coroutine.status (co) Returns the status of coroutine co, as a string: "running", if the coroutine is running (that is, it called status); "suspended", if the coroutine is suspended in a call to yield, or if it has not started running yet; "normal" if the coroutine is active but not running (that is, it has resumed another coroutine); and "dead" if the coroutine has finished its body function, or if it has stopped with an error.

coroutine.running () Returns the running coroutine plus a boolean, true when the running coroutine is the main one.

coroutine.resume (co [, val1, ···]) Starts or continues the execution of coroutine co. The first time you resume a coroutine, it starts running its body. The values val1, ... are passed as the arguments to the body function. If the coroutine has yielded, resume restarts it; the values val1, ... are passed as the results from the yield. If the coroutine runs without any errors, resume returns true plus any values passed to yield (when the coroutine yields) or any values returned by the body

coroutine.isyieldable () Returns true when the running coroutine can yield. A running coroutine is yieldable if it is not the main thread and it is not inside a non-yieldable C function.

coroutine.create (f) Creates a new coroutine, with body f. f must be a function. Returns this new coroutine, an object with type "thread".

3.3.4 – Control Structures The control structures if, while, and repeat have the usual meaning and familiar syntax: stat ::= while exp do block end stat ::= repeat block until exp stat ::= if exp then block {elseif exp then block} [else block] end Lua also has a for statement, in two flavors (see §3.3.5). The condition expression of a control structure can return any value. Both false and nil are considered false. All values different from nil and false are considered true (in particular,

3.4.6 – Concatenation The string concatenation operator in Lua is denoted by two dots ('..'). If both operands are strings or numbers, then they are converted to strings according to the rules described in §3.4.3. Otherwise, the __concat metamethod is called (see §2.4).

collectgarbage ([opt [, arg]]) This function is a generic interface to the garbage collector. It performs different functions according to its first argument, opt: "collect": performs a full garbage-collection cycle. This is the default option. "stop": stops automatic execution of the garbage collector. The collector will run only when explicitly invoked, until a call to restart it. "restart": restarts automatic execution of the garbage collector. "count": returns the total memory

3.4.3 – Coercions and Conversions Lua provides some automatic conversions between some types and representations at run time. Bitwise operators always convert float operands to integers. Exponentiation and float division always convert integer operands to floats. All other arithmetic operations applied to mixed numbers (integers and floats) convert the integer operand to a float; this is called the usual rule. The C API also converts both integers to floats and floats to integers, as needed. M

3.3.2 – Chunks The unit of compilation of Lua is called a chunk. Syntactically, a chunk is simply a block: chunk ::= block Lua handles a chunk as the body of an anonymous function with a variable number of arguments (see §3.4.11). As such, chunks can define local variables, receive arguments, and return values. Moreover, such anonymous function is compiled as in the scope of an external local variable called _ENV (see §2.2). The resulting function always has _ENV as its only upvalue, even if