General information
Operators perform arithmetic calculations; compare numbers, text, and boolean values; execute relational operations on boolean values; and concatenate strings and blobs.
Three types
PowerScript supports three types of operators:
-
Arithmetic operators for numeric datatypes
-
Relational operators for all datatypes
-
Concatenation operator for string datatypes
Operators used in DataWindow objects
The documentation for DataWindows describes how operators are used in DataWindow expressions.
Description
The following table lists the arithmetic operators used in PowerBuilder.
|
Operator |
Meaning |
Example |
|---|---|---|
|
+ |
Addition |
Total=SubTotal+Tax |
|
- |
Subtraction |
Price=Price-Discount Unless you have prohibited the use of dashes in identifier names, you must surround the minus sign with spaces. |
|
* |
Multiplication |
Total=Quantity*Price |
|
/ |
Division |
Factor=Discount/Price |
|
^ |
Exponentiation |
Rank=Rating^2.5 |
Usage
Operator shortcuts for assignments
For information about shortcuts that combine arithmetic operators with assignments (such as ++ and +=), see Assignment.
Subtraction
If the option Allow Dashes in Identifiers is checked on the Script tab in the Options dialog box, you must always surround the subtraction operator and the -- operator with spaces. Otherwise, PowerBuilder interprets the expression as an identifier.
For information about dashes in identifiers, see Identifier names.
Multiplication and division
Multiplication and division are carried out to full precision (16-28 digits). Decimal numbers are rounded (not truncated) on assignment.
Calculation with NULL
When you form an arithmetic expression that contains a NULL value, the expression's value is null. Thinking of null as undefined makes this easier to understand.
For more information about null values, see NULL values.
Errors and overflows
The following problems can occur when using arithmetic operators:
-
Division by zero, exponentiation of negative values, and so on cause errors at runtime.
-
Overflow of real, double, and decimal values causes errors at runtime.
-
Overflow of signed or unsigned integers and longs causes results to wrap. However, because integers are promoted to longs in calculations, wrapping does not occur until the result is explicitly assigned to an integer variable.
For more information about type promotion, see Datatype of PowerBuilder expressions.
Examples
Subtraction
This statement always means subtract B from A:
A - B
If DashesInIdentifiers is set to 1, the following statement means a variable named A-B, but if DashesInIdentifiers is set to 0, it means subtract B from A:
A-B
Precision for division
These examples show the values that result from various operations on decimal values:
decimal {4} a,b,d,e,f
decimal {3} c
a = 20.0/3 // a contains 6.6667
b = 3 * a // b contains 20.0001
c = 3 * a // c contains 20.000
d = 3 * (20.0/3) // d contains 20.0000
e = Truncate(20.0/3, 4) // e contains 6.6666
f = Truncate(20.0/3, 5) // f contains 6.6667Calculations with null
When the value of variable c is null, the following assignment statements all set the variable a to null:
integer a, b=100, c SetNULL(c) a = b+c // all statements set a to NULL a = b - c a = b*c a = b/c
Overflow
This example illustrates the value of the variable i after overflow occurs:
integer i i = 32767 i = i + 1 // i is now -32768
Description
PowerBuilder uses relational operators in boolean expressions to evaluate two or more operands. Logical operators can join relational expressions to form more complex boolean expressions.
The result of evaluating a boolean expression is always true or false.
The following table lists relational and logical operators.
|
Operator |
Meaning |
Example |
|---|---|---|
|
= |
Equals |
if Price=100 then Rate=.05 |
|
> |
Greater than |
if Price>100 then Rate=.05 |
|
< |
Less than |
if Price<100 then Rate=.05 |
|
<> |
Not equal |
if Price<>100 then Rate=.05 |
|
>= |
Greater than or equal |
if Price>=100 then Rate=.05 |
|
<= |
Less than or equal |
if Price<=100 then Rate=.05 |
|
NOT |
Logical negation |
if NOT Price=100 then Rate=.05 |
|
AND |
Logical and |
if Tax>3 AND Ship <5 then Rate=.05 |
|
OR |
Logical or |
if Tax>3 OR Ship<5 then Rate=.05 |
Usage
Comparing strings
When PowerBuilder compares strings, the comparison is case sensitive. Trailing blanks are significant.
For information on comparing strings regardless of case, see the functions Upper and Lower.
To remove trailing blanks, use the RightTrim function. To remove leading blanks, use the LeftTrim function. To remove leading and trailing blanks, use the Trim function. For information about these functions, see RightTrim, LeftTrim, and Trim.
Decimal operands
Relational operators that operate on numeric values (including =, >, <, <>, >=, and <=) can take decimal operands. The precision of the decimal operand is maintained in comparisons.
Null value evaluations
When you form a boolean expression that contains a null value, the AND and OR operators behave differently. Thinking of null as undefined (neither true nor false) makes the results easier to calculate.
For more information about null values, see NULL values.
Examples
Case-sensitive comparisons
If you compare two strings with the same text but different case, the comparison fails. But if you use the Upper or Lower function, you can ensure that the case of both strings are the same so that only the content affects the comparison:
City1 = "Austin" City2 = "AUSTIN" IF City1 = City2 ... // Returns FALSE City1 = "Austin" City2 = "AUSTIN" IF Upper(City1) = Upper(City2)... // Returns TRUE
Trailing blanks in comparisons
In this example, trailing blanks in one string cause the comparison to fail:
City1 = "Austin" City2 = "Austin " IF City1 = City2 ... // Returns FALSE
Logical expressions with null values
In this example, the expressions involving the variable f, which has been set to null, have null values:
boolean d, e = TRUE, f SetNull(f) d = e and f // d is NULL d = e or f // d is TRUE
Description
The PowerBuilder concatenation operator joins the contents of two variables of the same type to form a longer value. You can concatenate strings and blobs.
The following table shows the concatenation operator.
Examples
Example 1
These examples concatenate several strings:
string Test
Test = "over" + "stock" // Test contains "overstock"
string Lname, Fname, FullName
FullName = Lname + ', ' + Fname
// FullName contains last name and first name,
// separated by a comma and space.Example 2
This example shows how a blob can act as an accumulator when reading data from a file:
integer i, fnum, loops blob tot_b, b . . . FOR i = 1 to loops bytes_read = FileRead(fnum, b) tot_b = tot_b + b NEXT
