Quaternary Operator
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- Subject: Quaternary Operator
- From: Nilson <nilson.brazil@...>
- Date: 2010年11月20日 12:29:35 -0200
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