Expression syntax

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Expressions are used for calculating numerical values, strings or logical values ("true" or "false"). There are various operators and functions available for this, comparable to a programming language ("Pascal" in this case), which can be used to do many kinds of calculations. You can do operations with data fields, for example calculate the tax for a given amount, or merge two data fields into one string. Please note that if the expression is a property of a report band, the result of the expression must be a logical value. Only the group band expects the result to be a string or a number, just like the expression-field report-element.

Composing expressions

The expression evaluator is working with four data types: Strings, Integer, Float and Boolean. Binary data and memo fields are not supported in expressions. Below is a list of how database fields are converted to report data types:

Data type	Field type
String	String fields, date and time fields
Integer	SmallInt fields, byte fields, integer fields
Float	Float fields, currency fields
Boolean	Boolean (logical) fields

   

Report expression syntax is very much like Object Pascal. Below is a list of supported operators:

Operator	Description
+	Add
-	Subtract
*	Multiply
/	Divide
()	Parentheses
And	Logical AND
Or	Logical OR
Not	Logical NOT
=	Equal
<	Less than
>	Greater than
<=	Less than or equal
>=	Greater than or equal
<>	Not equal

The standard functions included are:

Function	Description
Date	Return current date as a string
Time	Return current time as a string
Str(Number)	Converts the numeric argument to a string
Copy(Str,s,l)	Returns a substring of str (starting from the s-th character, returning a maximum of l characters)
Int(Number)	Returns the integer part of a number
Frac(Number)	Returns the fractional part of a number
If (Expr, r1, r2)	Returns r1 or r2 depending on the boolean expr
TypeOf(Expr)	Returns the data type of expr
Sqrt(Number)	Returns the square root of a number
True	Logical value True
False	Logical value False
Sum(Expr)	Returns the sum of expr
Count	Returns the number of entires
Min(Expr)	Returns the lowest value of expr
Max(Expr)	Returns the highest value of expr
Average(Expr)	Averages the expr

   
             
Using database fields in expressions
Any field in any table referenced in your report can be accessed in an expression. Field names can be referenced either just by the field name itself (e.g. Name) or by the table name followed by a dot and the field name (e.g. Customers.Name). If you do not specify a table name the report engine will search for the field in all available data sets and use the first instance found.

The current version of the expression evaluator does not support field names with embedded special characters like blank, "/", dot, dollar sign and so on.

Using Strings in Expressions
Strings in expression should be put in single quotes. The following is a valid expression:

"Computers are great!"

Maximum string length is 255 characters.

Expression Examples
Below are some examples of expressions:

Expression	Description
1	Integer constant, returns 1
1.5	Floating point constant, returns 1.5
"Delphi"	String constant, returns "Delphi" as a string
True	Logical constant, returns True
1 + 2	Numeric calculation, returns 3
2 * (3 + 2.5)	Numeric calculation, returns 11
"Delphi" + " is great"	String calculation, returns "Delphi is great"
Name	Returns the value of the field Name if it exists
Customer.Name	Returns the value of the field Name in the Customer table
Name + " " + Contact	Adds the Name field, a blank and the Contact field
AmountPaid * TaxRate / 100	Numeric field calculation
"Printed "+ Date	String calculation
"Total amount paid is " + str(AmountPaid)	String calculation
if(AmountPaid > 5000, "Large order", "Small order")	Returns "Large order" if AmountPaid is greater than 5000, else "Small order"
if(CheckField, "X", " ")	Prints an X if CheckField is True

Compose expressions visually
Expressions can be typed in directly to the corresponding edit line, or you can press the button ".." to the right of the edit line to show the expression builder dialog. You can then visually design your expression with your mouse. If a used function has parameters, like "Copy" or "Sum", another copy of the dialog will be opened to define those parameters separately.