Help with case statement and constants

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Death_fox

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Posted: 8th Nov 2012 21:06

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yo, i been trying to use a variable for a case statement but didn't work, i did some reseach and found out that constants do work with case statments but when i try i just returned the "CASE needs a literal parameter" error

here's my code.

select world(X_loop + top_left_block.X,Y_loop + top_left_block.Y).block
					
					case (Stone) `surface rock
						ink RGB(96,99,61),0
						box block_cord.X,block_cord.Y,block_cord.X+block_size,block_cord.Y+block_size						
					endcase
					case (Concrete_floor) `floor
						ink RGB(192,192,192),0
						box block_cord.X,block_cord.Y,block_cord.X+block_size,block_cord.Y+block_size
					endcase
			
					case (wall) ` wall
						ink RGB(192,192,192),0 `floor
						box block_cord.X,block_cord.Y,block_cord.X+block_size,block_cord.Y+block_size
						
						ink RGB(55,55,55),0
						box int(block_cord.X + (block_size/3)),int(block_cord.Y + (block_size/3)),int((block_cord.X+block_size) - (block_size/3)),int((block_cord.Y+block_size) - (block_size/3))
						`north
						if world(X_loop+ top_left_block.X,Y_loop+ top_left_block.Y).connectN = true
							box int(block_cord.X + (block_size/3)),block_cord.Y,int((block_cord.X+block_size) - (block_size/3)),int((block_cord.Y+block_size) - (block_size/3))
						endif
						`east
						if world(X_loop+ top_left_block.X,Y_loop+ top_left_block.Y).connectE = true
							box block_cord.X ,int(block_cord.Y + (block_size/3)),int((block_cord.X+block_size) - (block_size/3)),int((block_cord.Y+block_size) - (block_size/3))
						endif
						`south
						if world(X_loop+ top_left_block.X,Y_loop+ top_left_block.Y).connectS = true
							box int(block_cord.X + (block_size/3)),int(block_cord.Y + (block_size/3)),int((block_cord.X+block_size) - (block_size/3)),block_cord.Y+block_size
						endif
						`west
						if world(X_loop+ top_left_block.X,Y_loop+ top_left_block.Y).connectW = true
							box int(block_cord.X + (block_size/3)),int(block_cord.Y + (block_size/3)),block_cord.X+block_size,int((block_cord.Y+block_size) - (block_size/3))
						endif
					endcase
			
			
			endselect

+ Code Snippet

		select world(X_loop + top_left_block.X,Y_loop + top_left_block.Y).block
					
					case (Stone) `surface rock
						ink RGB(96,99,61),0
						box block_cord.X,block_cord.Y,block_cord.X+block_size,block_cord.Y+block_size						
					endcase
					case (Concrete_floor) `floor
						ink RGB(192,192,192),0
						box block_cord.X,block_cord.Y,block_cord.X+block_size,block_cord.Y+block_size
					endcase
			
					case (wall) ` wall
						ink RGB(192,192,192),0 `floor
						box block_cord.X,block_cord.Y,block_cord.X+block_size,block_cord.Y+block_size
						
						ink RGB(55,55,55),0
						box int(block_cord.X + (block_size/3)),int(block_cord.Y + (block_size/3)),int((block_cord.X+block_size) - (block_size/3)),int((block_cord.Y+block_size) - (block_size/3))
						`north
						if world(X_loop+ top_left_block.X,Y_loop+ top_left_block.Y).connectN = true
							box int(block_cord.X + (block_size/3)),block_cord.Y,int((block_cord.X+block_size) - (block_size/3)),int((block_cord.Y+block_size) - (block_size/3))
						endif
						`east
						if world(X_loop+ top_left_block.X,Y_loop+ top_left_block.Y).connectE = true
							box block_cord.X ,int(block_cord.Y + (block_size/3)),int((block_cord.X+block_size) - (block_size/3)),int((block_cord.Y+block_size) - (block_size/3))
						endif
						`south
						if world(X_loop+ top_left_block.X,Y_loop+ top_left_block.Y).connectS = true
							box int(block_cord.X + (block_size/3)),int(block_cord.Y + (block_size/3)),int((block_cord.X+block_size) - (block_size/3)),block_cord.Y+block_size
						endif
						`west
						if world(X_loop+ top_left_block.X,Y_loop+ top_left_block.Y).connectW = true
							box int(block_cord.X + (block_size/3)),int(block_cord.Y + (block_size/3)),block_cord.X+block_size,int((block_cord.Y+block_size) - (block_size/3))
						endif
					endcase
			
			
			endselect

thinking about it, it might be the way i'm declearing the constants so heres there declaration as well.

+ Code Snippet

	`#constant <block name> create_block("<block name>",<hardness>,<volumn>,<mass>,<is solid>)
	#constant Air Create_block("Air",0,1,0,false)

the Create_block function returns a integer

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The Weeping Corpse

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Joined: 19th Sep 2011

Location: United Kingdom

Posted: 8th Nov 2012 22:40 Edited at: 8th Nov 2012 23:12

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You can't place executable code within a constant declaration

#constant mytest = 1 is fine

#constant mytest myfunction(....) is no no in darkbasic

WAIT, yes you can, I'm just very tired lol.

www.youtube.com/user/TheWeepingCorpse

www.theweepingcorpse.com

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Green Gandalf

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Joined: 3rd Jan 2005

Playing: Malevolence:Sword of Ahkranox, Skyrim, Civ6.

Posted: 9th Nov 2012 00:20

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The parameter used in a case statement must be a literal - as the compiler is telling you.

If you use a constant as the parameter then that must be a literal too at compile time. Like this:

+ Code Snippet

#constant myConstant "2" `define the constant to be a literal string
key$ = "" ` initialize just in case

print "press a digit 0-9"

print

repeat
  key$ = inkey$()
until key$ <> ""

select key$
  case myConstant
    print "you entered ", myConstant
  endcase
  case default
    print "you did not enter ", myConstant
  endcase
endselect

repeat
until inkey$() = ""

print
print " press a key to exit"
wait key

end

Remember that #constants are replaced by their defined code before the program is compiled for syntax checking etc. It is a simple text replacement as far as the compiler is concerned.

Hence my snippet looks like this when finally compiled:

+ Code Snippet

key$ = "" ` initialize just in case

print "press a digit 0-9"

print

repeat
  key$ = inkey$()
until key$ <> ""

select key$
  case "2"
    print "you entered ", "2"
  endcase
  case default
    print "you did not enter ", "2"
  endcase
endselect

repeat
until inkey$() = ""

print
print " press a key to exit"
wait key

end

#constants are purely a device to aid the programmer.

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Kevin Picone

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Joined: 27th Aug 2002

Location: Australia

Posted: 9th Nov 2012 00:21

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#constant isn't evaluated as you might expect, it's really a pre-processor. So the text gets injected into source code in place of the constant name.

So this bit of mock up code...

+ Code Snippet

 

#constant Air Create_block("Air",0,1,0,false)


select world(X_loop + top_left_block.X,Y_loop + top_left_block.Y).block
    
     case (Air)
               do whatever here..
      endcase
endselect

become this, after the replacements have been made AIR and other constants.

+ Code Snippet

 

select world(X_loop + top_left_block.X,Y_loop + top_left_block.Y).block
    
     case (Create_block("Air",0,1,0,false))
               do whatever here..
      endcase
endselect

Now even though the expression Create_block("Air",0,1,0,false might appear to be solvable at compile time, DBpro doesn't support this. So the compiler is seeing the Create_block function call returns a dynamic integer result, which is not compatible with the CASE statement, which only supports literal.

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Death_fox

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Joined: 18th Apr 2012

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Posted: 9th Nov 2012 01:19

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thanks for the detail explanation kevin, i'm going to seperate the function from the constant but is there any why to bypass this out of curiosity

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DarkBASIC Professional Discussion / Help with case statement and constants