UserGuide - Decisions & Conditions

There are different ways of processing data obtained from user input or other way (loading from a file, ...). The common arithmetic functions (+, -, *, /, ...) can be combined with conditions. You can use the If : Else/ElseIf : EndIf set of keywords or the Select : Case/Default : EndSelect keywords, just use what is the best for your situation!

This example shows the use of If : ElseIf : Else : EndIf for creating a message, possibly for showing in the status bar of a form (GUI) or something similar, based upon the number of items and filtered items in an, imaginary, list. Note that unlike some other BASIC languages, PureBasic doesn't use the "Then" keyword and that there is no space in the ElseIf and EndIf keywords. 
  Define.l Items = 10, Filter = 6
  Define.s Message
  
  If Items = 0 
    Message = "List is empty."
    
  ElseIf Items = 1 And Filter = 0
    Message = "One item. Not shown by filter."
    
  ElseIf Items > 1 And Filter = 0
    Message = StrU(Items) + " items. All filtered."
    
  ElseIf Items > 1 And Filter = 1
    Message = StrU(Items) + " items. One shown by filter."
    
  ElseIf Items = Filter
    Message = StrU(Items) + " items. None filtered."
    
  Else
    ; None of the other conditions were met.
    Message = StrU(Items) + " items. " + StrU(Filter) +" shown by filter."
    
  EndIf
  
  Debug Message

This example shows the use of Select : Case : Default : EndSelect to categorize the first 127 ASCII characters into groups. The "For : Next" loop counts to 130 to demonstrate the Default keyword. 
  Define.c Char
  Define.s Message
  
  For Char = 0 To 130
    
    Select Char

      Case 0 To 8, 10 To 31, 127
        Message = StrU(Char) + " is a non-printing control code."
        
      Case 9
        Message = StrU(Char) + " is a tab."
        
      Case 32
        Message = StrU(Char) + " is a space."
        
      Case 36, 128   
        Message = StrU(Char) + " is a currency symbol. (" + Chr(Char) + ")"
        
      Case 33 To 35, 37 To 47, 58 To 64, 91 To 96
        Message = StrU(Char) + " is a punctuation mark or math symbol. (" + Chr(Char) + ")"
        
      Case 48 To 57
        Message = StrU(Char) + " is a numeral. (" + Chr(Char) + ")"
        
      Case 65 To 90
        Message = StrU(Char) + " is an upper case letter. (" + Chr(Char) + ")"
        
      Case 97 To 122
        Message = StrU(Char) + " is a lower case letter. (" + Chr(Char) + ")"
        
      Default
        ; If none of the preceding Case conditions are met.
        Message = "Sorry, I don't know what " + StrU(Char) + " is!"
        
    EndSelect
    
    Debug Message
    
  Next Char

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