December 05, 2009 Should ^^ (opPow) be left- or right-associative? | |
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Currently in D (r283) opPow is left-associative: 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 right-associative (3^3^3==7e12): - Python, Haskell, Ruby, Perl, Mathematica, Bash. Languages which the power operator is left-associative (3^3^3==19683): - Octave/MATLAB, Excel, BASIC. |

December 05, 2009 Re: Should ^^ (opPow) be left- or right-associative? | |
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Posted in reply to KennyTM~ | ```
KennyTM~:
> But the mathematical convention is a^b^c == a^(b^c).
> Languages which the power operator is right-associative (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 built-in pow, it needs several improvements :-)
Bye,
bearophile
``` |

December 05, 2009 Re: Should ^^ (opPow) be left- or right-associative? | |
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Posted in reply to bearophile | == Quote from bearophile (bearophileHUGS@lycos.com)'s article > This was just the release V.0.1 of the built-in 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 right-associative? | |
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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 right-associative (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 built-in 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/cgi-bin/tct/tip/274.html |

December 05, 2009 Re: Should ^^ (opPow) be left- or right-associative? | |
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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 right-associative (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 built-in 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/cgi-bin/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 right-associative? | |
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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 right-associative (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 built-in 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/cgi-bin/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_non-associative_operations "x^{y^z}=x^{(y^z)}.\, The reason exponentiation is right-associative is that a repeated left-associative 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 right-associative? | |
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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 right-associative (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 built-in 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/cgi-bin/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 right-associative? | |
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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 |