On 30/03/16 13:52, Alex McMurchy wrote:
Unless I'm misremembering my maths -2² would be +4 and -(2²) would be -4
So in my mind no bug.
Just a matter of convention. Unfortunately where there's one, there's
another.......
It seems that perl, python and php differ. Perl and python I've tried
and it's so, php's manual puts exponentiation at higher precedence than
unary - (http://php.net/manual/en/language.operators.precedence.php)
although the ** operator is new in php 5.6 so I can't check offhand.
eg
mike@spock> python
Python 2.7.6 (default, Jun 22 2015, 17:58:13)
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> print -3 ** 2
-9
Excel is documented as Calc's order, ie the opposite.
Javascript seems to agree with Excel.
(https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Operators/Operator_Precedence)
Fortran (remember that?) puts - below **
(https://www.fortran.com/F77_std/rjcnf0001-sh-6.html)
that page says explicitly
"For example, in the expression
- A ** 2
the exponentiation operator (**) has precedence over the negation
operator (-) .... The interpretation of the above expression is the same
as the interpretation of the expression
- (A ** 2)
"
Oddly, I can't find any strictly /mathematical/ guideline! Anyone have
the maths students' guide to operator precedence?
It looks as though opinion is divided.
I'd suggest always using brackets to be sure and clear. In any case, it
really needs documenting for Calc.
--
Mike Scott (unet2 <at> [deletethis] scottsonline.org.uk)
Harlow Essex England
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