Quaternary Operator

[Nilson <nilson.brazil@...>]

Hi all,

As today seems to be the day to talk about Lua's syntax enhancements,
I would like to talk about another one:

"Quaternary operator"

[ <exp>; true_result; false_result; nil_result ]

meaning

function quaternary (cond,true_result,false_result,nil_result)
 if cond then return true_result end
 if not exists(false_result) then return end
 if cond === false then return false_result end
 if exists(nil_result) then
   return nil_result
 else
  return false_result
 end
end

exists is a compile time function

example

  a = b + [c;100;200] + [d;10;20] + [e;1;2;3]
  b = 1000 c = true d = false
  print(a)
  >>> 1123

Another option is allow the use of comma as separator.

PROs:
- No need of a new lexical symbol like '?'
- Optional handle of nil values
- The square brackets naturally eliminate priority problems.

Cons:
- quite different from C

--
Nilson

-- 
Nilson