Re: [TCLCORE] Some expr sillyness

[David S. <Dav...@sy...>]

I agree. I have been using and shipping product using tcl an tk since the late 90's. Tcl's value has been simplicity and regularity. If I want complexity and obfuscation I can always use perl. A lot of the ideas I see being proposed for tcl (such as this) seem like either medalling or a desire for a completely new language. Please do not forget what makes tcl special and do not turn it into a Frankenstein of a language. 

Regards
David
--------------------------
David W. Smith
Synopsys Scientist
W: 503.547.6467
M: 650.861.9814

----- Original Message -----
From: Kristoffer Lawson [mailto:se...@sc...]
Sent: Sunday, May 22, 2011 02:48 AM
To: Donal K. Fellows <don...@ma...>
Cc: tcl...@li... <tcl...@li...>
Subject: Re: [TCLCORE] Some expr sillyness


On 22 May 2011, at 10:59, Donal K. Fellows wrote:

> Expressions are already a little language of their own. They have been
> since at least as far back as Tcl's “changes” file goes (early 1990 is
> the first date[*], but that's not the beginning and [expr] already had
> operators then; Tcl 3.0 is the _latest_ that expressions could have been
> introduced). As such, we can put things into here (e.g., to deal with
> lists and dicts) without the same amount of difficulty. I also have
> tremendous sympathy for wanting to find a shorter outer syntax for
> [expr] itself; producing a list of computed values is _very_ verbose.

Yes, I'm aware of this. However currently, while [expr] is a language of its own from the point of view of the actual expressions (ie. bringing infix operators), everything else still follows Tcl's normal rules. Variable and command substitution behave almost exactly as they would outside [expr]. Changing that is a very dangerous path to be taking as you're going beyond the idea of having a small sub-language for doing math operations to one which is effectively a Turing-complete language of its own. Even if you don't bring in all the syntax people have been talking about here, you are still bringing a whole new set of sub-language abilities which look and act completely differently from outside it.

This will add a huge level of complexity to Tcl, will force people studying the language to effectively learn two languages, it will create questions as to why one syntax works in one place and not another (further aggravated by any 9.0 syntax to do expressions) and will increase the difficulty of understanding code, due to its modal nature.

While I do often wish for something shorter for expressions than the full [expr {...}] (and math ops as commands has greatly reduced that pain), the above is unnecessary sugar and will not make Tcl adoption for newcomers any easier at all. For anyone who has a big need for something like this, just let them build or use an extension.

-- 
Kristoffer Lawson, Co-Founder, Scred // http://www.scred.com/
http://travellingsalesman.mobi - 10000km & The world's most arctic startups


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