Re: DRY vs. KISS
Omer Zak <w1-W6cp89mEpD1mR6Xm/[email protected]> Thu, 12 Nov 2009 20:41:09 +0200
| Newsgroups | gmane.culture.hackers.israel |
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On Thu, 2009-11-12 at 19:24 +0200, Shlomi Fish wrote:
[... an example was snipped ...]
> So the question to you is: do you think DRY and KISS can sometimes contradict
> one another? If so, which one is more important, or that you should just use
> your reason. I should also note that I've been feeling that less expressive
> languages sometimes result in being unable to avoid duplicate code or
> undesirable "patterns" in the code (in accordance to DRY). Possibly the only
> family of languages that completely avoids duplicate code is Lisp.
I think that more important than DRY, KISS or whatever is the principle
of not overloading the memory of whomever is going to read the software.
You overload his memory if he has to look up elsewhere for definitions
of variables, functions, closures or whatever constructs you are using.
According to this criteria, LISP can be very bad.
If you define another function in order to avoid code repetition at 3
places in your project, then whomever is reading the code needs to look
up the new function definition. If it's the only function in the
statement - OK. But if the statement already invokes 7 functions to
compute values, return a function pointer to be invoked, and the address
of the variable to receive the result, then adding 8th function would
already overflow the reader's short term memory.
And sometimes when you need to modify all copies of an expression in
your project, egrep can do good enough work - so no need to make them a
function to enable code modification at one place. In a way it would be
"virtual DRY" - the entity which you don't repeat is the egrep pattern.
Those are vague ideas. I hope that someone would continue the
conversation and can distill those ideas and find the hidden principle -
it surely would be a gem!
--- Omer
--
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<p>On Thu, 2009-11-12 at 19:24 +0200, Shlomi Fish wrote:<br>
[... an example was snipped ...]<br>
> So the question to you is: do you think DRY and KISS can sometimes contradict <br>
> one another? If so, which one is more important, or that you should just use <br>
> your reason. I should also note that I've been feeling that less expressive <br>
> languages sometimes result in being unable to avoid duplicate code or <br>
> undesirable "patterns" in the code (in accordance to DRY). Possibly the only <br>
> family of languages that completely avoids duplicate code is Lisp.<br>
<br>
I think that more important than DRY, KISS or whatever is the principle<br>
of not overloading the memory of whomever is going to read the software.<br>
<br>
You overload his memory if he has to look up elsewhere for definitions<br>
of variables, functions, closures or whatever constructs you are using.<br>
According to this criteria, LISP can be very bad.<br>
<br>
If you define another function in order to avoid code repetition at 3<br>
places in your project, then whomever is reading the code needs to look<br>
up the new function definition. If it's the only function in the<br>
statement - OK. But if the statement already invokes 7 functions to<br>
compute values, return a function pointer to be invoked, and the address<br>
of the variable to receive the result, then adding 8th function would<br>
already overflow the reader's short term memory.<br>
<br>
And sometimes when you need to modify all copies of an expression in<br>
your project, egrep can do good enough work - so no need to make them a<br>
function to enable code modification at one place. In a way it would be<br>
"virtual DRY" - the entity which you don't repeat is the egrep pattern.<br>
<br>
Those are vague ideas. I hope that someone would continue the<br>
conversation and can distill those ideas and find the hidden principle -<br>
it surely would be a gem!<br>
--- Omer<br>
-- <br>
Eli Marmor's Law: netiquette forbids people from replying "I agree with<br>
you" to messages in mailing lists, skewing discussions in favor of the<br>
troublemaker type of dissenters.<br>
My own blog is at <a href="http://www.zak.co.il/tddpirate/">http://www.zak.<wbr>co.il/tddpirate/</a><br>
<br>
My opinions, as expressed in this E-mail message, are mine alone.<br>
They do not represent the official policy of any organization with which<br>
I may be affiliated in any way.<br>
WARNING TO SPAMMERS: at <a href="http://www.zak.co.il/spamwarning.html">http://www.zak.<wbr>co.il/spamwarnin<wbr>g.html</a><br>
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