9.6 Compound If Statements

Compound statements contain two or more conditions that JAWS evaluates before your script continues processing. There are two types of compound If statements:

The type of compound statement you use within your script is based largely on the type of processing that needs to occur under certain situations. Compound statements can often replace nested If statements.

Compound Statements Using "And"

A compound statement joined by “and” evaluates two or more conditions before processing continues. All conditions must be true before the entire If statement is said to be true. If JAWS determines that one of the conditions is false, then the entire If statement is considered to be false. You use two ampersands (&&) placed next to each other to indicate a compound statement joined by “and.”

Example 1: A compound statement joined by “and”

Var
Int iValue
Let iValue = CalculateNumber (); Assign a number to iValue
If iValue > 5 && iValue < 10 Then
SayFormattedMessage (OT_MESSAGE, “The value is between 5 and 10.”)
Else
SayFormattedMessage (OT_MESSAGE, “The value is not between 5 and 10.”)
EndIf

In the above example, the compound statement determines if the value stored in iValue is between 5 and 10.

Compound Statements Using "Or"

A compound statement joined by “or” evaluates two or more conditions before processing continues. Any of the conditions can be true to make the entire If statement true. If JAWS determines that none of the conditions are true, then the entire If statement is false. You use two vertical bars (||) placed next to each other to indicate a compound statement joined by “or.”

Example 2: A compound statement joined by “or"

If iValue == 5 || iValue == 10 Then
SayFormattedMesssage (OT_MESSAGE, “The value is either equal to 5 or 10.”)
Else
SayFormattedMessage (OT_MESSAGE, “The value is not equal to either 5 or 10.”)
EndIf

In the above statement, the compound statement determines if the value stored in iValue is equal to 5 or 10.

Short Circuit Evaluation

JAWS uses a feature called short circuit evaluation to speed up the execution of scripts. This feature keeps JAWS from having to evaluate all parts of the expression whether it is needed or not. Short circuit evaluation works by evaluating an expression for an "or condition" such that if the first variable condition is true there is no need to evaluate the second variable condition. In an "and condition," if the first variable condition is false then there is no need to evaluate the second condition.

Consider the following if condition:

If (function1() || function2()) then

In versions of JAWS prior to 5.0, both function1 and function2 would be executed even if function1 returned TRUE. Now however, if function1 returns true then function2 is not executed. In this example, function2 is only executed if function1 returns false. Similarly:

If (f1() && f2()) then

If f1 returns false, f2 will not be evaluated because it will not be possible for both sides of the "and" expression to be true. The function f2 will only be executed if f1 returns true.

 

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