MACROMEDIA COLDFUSION MX 61-DEVELOPING COLDFUSION MX, Develop Manual, Page: 56 / 860

56 Chapter 3: Using ColdFusion Variables
Data type notes
Although ColdFusion variables do not have types, it is often convenient to use “variable type” as a
shorthand for the type of data that the variable represents.
ColdFusion can validate the type of data contained in form fields and query parameters. For more
information, see
Chapter 26, “Validating form field data types,” on page 579 and Chapter 20,
“Using cfqueryparam,” on page 435 .
The
cfdump
tag displays the entire contents of a variable, including ColdFusion complex data
structures. It is an excellent tool for debugging complex data and the code that handles it.
ColdFusion provides the following functions for identifying the data type of a variable:
•
IsArray
•
IsBinary
•
IsBoolean
•
IsObject
•
IsQuery
•
IsSimpleValue
•
IsStruct
•
IsXmlDoc
ColdFusion also includes the following functions for determining whether a string can be
represented as another simple data type:
•
IsDate
•
IsNumeric
ColdFusion does not use a null data type. However, if ColdFusion receives a null value from an
external source such as a database, a Java object, or some other mechanism, it maintains the null
value until you use it as a simple value. At that time, ColdFusion converts the null to an empty
string ("").
Numbers
ColdFusion supports integers and real numbers. You can intermix integers and real numbers in
expressions; for example, 1.2 + 3 evaluates to 4.2.
Integers
ColdFusion supports integers between -2,147,483,648 and 2,147,483,647 (32-bit signed
integers). You can assign a value outside this range to a variable, but ColdFusion initially stores
the number as a string. If you use it in an arithmetic expression, ColdFusion converts it into a
floating point value, preserving its value, but losing precision as the following example shows:
<cfset mybignum=12345678901234567890>
<cfset mybignumtimes10=(mybignum * 10)>
<cfoutput>mybignum is: #mybignum#</cfoutput><br>
<cfoutput>mybignumtimes10 is: #mybignumtimes10# </cfoutput><br>
This example generates the following output:
mybignum is: 12345678901234567890
mybignumtimes10 is: 1.23456020