Formatting Numbers for Output

Formatting Numbers for Output

Formatting numbers becomes especially important for HTML output. XSL Transformations provide several elements and functions that convert numeric formats to readable strings. In this section, we'll cover two of these methods to give you a taste of what's possible: <xsl:decimal-format> and the format-number() function.

<xsl:decimal-format>

The <xsl:decimal-format> function defines the characters and symbols used by the format-number() function when converting numbers to human readable strings, as shown by Listing 2.21.

Listing 2.21 Syntax for the <xsl:decimal-format > Element

 <!-- Category: top-level-element -->  <xsl:decimal-format    name = qname    decimal-separator = char    grouping-separator = char    infinity = string    minus-sign = char    NaN = string    percent = char    per-mille = char    zero-digit = char    digit = char    pattern-separator = char /> 

All the attributes are optional and are defined in Table 2.10.

Table 2.10. Decimal-Format Attribute Definitions

Attribute	Value	Default	Description
name	QName	n/a	The name of the format that, if omitted, specifies the default decimal format.
decimal separator	Character	.	Separates the integral and decimal parts of a number.
grouping separator	Character	,	Separates groups of numbers.
infinity	String	Infinity	String that represents the value infinity.
minus sign	Character		Indicates negative numbers.
NaN	String	NaN	String that represents the value NaN (not a number).
percent	Character	%	Indicates percentages.
per-mille	Character	%	Indicates per-mille (per thousand).
zero digit	Character		Indicates where a digit is required.
digit	Character	#	Indicates where a digit might appears unless it's a leading or trailing zero
pattern separator	Character	;	Indicates the separator for positive and negative format patterns.

format-number() Function

The format-number ( number , format , name ) function converts numbers into human readable strings. The <xsl:decimal-format> element utilizes this function to provide the format for the string. This function draws on the formatting specification defined in Java 1.1. For detailed information, that is the place to look.

The three arguments are defined as follows :

• number . This is the numeric input value.

• format . This is a format pattern string explained later in this chapter.

• name . This is the name ( QName ) string of a decimal format created by the <xsl:decimal-format> element. If no named format is present, a default decimal-format is used. A default format is provided by specifying a <xsl:decimal-format> element and not giving it a name.

Although you can use <xsl:decimal-format> to use any character you want for the following values, the default is given. The characters used in specifying the output format are given in Table 2.11. Examples of the usage of different formatting functions are given in Table 2.12.

Table 2.11. Formatting Characters

Character	Default	Description
Zero-digit		A digit always appears at this point.
Digit	#	A digit may appear at this point unless it's a leading or trailing zero.
Decimal point	.	Separates the integral and decimal parts of a number.
Grouping separator	,	Separates groups of numbers.
Minus sign	-	Indicates negative numbers.
Percent sign	%	A number multiplied by 100 and shown as a percent.
Per-mille	%	A number multiplied by 1,000 and shown as per-mille.
Pattern separator	;	Separates the positive and negative format patterns. This enables you to specify separate patterns for each. See the examples.
Apostrophe	'	Escapes special characters in the output so that no translation takes place. To have an output of "**94" use the format pattern '**'00.
E	n/a	Separates mantissa and exponent in scientific notation.
	n/a	The universal currency symbol (#xA4), which must be in single quotes (different Java versions handle this differently).

Table 2.12. Formatting Examples

Number	Format Pattern	Result
5678.9	#,#00.00	5,678.90
1000000	#,##0.0#	1,000,000.0
0567	#,##0.0#	567.0
.33	#00%	33%
-4.5	#0.0#;(#0.0#)	(4.5)