Elements of ColdFusion Expressions

Integers

Numbers with no decimal point.

Real numbers

Numbers with a decimal part. Also known as floating point numbers.

The range of ColdFusion numbers is approximately ±10300, or ±1 with 300 zeros after it. Most operations are accurate to 12 digits after the decimal point.

ColdFusion supports scientific notation.

Strings

Text values, which can be enclosed in single (') or double (") quotes. Strings length is limited only by the amount of available memory on the ColdFusion server.

To use a single quote inside a string that is single quoted, escape the single quote by using two single quotes. You can similarly escape a double quote inside a double quote-enclosed string.

To insert a pound sign in a string, the pound sign must be escaped, or doubled,

Boolean values

The result of a logical operation. Their value can be either TRUE or FALSE. The numerical value of TRUE is 1. The numerical value of FALSE is 0. When converted to a string, TRUE becomes "YES" and FALSE becomes "NO".

Date values

Date-and-time values identify a date and time in the range 100AD to 9999AD. If no time part is specified, time is set to 12:00am.

You can also directly enter a date object in any of the following formats:

"October 30, 1999"
"Oct 30, 1999"
"Oct. 30, 1999"
"10/30/99"
"1999-30-10"

Time values

You can directly enter a date-and-time object in any of the following formats:

"October 30, 1999 02:34:12"
"October 30, 1999 2:34a"
"October 30, 1999 2:34am"
"October 30, 1999 02:34am"
"October 30, 1999 2am"

The time part of the object is accurate to the second.

Lists

Lists are a special kind of string, made up of elements separated by delimiters.

You specify the allowable delimiters for a list by [HOW?] A list can have more than one delimiting character. The default delimiting character, used by all list processing functions is a comma: ",". White space is not considered a delimiter. However, when using lists where elements may be separated by white space as well as other delimiters, be sure to add the white space characters to the delimiters. Delimiters before the first element and after the last element are ignored.

The structure of lists is flat - that is, lists cannot be nested into one another. Also, lists can contain no "empty" elements. A list can be empty, however. The empty list is equivalent to the empty string "".

Structures

You can use structures to create and maintain key-value pairs, to refer to related string values as a unit rather than individually, or to create associative arrays.

For more information about structures, see Developing Web Applications with ColdFusion.

Arrays

Arrays are tables of objects or data that can be indexed. Although the ArrayNew function only supports creating up to three-dimensional arrays, there is no limit on array size or maximum dimension.

Elements stored in an array are referenced as follows:

<CFSET myarray[1][2]=Now()>

For more information about arrays, see Developing Web Applications with ColdFusion.

Queries

ColdFusion queries can be referenced as objects by assigning a query to a variable:

<CFQUERY NAME=myquery
    DATASOURCE=mydata
    SELECT * FROM CUSTOMERS
</CFQUERY>

<CFSET myquery2=myquery>

In this case (unlike the same operation with arrays) the query is not copied. Instead, both names point to the record set data so that if you make changes to the table referenced in the query, the original query and the query object myquery2 will both reflect those changes.

Queries and variables cannot have the same name at the same time in the same application page.

COM objects

COM (Component Object Model) objects are non-visual components that encapsulate specific functionality you can invoke in your application pages. ActiveX, OCX, CORBA, and ADO objects are examples of COM objects.

COM objects generally contain methods, like functions, you can use to execute certain operations:

<CFSET temp=Mailer.SendMail()>

COM objects also generally contain properties you can read and write using ColdFusion variables:

<CFSET Mailer.FromName=Form.fromname>

Properties can be invoked on either side of an assignment.

For more information about COM objects, see Developing Web Applications with ColdFusion.

Variables