OpenEuphoria

Re: New Switch Idea

• Posted by DerekParnell (admin) Mar 27, 2009
• 1113 views

I think that the syntax needs to be ...

switch <expr> [(with | without fallthru)] [label "name"] [do] 
   case <valuelist> [:] 
      <statements> 
   case <valuelist> [:] 
      <statements> 
   case <valuelist> [:] 
      <statements> 
   . . . 
   case else 
      <statements> 
end switch 

Where

• <expr> is an expression that evaluates to any Euphoria object
• If there is no 'fallthru' clause then 'without fallthru' is assumed
• <valuelist> is a comma-separated list of one or more discrete values that <expr> can equal to.
• <statements> is a block of one or more euphoria statements. A zero length statement block is not allowed.
• If 'without fallthru' is in operation, once <statements> block is executed, control passes to the 'end switch' line. Any 'break' statements are ignored.
• If 'with fallthru' is in operation, once a <statements> block is executed and is does not end in a 'break' statement, control passes to the next (if any) lexical <statements> block, otherwise control is passed to the 'end switch'.
• 'goto' can be used to manually change control flow within a switch.

Examples:

integer X = 1  
switch X without fallthru 
  case 1 
    ? 1  
  case 2  
    ? 2  
end switch  
  
-- output: 
-- 1  

integer X = 1  
switch X with fallthru 
  case 1 
    ? 1  
  case 2  
    ? 2  
end switch  
  
-- output: 
-- 1 
-- 2  

integer X = 1  
switch X with fallthru 
  case 1 
    ? 1  
  case 2  
    ? 2  
    break 
  case 3 
    ? 3 
end switch  
  
-- output: 
-- 1 
-- 2  

integer X = 1  
switch X 
  case 1  
    ? 1  
  case 2  
    ? 2  
end switch  
  
-- output: 
-- 1 

object X = "three" 
switch X  
  case 1,2,"three",4.112233, 5 
    ? 1  
  case 6,7,8,9,10 
    ? 2  
end switch  
  
-- output: 
-- 1