How to nest a if state ment in a case?

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Eminent

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Posted: 21st Oct 2010 04:23

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I've been trying to do this but the compiler keeps giving me errors.

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Coldfire

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Posted: 21st Oct 2010 04:32 Edited at: 21st Oct 2010 04:33

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Well, I tried this:

+ Code Snippet

choice = 1

do
	select choice:
		case 1:
			if mousex() = 0 and spacekey()
				end
			endif
		endcase
	endselect
loop
end]

It didn't throw any errors and seemed to work fine. Can you post a sample perhaps?

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gbark

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Posted: 21st Oct 2010 04:33

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Works fine for me too.

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repeat
    // Get input
    input "Enter a letter (try vowels or consonants): ", userIn$
    
    // SELECT if the input is a vowel
    select upper$(userIn$)
    
        // Case for vowel
        case "A", "E", "I", "O", "U"
        
            // Check capitalization
            if (userIn$ = upper$(userIn$))
                print "Uppercase vowel"
            else
                print "Lowercase vowel"
            endif
            print ""
    
        endcase
        
        // Case for not a vowel
        case default
        
            // Check capitalization
            if (userIn$ = upper$(userIn$))
                print "Uppercase consonant"
            else
                print "Lowercase consonant"
            endif
            print ""
        
        endcase
    
    endselect

// Keep looping as long as the input is not null
until (userIn$ = "")
end

What version of DBPro are you using? Could be that you need to upgrade. Otherwise, it's probably a different error in your code.

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Neco

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Posted: 21st Oct 2010 04:37

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What are you trying to do?

Some code would probably help

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baxslash

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Posted: 21st Oct 2010 14:31 Edited at: 21st Oct 2010 14:33

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I would guess you were trying to do it like this:

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select thingy
   if wotsit=1
      case 1
         print "wotsit is 1 and thingy is 1"
      endcase
      case 2
         print "wotsit is 1 and thingy is 2"
      endcase
   else
      case 1
         print "wotsit is not 1 and thingy is 1"
      endcase
      case 2
         print "wotsit is not 1 and thingy is 2"
      endcase
   endif
endselect

...which would throw an error, whereas:

+ Code Snippet

select thingy
   case 1
      if wotsit=1
         print "wotsit is 1 and thingy is 1"
      else
         print "wotsit is not 1 and thingy is 1"
      endif
   endcase
   case 2
      if wotsit=1
         print "wotsit is 1 and thingy is 2"
      else
         print "wotsit is not 1 and thingy is 2"
      endif
   endcase
endselect

...would not. At least that's as long as I didn't get my "wotsits" and "thingys" mixed up (as I sometimes do!)

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Eminent

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Posted: 22nd Oct 2010 02:22

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+ Code Snippet

	Select upkey()
	  Case 0 : Print "not moving" : Gas = 0 :EndCase
	  Case 1 : move object 1, -3 : inc Gas : if Gas => 10 then move object 1, 10 : Endcase
	endselect

Gives me an out of place error.

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gbark

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Posted: 22nd Oct 2010 03:50 Edited at: 22nd Oct 2010 03:52

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You can't put the ENDCASE on the same line as your IF. Your code works after moving the commands to separate lines. The reason being how DBPro handles IF statements when you use the THEN keyword (which was similar to the problem is this thread, if you want to take a look) Also, you have if Gas => 10 when I think you need if Gas >= 10

+ Code Snippet

Select upkey()
      Case 0
        Print "not moving" : Gas = 0
      EndCase
      Case 1
        move object 1, -3
        inc Gas
        if Gas >= 10 then move object 1, 10
      Endcase
endselect

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Eminent

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Posted: 22nd Oct 2010 03:52

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Thanks man.

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baxslash

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Posted: 22nd Oct 2010 10:30

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Quote: "You can't put the ENDCASE on the same line as your IF"

Not true, you can as long as you use an ENDIF. Using THEN means everything after the THEN (even after colons) is counted in the IF statement.

+ Code Snippet

Select upkey()
      Case 0:Print "not moving" : Gas = 0:EndCase
      Case 1:move object 1, -3:inc Gas:if Gas >= 10:move object 1, 10:endif:Endcase
endselect

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Neco

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Posted: 22nd Oct 2010 16:41

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Sounds like a syntax parsing bug to me. I can't think of why it would want to work that way?

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gbark

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Posted: 22nd Oct 2010 17:24

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Quote: "Not true, you can as long as you use an ENDIF. Using THEN means everything after the THEN (even after colons) is counted in the IF statement."

Yes, you're right about that. I was referring to using the IF-THEN style statement (in which you are forced to separate the lines), rather than IF-ENDIF.

Quote: "Sounds like a syntax parsing bug to me. I can't think of why it would want to work that way?"

Mostly if you have a "short" IF statement that composes of just a few commands in a block. Using the IF-THEN style will cause the rest of the line of code to be associated with that IF block, without you having to explicitly close the block.

So instead of:

+ Code Snippet

if (conditional = value)
  print "moving"
  move object 1, 10
  print "done moving"
endif

You could shorten it to:

+ Code Snippet

if (conditional = value) then print "moving" : move object 1, 10 : print "done moving"

It's not an error, it's just a "shortcut". Problem is that it can introduce errors into your code if you aren't aware of it.

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Neco

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Posted: 22nd Oct 2010 19:12 Edited at: 22nd Oct 2010 19:12

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Hmm.. I only reserve THEN for use when I have a single condition/action to do, so I guess it's just me.

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baxslash

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Posted: 24th Oct 2010 11:20

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Quote: "Hmm.. I only reserve THEN for use when I have a single condition/action to do, so I guess it's just me."

I very rarely use it for more than one action either...

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IanM

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Posted: 24th Oct 2010 16:18

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Quote: "Sounds like a syntax parsing bug to me. I can't think of why it would want to work that way?"

As others have said, that's not so.

Using a THEN is equivalent to adding an ENDIF to the very end of the line.

Your line:

+ Code Snippet

Case 1 : move object 1, -3 : inc Gas : if Gas => 10 then move object 1, 10 : Endcase

is equivalent to:

+ Code Snippet

Case 1 : move object 1, -3 : inc Gas : if Gas => 10 move object 1, 10 : Endcase : Endif

You can see that the ENDCASE is in the middle of the IF statements associated code block.

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DarkBASIC Professional Discussion / How to nest a if state ment in a case?