Re: [TCLCORE] Fwd: TIP 672 Implementation Complete - Ready for Sponsorship

[Colin M. <col...@ya...>]

Indeed, this toy implementation doesn't handle that:

    % = sin (12)
    can't read "sin": no such variable

I'm not sure that's serious, but it could be fixed in a C implementation.

Colin.

On 02/11/2025 08:04, Pietro Cerutti wrote:
> How does it handle a space between a mathfunc and its parenthesized 
> argument list?
>
> % expr {sin (12)}
> -0.5365729180004349
>
> -- 
> Pietro Cerutti
> I've pledged to give 10% of income to effective charitiesand invite 
> you to join me.
> https://givingwhatwecan.org
>
> Sent from a small device - please excuse brevity and typos.
>
>
>> On 1 Nov 2025, at 17:50, Colin Macleod via Tcl-Core 
>> <tcl...@li...> wrote:
>>
>> 
>> On 30/10/2025 01:18, Andreas Leitgeb wrote:
>>>    - [= ...] with a modified expr-language using barewords as variable
>>>      names would probably solve many (if not most) of the cases, where
>>>      [expr {...}] really "hurts" for its verbosity.
>>
>> Here is a pure Tcl implementation of that:
>>
>>     proc = args {
>>         set ex [join $args]
>>         set exp [regsub -all
>>     {(::)?[[:alpha:]]([[:alnum:]_]|::)*([^[:alnum:]_(]|$)} $ex {$&}]
>>         uplevel expr $exp
>>     }
>>
>> This just finds all the possible variable names in the expression, 
>> prefixes them with $ and then runs expr on the result.  The regex is 
>> a little complicated because:
>>
>>   * The variable name could include :: at the beginning or in the
>>     middle for namespacing.
>>   * We disallow single colon : within the name because that creates
>>     ambiguity with the ternary operator ?: .
>>   * We also disallow array references because we can't distinguish
>>     them from mathfunc calls.
>>
>> The fact that this can be implemented in pure Tcl shows that it 
>> doesn't require any change to the dodekalogue rules, and so there is 
>> no consequence for subst either.
>>
>> Of course a real implementation should be done in C.  It could then 
>> also be possible to implement the extension Kevin Kenny suggested of 
>> adding `=` as an assignment operator as in C within an expression, 
>> and perhaps even chaining multiple assignments with `,` .
>>
>> I saw the `expr` question is on the agenda for the call on Monday.  I 
>> don't usually join these calls but I would join it for this issue 
>> except that I have an urgent dentist's appointment at that time.  
>> Perhaps I should create a new TIP for this proposal?
>>
>> Colin.
>>
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