Editing RPL (programming language) (section)

====CASE/THEN/END====
To support more complex conditional logic, RPL provides the CASE/THEN/END structure for handling multiple exclusive tests. Only one of the branches within the CASE statement will be executed. The basic syntax of this block is:

  CASE 
   condition_1 THEN if-condition_1 END 
    ...
   condition_n THEN if-condition_n END
   if-none
  END

The following code illustrates the use of a CASE/THEN/END block. Given a letter at the bottom of the stack, it replaces it with its string equivalent or "Unknown letter":

  « 
    CASE 
       DUP "A" == THEN "Alpha" END
       DUP "B" == THEN "Beta" END
       DUP "G" == THEN "Gamma" END
       "Unknown letter"
    END
    SWAP DROP  @ Get rid of the original letter
  »

This code is identical to the following nested IF/THEN/ELSE/END block equivalent:

  «
     IF DUP "A" ==
     THEN
        "Alpha"
     ELSE 
        IF DUP "B" == THEN
           "Beta"
        ELSE 
           IF DUP "G" == THEN
              "Gamma"
           ELSE
              "Unknown letter"
           END
        END 
     END
     SWAP DROP  @ Get rid of the original letter
  »