OpenEuphoria

Re: New switch/case idea

• Posted by DerekParnell (admin) Mar 31, 2009
• 1844 views

Welcome to alpha testing.

Why does ':' obviously mean fall through and '::' obviously mean do not fall through? How is one supposed to remember the difference? In my opinion, it would also be easy to code the wrong thing by accident, even if one did remember which was which. And locating such a bug for the code reader would also be difficult given that ':' and '::' are so similar.

The current syntax makes it explicit and clear what the switch is doing.

The style of Euphoria is based on English words and not punctuation symbols, so it was decided that ':' should be replaced by 'then' as it is similar in style to the if statement, of which switch is a variant of.

switch X do   
  case 1:: -- do code until next case is encountered then break 
     ? 1  
  case 2, 3, 4: -- fall through 
     ? 2  
  case 5: -- fall through 
     ? 5 
  case 30:: -- do code until next case is encountered then break 
     ? 30 
     ? 123 
  case 27:: -- do code until next case is encountered then break 
     ? 27 
  case 81: -- fall through 
     ? 81 
end switch  

The final syntax for this is not finalized, but one suggestion is ...

switch X do  -- by default does NOT fallthru 
  case 1 then 
     ? 1  
  case 2, 3, 4 then 
     ? 2  
     fallthru 
  case 5 then 
     ? 5 
     fallthru 
  case 30 then 
     ? 30 
     ? 123 
  case 27 then 
     ? 27 
  case 81 then 
     ? 81 
end switch  

I think that if you do some analysis you will find that the majority of switch usage is non fall through, so we have made that the default setting and this will mean less typing to do.