         # comment
         y = 4; # set y
         # result
         $y+$x)]

Comments must begin after a semi-colon or a newline, but must finish with a newline.

This works also :

puts [(
       x = 2 ; # simple assignment of x
       y = $x*3 ;
       list($x, $y, $x*$y) # comment without ";" is OK at the end
       )]

This doesn't :

puts [(
       x = 2 # Comment without ";" before is NOK inside
       y = $x*3 ;
       list($x, $y, $x*$y) # comment without ";" is OK at the end.
       )]

(bug to be investigated : TclStackFree: incorrect freePtr (0xa000262d0 != 0xa00026330). Call out of sequence?
Illegal instruction)

As ";" is map as a binary operator, it's waiting for an operand on its right. To turn around, you must give it something, beyond anything which is valid in expr, like for instance :

% set x [(
   x=3;
   "A comment
   as a words
   in quotes";
   1.0e-10;# any valid number is possible
   {  A comment
       as bracedword
   };
   [   # A comment as
       # word script
      ];
   $x+1 )]


5. This is working (TIP 282 made assign it right associative) :

set M [( m12 = m21 = m13 = m31 = m23 = m32 = 0;
         m11 = m22 = m33 = 1;
         (($m11, $m12, $m13),
          ($m21, $m22, $m23),
          ($m31, $m32, $m33)) )]

And returns : {{1 0 0} {0 1 0} {0 0 1}}

6. Yes it a new substitution rule only. But expr, or any alias of it, is there as a command. So, you can write

expr {m12 = m21 = m13 = m31 = m23 = m32 = 0;  m11 = m22 = m33 = 1}

Moreover, as the TIP282 are in `expr` , you can use this feature in : `while`, `for`, `if`
You may refer to the Eratosthenes Sieve example, the one with TIP282 integration, given in the updated TIP<https://github.com/florentis/tcl-ExprShorthand/blob/main/TIP-shorthand.md>

proc sieve {n} {
    set L [lseq $n]
    for {set i 2} {(j = $i) < $n} {incr i} {
       while {(k = $i*$j) < $n} {
          lset L $k {}
          incr j
       }
    }
    return [lsearch -all -not -exact $L {}]
}


7. bareword variable arithmetic :

For the moment bareword as variable is only legal on the left side of the assignement operator.
That follows this well known pattern of Tcl : set x $y <=> x = $y

Will this TIP allows it ? Well, myself, I don't know how to do it yet. So It won't be allowed by myself yet... If someone has an idea...

Personnally, my priority would go to introduce list assignement capabilities :

set tM [((row1,row2,row3)=$M;
          (a11,a12,a13)=$row1;
          (a21,a22,a23)=$row2;
          (a31,a32,a33)=$row3;
          # transpose the matrix :
          (($a11,$a21,$a31),
           ($a12,$a22,$a32),
           ($a13,$a23,$a33)))]

# could be made equivalent to :

set tM [lassign $M row1 row2 row3
        lassign $row1 a11 a12 a13
        lassign $row2 a21 a22 a23
        lassign $row3 a31 a32 a33
        # transpose the matrix
        list [list $a11 $a21 $a31] \
             [list $a12 $a22 $a32] \
             [list $a13 $a23 $a33]]

 Thanks a lot for your interest. I hope you found in my reply all the answers to your questions.

I'm very admirative of your work and get many ideas from it.
You helped me a lot when you explained me the basics of Tcl pointer arithmetic. Without your explanations, I would have never enter in a big code like Tcl.

I'm still waiting to hear people of the core team, but whatever will be their replys, I want to thank you for everything.

Cordially,

Florent

Le 02/03/2026 à 23:02, EricT a écrit :

Hi Florent:

I haven't had a chance to study your implementation; however, with the addition of the = operator, you are very close to the project I implemented as a fork of Colin's original pure tcl "=" command.

Here are some items that I implemented that I think you likely could add easily, if you haven't already done so.

1. Sometimes it's better to include a hint as to what is occuring. Your list operation,

    (1, 2, 3)

might actually be better written as,

     list(1, 2, 3)

And this is easily implemented as a mathfunc:

    proc tcl::mathfunc::list {args} {
        return [::list {*}$args]
    }



2. Treat a \n (newline) the same as ; (semi-colon) for command separators. Then you could easily have,

    set L [( x = 2
             y = $x*3
             list($x , $y, $x*$y)
          )]

3. Allow for null statements (which get ignored) so ;; or multiple newlines would work as well, so that could also be written:

    set L [(
             x = 2
             y = $x*3

             list($x , $y, $x*$y)
          )]

4. For compatibility with expr, allow on-the-line comments (if not already implemented)

    set L [(
             x = 2               ;# simple assignment of x
             y = $x*3
             list($x , $y, $x*$y) # comment without the ; needed
          )]

Allowing a null statement to be ignored (comment 3. above) is what would allow for both the use of ;# or # alone to work.


5. Allow for right associativity and chaining of the = (assignment) operator. This would allow for,

    set L [( a = b = c = 0 )]


6. I don't see a way that your implementation allows for an expression that is a complete command. That is, you appear to require it be an argument only. Is there some way to be able to write,

    [( a = b = c = 0 )]


alone on a line as just a single command?

7. What will it take to support bare variable arithmetic?

    set L [(
             x = 2
             y = x*3
             list(x , y, x*y)
          )]


Thanks for adding to the "neo-expr" project. Here's a reference to my fork of Colin's = command.

https://github.com/rocketship88/colin-parser



-Eric



On Mon, Mar 2, 2026 at 6:32 AM Florent Merlet <flo...@gm...<mailto:flo...@gm...>> wrote:

Dear Tcl Core team,

Finally, I split the proposal in 4 repositories. They can be found at https://github.com/florentis<https://github.com/florentis/tcl-ExprShorthand/blob/main/TIP-shorthand.md>

  *   The forth<https://github.com/florentis/tcl-ExprShorthand-index-list-TIP282> is for TIP 282 integration : It would allow us to write :

set L [( x=2; y =$x*3; ($x , $y, $x*$y) )]
# set x to 2, set y to 6, set L to {2 6 12}


Cordially,

Florent

Le 02/03/2026 à 01:32, Florent Merlet a écrit :

Dear Tcl Core team,

Following my last developpements on the subject concerning a Tcl expression shorthand, I have produced a TIP.

The text of this TIP<https://github.com/florentis/tcl-ExprShorthand/blob/main/TIP-shorthand.md> can be found at this url : https://github.com/florentis/tcl-ExprShorthand/blob/main/TIP-shorthand.md

I splitted the proposal in 3 repositories :

  *   The first<https://github.com/florentis/tcl-ExprShorthand> is for the basic expression shorthand. It would allow us to write :

set A [( ... )]

  *   The second<https://github.com/florentis/tcl-ExprShorthand-index> add the shorthand dedicated to array index. It would allow us to write :

set B((...))  value

  *   The third<https://github.com/florentis/tcl-ExprShorthand-index-list> add a native list handling in expression. It would allow us to write :

set M((1+1)) [(  (1,0,0) , (0,1,0) , (0,0,1)  )]

Each of those repositories contains the modified c-files from the Tcl9.1a trunk and the tclsh.exe that results from the compilation on my machine (Win 10 / cygwin + gcc).

May you have a look and give me feedback ?

Would someone of the core team be ready to sponsor it ?

Cheers


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