Case 1 < 1 = True?

[Bagel]

I am trying to learn about Select and Case usage with Do loops and I'm having a very difficult time understanding my results. When I run this code using the hotkey the first case executes twice but I can't see how. It's as if the Select statement pulls 0 as the value for $variable every time but then uses the new value as it increments within the case.

 

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#include <WinAPISysWin.au3>
#include <WindowsConstants.au3>
#include <Inet.au3>
#Include <File.au3>
#include <FileConstants.au3>
#include <WinAPIFiles.au3>
#include <TrayConstants.au3>
#include <Date.au3>

#pragma compile(inputboxres, true)

HotKeySet("!t", "Main")

While 1
   Sleep(50)
WEnd

Func Main()
        $variable = 0

        CaseTest( $variable )
EndFunc


Func CaseTest ( ByRef $variable )

    Do
        ConsoleWrite( "$variable, " & $variable & ". BEGIN SELECT STATEMENT." & @CRLF )
        Select
            Case $variable < 1 < 2
                ConsoleWrite( "The condition for the FIRST case returned true and $variable, " & $variable & ", should still be 0." & @CRLF )
                Do

                    ConsoleWrite( "$variable, " & $variable & ", should still be 0 here." & @CRLF )
                    $variable = $variable + 1
                    ConsoleWrite( "$variable, " & $variable & ", should now be 1." & @CRLF )

                Until $variable = 1
                ConsoleWrite( "The Do loop in the FIRST case is complete and $variable, " & $variable & ", should be 1." & @CRLF )
            Case 0 < $variable < 2
                ConsoleWrite( "The condition for the SECOND case returned true and $variable, " & $variable & ", should still be 1." & @CRLF )
                Do

                    ConsoleWrite( "$variable, " & $variable & ", should still be 1 here." & @CRLF )
                    $variable = $variable + 1
                    ConsoleWrite( "$variable, " & $variable & ", should now be 2." & @CRLF )

                Until $variable = 2
                ConsoleWrite( "The Do loop in the SECOND case is complete and $variable, " & $variable & ", should be 2." & @CRLF )
            Case 0 < 1 < $variable
                ConsoleWrite( "The condition for the THIRD case returned true and $variable, " & $variable & ", should still be 2." & @CRLF )
                Do

                    ConsoleWrite( "$variable, " & $variable & ", should still be 2 here." & @CRLF )
                    $variable = $variable + 1
                    ConsoleWrite( "$variable, " & $variable & ", should now be 3." & @CRLF )

                Until $variable = 3
                ConsoleWrite( "The Do loop in the THIRD case is complete and $variable, " & $variable & ", should be 3." & @CRLF )
        EndSelect
        ConsoleWrite( "$variable, " & $variable & ". END OF SELECT STATEMENT." & @CRLF )
    Until $variable = 3
    ConsoleWrite( "$variable, " & $variable & ". END OF TOP DO LOOP." & @CRLF & @CRLF )

EndFunc ; CaseTest

 

[Bagel]

Just to clarify a bit.. I understand why the Do loop in the first Case recycles infinitely. However, the second time around the first statement in that case reports that the function KNOWS that $variable = 1 BEFORE the Do loop is executed. The only way I can see for that to happen is if "1 < 1" returns TRUE.

[jchd]

You're misusing the comparison operator.

$variable < 1 < 2

Starting with $variable = 0, the expression evaluates from left to right:
$variable < 1 < 2
0 < 1 < 2
(0 < 1) < 2
True < 2
The < operator forces conversion to numeric here
1 < 2
which yields
True
which itself evaluates to 1

At the next iteration, $variables = 1 but:
$variable < 1 < 2
1 < 1 < 2
(1 < 1) < 2
False < 2
The < operator forces conversion to numeric here
0 < 2
which yields
True
which itself evaluates to 1 (again)

That's why you never exit the loop albeit $variable increases to signed 64-bit infinity.

You want

Switch $variable
    Case 0
        ...
    Case 1
        ...
    Case 2
        ...
    Case 3
        ...
    Case Else
        ...
EndSwitch

 

[Bagel]

Actually, I really needed to use the compound comparison. After playing with it I found I could achieve the result I was hoping for by using parentheses and "And". My mind was really bent on a more compact form though as the code I'm using this logical structure for is a lot more involved. It's ironic that the simplest way I could think of to test how this all worked ended up being the obstacle to my understanding it. Thanks for the help!