The If...Then...Else statement is fundamental to many programming languages. In Intent language, this statement can appear in several different forms.
In the most simple form, a statement block is executed when a boolean test expression is evaluated as True. The following example supplies the FootType rule with a value of :RoundFoot, if a parameter Load has a value less than 12.
If Load < 12 Then FootType = :RoundFoot End If
By adding an Else clause to the statement, the If statement can execute a different statement block if the boolean test expression is evaluated as False.
If Load < 12 Then FootType = :RoundFoot Else FootType = :SquareFoot End If
Adding an ElseIf clause allows you to test multiple boolean expressions. There is no limit to the number of ElseIf clauses in an If statement. The optional Else clause will execute its statement block if none of the boolean test expressions evaluate as True.
If Load < 12 Then FootType = :RoundFoot ElseIf Load < 100 Then FootType = :SquareFoot Else FootType = :RoundTransitionFoot End If
If expression is a single line If...Then...Else expression that can be inserted anywhere that an expression is permitted. As an expression, it must always return a value. Therefore, an Else clause is required. If expressions must always be enclosed by parentheses.
The following example shows an If expression being used in a child rule. The child Foot will instantiate as either a :RoundFoot or :SquareFoot part, depending on the value of the Load parameter.
Child Foot As (If Load < 12 Then :RoundFoot Else :SquareFoot) End Child