If

If

If[cond] ... Else ... End checks the condition and executes a script block based on the result.

Note

If an expression in an if statement is indeterminate, it is treated as if it were True.

Usages

If[cond] ... End

If[cond] ... End executes the script at ... unless cond evaluates to False.

Example in
The script at ... is not executed, given x==4 is False. x:=3
If[x==4]
   ...
End
The script at ... is executed, given x==4 is indeterminate. If[x==4]
    ...
End

If[cond] ... Else ... End

If[cond] ... Else ... End executes the script after If, if cond evaluates to True. If cond evaluates to False, it executes the script after Else instead.

Example in
The Else block is executed, given x==4 is False. x:=3
If[x==4]
    ...
Else
    ...
End
The If block is executed, given x==4 is indeterminate. If[x==4]
    ...
Else
    ...
End

If[cond1] ... ElseIf[cond1] ... Else ... End

If[cond1] ... ElseIf[cond1] ... Else ... End executes the script after If, if cond1 evaluates to True. If cond1 evaluates to False, but cond2 evaluates to True, it executes the script after ElseIf instead. If both cond1 and cond2~ evaluate to False, it executes the script after Else.

Example in
The ElseIf block is executed, given x==4 is False. Next, it will choose to go either for the If or the Else statement of the inner block. x:=3
If[x==4]
    ...
ElseIf[x==2]
    ...
Else
    ...
End