Function isyieldable 

pub fn isyieldable() -> boolean

Returns true when the running coroutine can yield — that is, when it is not the main coroutine and it is not inside a non-yieldable C function.

Examples

print(coroutine.isyieldable())    --> false   (main coroutine)
coroutine.wrap(function()
  print(coroutine.isyieldable())  --> true
end)()