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

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

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

Composing 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.