top of the atomic type hierarchy is xdt:anyAtomicType, whose subtypes are the primitive types. in Font

Printing PDF417 in Font top of the atomic type hierarchy is xdt:anyAtomicType, whose subtypes are the primitive types.

You ve already seen how to create some kinds of atomic values using simple expressions. To create a string, you just use the value of the string that you want, with quotes around it; for example, to create the xs:string value 'StarTrek' you use either of the following: 'StarTrek' "StarTrek"

Including quotes in string literals has traditionally been a problem in XSLT. Say that you wanted to test whether a string contains an apostrophe. To test that, you need to create a string that contains a single apostrophe character. If you delimit the string literal with apostrophes, as in contains(Name, ''') then the processor will interpret the apostrophe character in the string as ending the string literal, and will complain that the XPath expression isn t legal. You can use double quotes around the apostrophe instead: contains(Name, "'") But then, what if you need to create a string that contains both an apostrophe and a double quote If you delimited the string literal with apostrophes, the apostrophe in the string would be interpreted as the end of the string literal; if you delimited it with double quotes, the double quote in the string would be interpreted as the end of the string literal.

To get around this problem, XPath 2.0 allows you to escape apostrophes or double quotes within a string by doubling them. For example, the following call to the contains() function would be legal: contains(Name, '''') Another level of complication arises because these expressions are embedded in XML attribute values, which themselves use either apostrophes or double quotes as delimiters. It s not well-formed XML to include a double quote inside an attribute value that s delimited by double quotes. For example, the following isn t well-formed XML: <xsl:if test="contains(Name, "'")">...</xsl:if> If an attribute value is delimited by double quotes, then you have to escape any double quotes within the attribute value using the XML escape ". Likewise, if an attribute value is delimited by apostrophes, then you have to escape any apostrophes within the attribute value using the XML escape '. So the following are all legal ways of testing whether the <Name> element child of the current node contains an apostrophe, both at the XML level and the XPath level: <xsl:if <xsl:if <xsl:if <xsl:if test="contains(Name, test='contains(Name, test="contains(Name, test='contains(Name, "'")">...</xsl:if> "'")'>...</xsl:if> '''')">...</xsl:if> '''')'>...</xsl:if>

To create a number, you just include the number literally; for example, to create the number 6, you can just use 6 In fact, this literal creates a value of type xs:integer. To create values of other numeric types, you need to use slightly different syntax. To create a value of type xs:decimal, you need to include a decimal point: 6.0 To create a value of type xs:double, you need to include an exponent; any of the following will create the xs:double value 6E0: 6E0 6.0E+0 6e0 0006e0

Note When creating a number with a numeric literal, you can include whatever leading or trailing zeros

To create values of any other type, it s usually easiest to use a constructor function. Constructor functions are special functions that are designed for constructing atomic values. Each is named after the type of value that it constructs, and takes a single argument, usually a string, which specifies the value. For example, to create the xs:time 18:00:00, you would use xs:time('18:00:00')

Caution You will get an error if the argument you pass to a constructor function isn t a legal value for the

In most cases, the string that you pass in as the argument to the constructor function can come from anywhere: it can be a string literal; the value of a node; or a substring of another string, calculated using the substring() function, for example. So the following is perfectly fine: xs:time(concat(substring(dc:date, 17, 5), '00')) However, for arcane implementation-related reasons, the xs:QName constructor function (and the xs:NOTATION constructor function, which you will never use) can only be called with an argument that is a string literal. Thus, the following works: xs:QName('xs:string') but the following gives an error because the argument is not a string literal: xs:QName(concat('xs', ':', 'string'))

Note The string literal passed as the argument of xs:QName() will be interpreted based on the namespace declarations that are present in your stylesheet. If the string doesn t have a prefix, then the default namespace for element and type names, which is set using the xpath-default-namespace attribute, will be used. If there s no xpath-default-namespace attribute, then the unprefixed string will be interpreted as being a local name only (in no namespace). The default namespace declared in the stylesheet is never used.

Using constructor functions is actually a specialized form of casting, which we ll look at in the next section.

Summary Strings and numbers can be created using literals. Values of other types are usually created

using constructor functions, each of which has the same name as the type that they re used to create.