IF structure from Hands on Darkbasic pro not working

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Cybermind

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Posted: 23rd Jun 2013 12:38 Edited at: 23rd Jun 2013 12:39

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Hi, I am reading Hands on Darkbasic pro vol. 1 and it tells me I should be able to make an IF structure like this:

+ Code Snippet

variable = 3
if
	variable = 1:
		output = 1
	variable = 2:
		output = 2
	variable = 3:
		output = 3
endif

do
	print output
loop

But the compiler tells me the IF condition only takes one parameter :-( Is it the book that is giving me some bad info or am I doing something wrong here?

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Scotty1973

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Posted: 23rd Jun 2013 12:50

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Hi

Dont know about the if statement but you can use Select statement instead :

+ Code Snippet

var=3
select var

    case 1:
       rem output 1
      
      
     endcase
     
     case 2:
        rem output 2
     
     endcase
        
     case 3:
        rem output 3
     
     endcase
        
endselect

Hope this helps, as it seems to be what you are trying to do.

Scotty

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Cybermind

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Posted: 23rd Jun 2013 13:01 Edited at: 23rd Jun 2013 13:01

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I wanted to create a "catch all" IF structure like this:

+ Code Snippet

variable = 3
if
	variable = 1:
		output = 1
	variable = 2:
		output = 2
	variable = 3:
		output = 3
        else
                output = 4
endif

do
	print output
loop

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Scotty1973

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Posted: 23rd Jun 2013 13:07

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Ok no problems just add a Default case to the statement to catch any other number that isn't selected in the case statements:

+ Code Snippet

var = 1
out=0

select var
    case 1:
        out =1
    endcase
    
    case 2:
        out =2
    endcase
        
    case 3:
        out =3
    endcase
    
    
    case default
        out =4
   
    endcase
    
    
endselect

do
    print out
    
LOOP

This should catch all.

Scotty

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Cybermind

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Posted: 23rd Jun 2013 13:38 Edited at: 23rd Jun 2013 13:46

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Okay, thank you

I just find it odd that there is a useless IF example in the learning book :-( The problem with the select method might be that it only accepts one variable for selecting. Does it only accept integers or can you also use strings and reals??

EDIT: Now the book introduced something else that seems useless:

+ Code Snippet

FOR 3 times DO
  inc total
ENDFOR

print total

Is this something that used to be in DBPRO and have become obsolete??

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TheComet

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Posted: 23rd Jun 2013 13:55

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That's odd...

Should be:

+ Code Snippet

for t = 1 to 3
   inc total
next t

print total

t is a variable which counts from 1 to 3.

TheComet

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Cybermind

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Posted: 23rd Jun 2013 14:14

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I know, I just thought "Yay, I can do a FOR without any variable being used" but I guess not :-(

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Pincho Paxton

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Posted: 23rd Jun 2013 16:53

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Weird mistakes in the book.

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Scotty1973

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Posted: 23rd Jun 2013 17:49

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Yes you can use strings or real numbers in the select statement.

Looking at the stuff your putting in the code box it looks a bit like pseudocode, which is written more like english for people to understand more and won't work on the computer.

Scotty

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Cybermind

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Posted: 24th Jun 2013 10:10

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It tells me that FOR and ENDFOR are commands :-(

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Burning Feet Man

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Posted: 24th Jun 2013 12:42 Edited at: 24th Jun 2013 13:34

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My favourite style of check is this;

+ Code Snippet

`Setup Constants
#Constant Check_1 1
`Setup some Variables
Something_To_Check as Dword
`Assign a value to your variables
Something_To_Check = 1

`Now check! 
IF (Something_To_Check && Check_1)
	Print "Check 1 True"
Else
	Print "Check 1 False"
ENDIF 
wait key
end

Anyone know what this technique is called? Is it a "Bitwise" check?

Oh, almost forgot, expanding on my above example;

+ Code Snippet

`Setup Constants
#Constant Check_1 1
#Constant Check_2 2
#Constant Check_3 4
#Constant Check_4 8

`Setup some Variables
Something_To_Check as Dword
`Assign a value to your variables

Something_To_Check = 3

`Now check! 
IF (Something_To_Check && Check_1)
	Print "Check 1 True"
Else
	Print "Check 1 False"
ENDIF

IF (Something_To_Check && Check_2)
	Print "Check 2 True"
Else
	Print "Check 2 False"
ENDIF 

IF (Something_To_Check && Check_3)
	Print "Check 3 True"
Else
	Print "Check 3 False"
ENDIF 

IF (Something_To_Check && Check_4)
	Print "Check 4 True"
Else
	Print "Check 4 False"
Endif 
 
wait key
end

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Cybermind

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Posted: 29th Jun 2013 15:32

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Quote: "Anyone know what this technique is called? Is it a "Bitwise" check?"

I think that method is called "Binary selection", binary meaning that it can choose between two selections. There are also "Multiway selection" where it can choose between several selections, like SELECT CASE, multiple IF - ENDIF or multiple IF - THEN. I actually don't know if this answers your question

Or if you meant something else with "Bitwise"

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AlistairS

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Posted: 11th Jul 2013 13:55

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@Cybermind

Sorry I've taken time to respond to your post but I have only just noticed it.

The Hands On DBPro book does not claim that DBPro has the structures you refer to. Those structures are used in structured English to describe the algorithm in a way that is independent of the language you finally code in.

If the book does not make that clear, I'm sorry, but no one else has ever mentioned this problem to me.

If you or anyone who has bought the book is in need of help with its contents, please email me. You will find details of the address on our website (www.digital-skills.co.uk).

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basjak

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Posted: 11th Jul 2013 22:15

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you're looking for a multiple way selection. this is mentioned in DBpro book but it says clearly that it is not available in DBpro coding so instead you should use:

variable = 3
if variable = 1
output = 1
else : if variable = 2:
output = 2
else :if variable = 3:
output = 3
endif : endif : endif

do
print output
loop

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MrValentine

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Posted: 11th Jul 2013 23:14

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Quote: "The Hands On DBPro book does not claim that DBPro has the structures you refer to. Those structures are used in structured English to describe the algorithm in a way that is independent of the language you finally code in."

^ This

Quote: " If the book does not make that clear, I'm sorry, but no one else has ever mentioned this problem to me.
"

Pretty sure it makes them very clear in book 1 Page 0 [Before Page 1] and it is titled in huge Bold letters...

Language Syntax Diagrams

Love the books and thank you for them! they are priceless to me! albeit I only have the PDF versions....... hope I can get the printed ones someday...

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Libervurto

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Posted: 12th Jul 2013 06:06 Edited at: 12th Jul 2013 06:09

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@basjak and burningfeetman - SELECT--CASE is made for when you want to execute different code on different values of the same variable.

+ Code Snippet

for n = 1 to 5
  select n
    case 1 : a = 5 : endcase
    case 2 : a = 14 : endcase
    case 3 : a = 88 : endcase
    case default : a = 0 : endcase
  endselect

  print n ; ". " ; a
next n

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Cybermind

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Posted: 13th Jul 2013 21:44

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@AlistairS:

Quote: "Those structures are used in structured English to describe the algorithm in a way that is independent of the language you finally code in."

Sorry, I did not notice that :-P

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Cybermind

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Posted: 15th Jul 2013 18:47

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I did not mean to "bad mouth" the book by the way! I think it is great reading and a good introduction to DBPRO. I am missing some basics as I just learned DBPRO on my own and I think this book does a great job telling the needed to know about getting into DBPRO

Just to clarify

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Dragon slayer

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Posted: 21st Jul 2013 01:53

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That is psoudo code in the book

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MrValentine

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Posted: 21st Jul 2013 02:08

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Quote: "psoudo "

^
pseudo or more accurately Pseudocode

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DarkBASIC Professional Discussion / IF structure from Hands on Darkbasic pro not working