Re: math operators
On Sat, 20 Sep 2003 16:50:39 +0200, Juergen Luethje <j.lue at gmx.de>
wrote:
>And how about the power operator? What is the result of
> 2^3^2 ?
>
>Mathematically, evaluation is right to left for the power operator! So
> 2^3^2 =3D 2^(3^2) =3D 2^9 =3D 512.
>
>But there seems to be a kind of "industry standard", that says that such
>expressions should be calculated from left to right. That means:
> 2^3^2 =3D (2^3)^2 =3D 8^2 =3D 64
When I wrote the expression evaluator for my report generator, I snuck
^ in and found EXACTLY that example! After thinking about it a while,
I made the operator non-associative so if you key that expression it
complains "ambiguous: add parenthesis".
>>> BITWISE OPERATORs
>>> compare() become =3D=3D
>>> and_bits() become &&
>>> or_bits() become ||
>>>
>>> or at least see them used as operators. Such as:
>>> if (int1 and_bits int2) then
>>> if (int2 or_bits int2) then
>>> end if
>>> end if
>>> But that wouldn't be backwards compatible. :(
>>
>> again, yes!
>
>No, please!
>I'm happy that Euphoria code is very good readable ATM.
>I would not be happy to see anything that makes it less readable.
As an aside, I based my expression evaluator on a paper by Thomas
Niemann (http://epaperpress.com/oper/index.html) which, as the author
admits, has some unusual effects: All of the following evaluate to 25:
power 5 2
power() 5 2
power(5) 2
power(5,2)
5 power 2
5 power() 2
5 power(2)
5 2 power()
^ 5 2
5^2
5 2 ^
If anyone is interested, I'll clean it up and post it. Maybe someone
with a fresh perspective can fix that for me.
I also support and_bits and or_bits, which can also be written infix.
Elliot wrote:
>(For those who thought ^ was power, it really is bitwise XOR.)
Yes, you're probably right. I think I'll remove the ^ operator.
Regards,
Pete
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