Thread overview  


December 05, 2009 Should ^^ (opPow) be left or rightassociative?  

 
Currently in D (r283) opPow is leftassociative: import std.stdio; void main() { // prints 19683 instead of 7625597484987: writeln(3.0 ^^ 3.0 ^^ 3.0); } But the mathematical convention is a^b^c == a^(b^c). Languages which the power operator is rightassociative (3^3^3==7e12):  Python, Haskell, Ruby, Perl, Mathematica, Bash. Languages which the power operator is leftassociative (3^3^3==19683):  Octave/MATLAB, Excel, BASIC. 
December 05, 2009 Re: Should ^^ (opPow) be left or rightassociative?  

 
Posted in reply to KennyTM~  KennyTM~:
> But the mathematical convention is a^b^c == a^(b^c).
> Languages which the power operator is rightassociative (3^3^3==7e12):
>  Python, Haskell, Ruby, Perl, Mathematica, Bash.
Doing things as in mathematical convention, Mathematica and Python sounds better. This was just the release V.0.1 of the builtin pow, it needs several improvements :)
Bye,
bearophile

December 05, 2009 Re: Should ^^ (opPow) be left or rightassociative?  

 
Posted in reply to bearophile  == Quote from bearophile (bearophileHUGS@lycos.com)'s article > This was just the release V.0.1 of the builtin pow, it needs several improvements :) See also bug 3577. ^^ should have higher precedence than * and / to be consistent w/ mathematical convention. http://d.puremagic.com/issues/show_bug.cgi?id=3577 
December 05, 2009 Re: Should ^^ (opPow) be left or rightassociative?  

 
Posted in reply to bearophile  bearophile wrote: > KennyTM~: >> But the mathematical convention is a^b^c == a^(b^c). >> Languages which the power operator is rightassociative (3^3^3==7e12): >>  Python, Haskell, Ruby, Perl, Mathematica, Bash. > > Doing things as in mathematical convention, Mathematica and Python sounds better. > This was just the release V.0.1 of the builtin pow, it needs several improvements :) > > Bye, > bearophile Fortran too. Here's a link from the TCL language, with a nice explanation of the rationale for choosing right associativity. http://www.tcl.tk/cgibin/tct/tip/274.html 
December 05, 2009 Re: Should ^^ (opPow) be left or rightassociative?  

 
Posted in reply to Don  "Don" <nospam@nospam.com> wrote in message news:hfei3u$kvk$1@digitalmars.com... > bearophile wrote: >> KennyTM~: >>> But the mathematical convention is a^b^c == a^(b^c). >>> Languages which the power operator is rightassociative (3^3^3==7e12): >>>  Python, Haskell, Ruby, Perl, Mathematica, Bash. >> >> Doing things as in mathematical convention, Mathematica and Python sounds >> better. >> This was just the release V.0.1 of the builtin pow, it needs several >> improvements :) >> >> Bye, >> bearophile > > Fortran too. > Here's a link from the TCL language, with a nice explanation of the > rationale for choosing right associativity. > > http://www.tcl.tk/cgibin/tct/tip/274.html Quick summary for those who don't want to dig through that whole page: (a ^^ b) ^^ c == a ^^ (b * c) < For all real values of a, b, and c So kinda useless, but... a ^^ (b ^^ c) == .... a ^^ (b ^^ c) So more useful. 
December 06, 2009 Re: Should ^^ (opPow) be left or rightassociative?  

 
Posted in reply to Don  Don wrote: > bearophile wrote: >> KennyTM~: >>> But the mathematical convention is a^b^c == a^(b^c). >>> Languages which the power operator is rightassociative (3^3^3==7e12): >>>  Python, Haskell, Ruby, Perl, Mathematica, Bash. >> >> Doing things as in mathematical convention, Mathematica and Python sounds better. >> This was just the release V.0.1 of the builtin pow, it needs several improvements :) >> >> Bye, >> bearophile > > Fortran too. > Here's a link from the TCL language, with a nice explanation of the rationale for choosing right associativity. > > http://www.tcl.tk/cgibin/tct/tip/274.html Don I thought you were the one who created the patch http://d.puremagic.com/issues/show_bug.cgi?id=3481 What was your reason for the choice of left associativity? To cite wikipedia: http://en.wikipedia.org/wiki/Associativity#Notation_for_nonassociative_operations "x^{y^z}=x^{(y^z)}.\, The reason exponentiation is rightassociative is that a repeated leftassociative exponentiation operation would be less useful. Multiple appearances could (and would) be rewritten with multiplication: (x^y)^z=x^{(yz)}.\," 
December 06, 2009 Re: Should ^^ (opPow) be left or rightassociative?  

 
Posted in reply to Tim Matthews  Tim Matthews wrote:
> Don wrote:
>> bearophile wrote:
>>> KennyTM~:
>>>> But the mathematical convention is a^b^c == a^(b^c).
>>>> Languages which the power operator is rightassociative (3^3^3==7e12):
>>>>  Python, Haskell, Ruby, Perl, Mathematica, Bash.
>>>
>>> Doing things as in mathematical convention, Mathematica and Python sounds better.
>>> This was just the release V.0.1 of the builtin pow, it needs several improvements :)
>>>
>>> Bye,
>>> bearophile
>>
>> Fortran too.
>> Here's a link from the TCL language, with a nice explanation of the rationale for choosing right associativity.
>>
>> http://www.tcl.tk/cgibin/tct/tip/274.html
>
> Don I thought you were the one who created the patch http://d.puremagic.com/issues/show_bug.cgi?id=3481
>
> What was your reason for the choice of left associativity?
It was a quick patch to determine if Walter could be swayed to include it, if he didn't need to implement it. I didn't get any positive feedback about it until it was put into svn.

December 06, 2009 Re: Should ^^ (opPow) be left or rightassociative?  

 
Posted in reply to Don  Don wrote: > > It was a quick patch to determine if Walter could be swayed to include it, if he didn't need to implement it. I didn't get any positive feedback about it until it was put into svn. Ok thanks a lot for getting a truly important operator implemented. I tried to give my feedback in the ng post back in august http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D&article_id=95596 
Copyright © 19992016 by Digital Mars ®, All Rights Reserved