George Peter Staplin July 3 2008 -- Here is a simple package for handling money without floating point. It may not be ideal for everyone -- yet. Feel free to improve this, and extend this page.

It could probably use a money-precision command for setting the precision of the numbers after the decimal point.

JMN This might be a nice start for the API - but as it stands it's wildly inaccurate.

e.g calculate 10% tax on 19.11

%package require money 1.0 %money-value [money/ [money 19.11] 10] 1.1

The point of a money package should not be so much to avoid floating-point operations at all cost - but to operate at a level where the errors are at a minimum and you choose when and with what method you do your rounding. e.g by using cents or even some fraction of a cent as your basic unit for calculation and storage.

Other languages seem to have pushed towards a Decimal datatype for currency work.

Martyn Smith My simple solution was to do all math using integer cents/centimes values and just to display a ./, in the right place when displaying any values, the integer math is very quick and no rounding problems.

#By George Peter Staplin #Use it, share it, modify it, don't blame me. package provide money 1.0 proc money value { lassign [split $value .] dol cents set dol [expr {$dol + ($cents / 100)}] set cents [expr {$cents % 100}] list $dol $cents } proc money-value m { join $m . } proc money-pretty m { return \$[join $m .] } proc money+ {a b} { lassign $a adol acent lassign $b bdol bcent set dollars [expr {$adol + $bdol}] set cents [expr {$acent + $bcent}] set dollars [expr {$dollars + ($cents / 100)}] set cents [expr {$cents % 100}] list $dollars $cents } proc money- {a b} { lassign $a adol acents lassign $b bdol bcents set cents [expr {$acents - $bcents}] if {$cents < 0} { incr adol -1 set cents [expr {$cents + 100}] } set dollars [expr {$adol - $bdol}] list $dollars $cents } proc money* {a integer} { lassign $a adol acent set dollars [expr {$adol * $integer}] set cents [expr {($acent * $integer)}] set dollars [expr {$dollars + ($cents / 100)}] set cents [expr {$cents % 100}] list $dollars $cents } proc money/ {a integer} { lassign $a adol acent set cents [expr {$acent / $integer}] set dollars [expr {$adol / $integer}] list $dollars $cents } set cd [money 12.45] set car [money 3999.99] puts "CD + CAR [money-value [money+ $cd $car]]" puts [money-value [money* [money+ $cd $car] 2]] puts "44.02 - 12.99: [money-value [money- [money 44.02] [money 12.99]]]" puts "42.0 / 4: [money-value [money/ [money 42.0] 4]]" puts "45.5 / 3: [money-value [money/ [money 45.5] 3]]" puts "42.0 * 42 * 42 = You're rich! = [money-pretty [money* [money* [money 42.0] 42] 42]]"