Comment by 201984

20 hours ago

Lua basically already has ternary operators anyway since "and" and "or" short circuit. I also don't see the need of adding additional syntax for it.

  local x = condition ? value_a : value b
  local x = condition and value_a or value_b

3 comments

201984

matheusmoreira 20 hours ago

> The classic Lua idiom a and b or c has a pitfall when b is nil or false: then c is returned, even when a is truthy.

> E.g. true and false or 42 returns 42, whereas true ? false : 42 returns the (expected) false.

nmz 4 hours ago

No, not basically, it simply doesn't have them, Ternary means three as in it operates on 3 operands, and/or operates on 2 operands. They are also not equivalent.

   x = a ? b : c # x is b, same as you would if a {x=b} else {x=c}

lua and/or

    a,b,c = true, 1, 2
    x = a and b or c -- x is b


    a,b,c = true, false, 2
    x = a and b or c -- x is c

The or is dependent on its previous operand, so b will return false and skips to c, even if you meant for it to be b. you must use an if then else. However, you can have more than a ternary, if there is no need for short-circuit evaluation, as in, any of the operand is not a function CALL like c(), and you want to remain inside an expression, then you can do this instead

select (select is a native C function, this is faster than the table creation below)

    x = select(a and 1 or 2, b, c)

table creation/selection

    x = ({false,2})[a and 1 or 2]

of course, doing something like

   local x; if a then x=b else x=c end

does not look so bad