Hi,
lorieul schrieb:
Hello to all,
I have found a fancy behavior of Calc but I cannot decide whether it is
a bug or a "feature". Hence I was looking for your advice before posting
a bug report (if required).
That is good. It is
https://bugs.documentfoundation.org/show_bug.cgi?id=37271
1. Open LO Calc
2. In A1 enter formula "=1-2^2" and press enter key
The result shown is -3 which is ok since
1-2² = 1-(2²) = 1-4 = -3
3. In A2 enter formula "=-2^2" and press enter key
I would expect this to be treated as -2² = -(2²) = -4
But Calc considers it as (-2)² = +4
Quite obviously, a work around is to define the formula as
"=-(2^2)" which indeed returns -4
I've checked the wiki page dedicated to operators [1] but it does not
give much information on operator precedence.
From my standpoint, both examples show an inconsistent behavior of Calc.
For me, either we should have both 1-2^2 = 1+4 = 5 and -2^2 = +4
Or we should have both 1-2^2 = 1-4 = -3 and -2^2 = -4
A minus can be a binary operator subtraction or a unary operator sign.
In "=1-2^2" there is a operand left and right of the minus, so it is a
binary operator. This means calculate its operands and then subtract.
In "=-2^2" there is no operand left. Therefore the minus can only be a
unary operator, which means, it is a sign of the number. So Calc takes
the number -2 and puts it to the power 2.
However, perhaps some of you have a different view point on the matter ?
In other words, is that a bug or is it perfectly normal ?
It is no bug, but a bad UI, because pupils are thought, that -2² is -4.
One solution to fit common understanding to the formal term
interpretation you can see in Gnumeric. It simple does not allow it.
When the user enters =-2^2 it automatically adds brackets, so that it
becomes (-2)^2 and the users knows the meaning unambiguous.
To force a result of -4 you need to tell Calc, that the minus is a
binary operator. The formula "=0-2^2" would do that.
Of course changing such behavior will cause a hell lot of trouble in
existing documents… but perhaps the operator precedence should be
explicitly specified on the wiki ?
The precedence is defined in ODF
http://docs.oasis-open.org/office/v1.2/os/OpenDocument-v1.2-os-part2.html#Operators
Kind regards
Regina
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