I found a little more on this at:

http://www.macnauchtan.com/pub/precedence.html

It says that many softwares don't comply with 'chalkboard' math rules.

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Microsoft Excel 4 CAUT[ion] Index
A B C
1 2.0 2 numeric entry
2 = - A1^2 4 return is positive
3 = - A1^2 / 4 1 return is positive
4 = - + A1^2 4 return is +4 without error message

Microsoft acknowledges the disconnect with chalkboard algebra for all
versions of Excel calling it an "unexpected positive value" but argues that
the result is correct because of their order of operations. The suggested
workaround is to use prophylactic parentheses.


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Microsoft Excel 2001 CAUT[ion] Index
A B C
1 2.0 2 numeric entry
2 =-A1^2 4 return is positive
3 =2 2
4 =5 5
5 = - A3^2 / (-A3^2-A4^2) - A4^2 / (-A3^2-A4^2) 1 return is positive
6 =(- A4^2 - A3^2) / (- A3^2 - A4^2) -1 return is negative

The behavior is the same as Excel 4 but note that macros and user defined
functions written in VBA work the opposite way. A user defined function
avoids the unary minus interpretation just as, say, = - SQRT(A1) would.

In the help documentation for Excel 2001 one finds, for the error function
add-in, this definition:



But what is that -t2? The kernel of the integral is exp(-t^2) and the reader
is invited to make a plot of that. You will create a curve,which has value 1
at t = 0 and increases exponentially at each side. It's a far cry from the
infamous Bell Curve that is the correct Gaussian form for the error
function. One needs to call out exp(0-t^2) or exp (-(t^2)) in Excel.