On Thu, Nov 08, 2007 at 09:30:06AM +0100, Jonathan Sauer wrote:
> I hope this is the right place for this.
>
> Macro \int_div_truncate_raw:nn is defined in file l3int as:
>
> \def_new:Npn \int_div_truncate_raw:nn #1#2 {
> \int_eval:n{ (2*#1  #2) / (2* #2) }
> }
>
> If #1 is zero and #2 is two, this macro does not expand to zero,
> as one would expect (0 / 2 = 0), but to 1 (since eTeX rounds
> negative numbers by negating them, rounding the positive number
> and negating the result. See function "quotient" in etex.ch).
This eTeXrounding does not make life easier. :((
> Also, if #2 is an expression (i.e. 1+1), the calculation is not
> performed correctly, since #2 (and #1) is not surrounded by ( and ).
> (I am not sure if this can happen, or if the parameters are always
> evaluated beforehand)
>
> In my code, I use (to divide #1 by #2):
>
> \numexpr((((#1)+((#2)/2))/(#2))1)\relax
With less parentheses:
\numexpr (#1+(#2)/2)/(#2)1\relax
> This seems to work better.
No: 2/2 = 2
Also both solutions have the disadvantage, that intermediate
results may cause an arithmetic overflow. As result the
accepted number range is limited unnecessarily.
Therefore I have choosen a more complicate route in
package `intcalc' by a case switch for zero, positive and negative
numbers.
Yours sincerely
Heiko <[log in to unmask]>
