# Re: Bug in expr ?

*From*: Michael Schlenker <schlenk@xxxxxxxxxxxxxxxx>*Date*: Sun, 02 Jul 2006 22:35:33 +0200

tunity5@xxxxxxxxx schrieb:

stephanearnold@xxxxxxxx wrote:So use floating point arithmetics and force rounding in a way you like.

Hi,

IMHO there is no relation with floats. It is the rule that, given A & B

positive,

(A modulo B) and (-A modulo B) cannot be negative. (it is a convention)

I don't follow you wrote.

Perhaps, I can provide some background into how I came across this

behavior:

########## find out how many days between any two dates

########## specifically, number of 24-hour spans between them

######### set up

set one_day [expr 60 * 60 * 24]

set today [clock seconds]

set yesterday [clock scan "july 2, 2006"]

#### ordering #1

% expr ($today - $yesterday) / $one_day

0

#### ordering #2

% expr ($yesterday - $today) / $one_day

-1

So, the question is, what is the answer? Note that I am OK with either

answer (0 or 1), depending on what you view as a "day" but I would like

to get the same result from both expressions.

Michael

.

**References**:**Bug in expr ?***From:*tunity5

**Re: Bug in expr ?***From:*Michael Schlenker

**Re: Bug in expr ?***From:*tunity5

**Re: Bug in expr ?***From:*Eric Hassold

**Re: Bug in expr ?***From:*tunity5

**Re: Bug in expr ?***From:*stephanearnold

**Re: Bug in expr ?***From:*tunity5

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