CFLib.org – Common Function Library Project

Description:
DecimalFormat incorrectly rounds certain numbers, e.g. alterating between rounding up/down the same number at different times. This UDF is an attempt to correct that.

Return Values:
Returns a number.

Example:

<cfset Total = 599>
<cfset VAT = Total * 0.175>
<cfset GrandTotal = Total + VAT>

<cfoutput>
Using DecimalFormat (proof of the bug): <br>
Total: #DecimalFormat(Total)#<br>
Vat: #DecimalFormat(VAT)#<br>
Grand Total: #DecimalFormat(GrandTotal)#<br>
#DecimalFormat(104.825)#<br>
#DecimalFormat(703.825)#<br> 
<br>
Using DecimalFormatCorrectly:<br>
Total: #DecimalFormatCorrectly(Total)#<br>
Vat: #DecimalFormatCorrectly(VAT)#<br>
Grand Total: #DecimalFormatCorrectly(GrandTotal)#<br>
#DecimalFormatCorrectly(104.825)#<br>
#DecimalFormatCorrectly(703.825)#<br>
</cfoutput>

Parameters:

Full UDF Source:

<cfscript>
/**
 * Corrects rounding bug in DecimalFormat.
 * Minor update.
 * 
 * @param number 	 The number to format. (Required)
 * @return Returns a number. 
 * @author duncan cumming (&#100;&#117;&#110;&#99;&#97;&#110;&#46;&#99;&#117;&#109;&#109;&#105;&#110;&#103;&#64;&#97;&#108;&#105;&#101;&#110;&#97;&#116;&#105;&#111;&#110;&#100;&#101;&#115;&#105;&#103;&#110;&#46;&#99;&#111;&#46;&#117;&#107;) 
 * @version 2, October 12, 2004 
 */
function DecimalFormatCorrectly(number) {
	var lhs=0;
	var rhs=0;
	var decLen = 0;
	var i = 0;
	
	if(ListLen(number, ".") EQ 2) {	//xxx.xxx
		lhs = ListFirst(number, ".");
		rhs = ListLast(number, ".");
	} else if (Find(".", Trim(number)) EQ 1) { // .xx
		rhs = number;
	} else if (Find(".", Trim(number)) EQ 0) {	// xx
		lhs = number;
	} else {
		return number;
	}
	
	if (NOT IsNumeric(lhs) OR NOT IsNumeric(rhs)) return number;
	
	for (i = 0; i LT 2; i=i+1) {
		if (Len(rhs) LT 2) rhs = rhs & "0";
	}
	
	// count how many digits > 2dp there are
	decLen = Len(rhs) - 2; 

	// divide by this number of zeroes
	for (i = 0; i LT decLen; i=i+1) {
		rhs = rhs / 10;
	} 

	// round it
	rhs = Round(rhs);

	if (rhs GTE 100) { 
		rhs = 0;
		lhs = lhs + 1;
	}

	// pad with zeros if necessary
	if (rhs LT 10) {
		rhs = "0" & rhs;
	}	
	
	lhs = NumberFormat(lhs);
	
	return (lhs & "." & rhs);
}
</cfscript>