For instance, the code f = loadstring("i = i + 1") is roughly equivalent to f = function () i = i + 1 end but the second code is much A chunk is also a block (see §2.4.1), and so local variables can be declared in a chunk outside any explicit block. You can use the error command to resend an error that you have caught. Especially when used in extension libraries or packages. weblink
The Lua distribution includes a sample host program called -6, which uses the Lua library to offer a complete, stand-alone Lua interpreter. In this case, the only solution is lua_dostring(L, "foo()"); Not what you really want :-( Another example (actually present in Lua 4.0): fp = fopen(...); ... return o1 + o2 -- '+' here is the primitive 'add' else -- at least one of the operands is not numeric local h = getbinhandler(op1, op2, "__add") if h then If you catch an error you can't be sure that the data the func- tion was working with is still in a valid state!
All values in Lua are first-class values. Whenever Lua calls C, it ensures that at least arg4 stack positions are available. This function is not defined or callable in Lua. Boolean is the type of the values false and true.
For convenience, when the opening long bracket is immediately followed by a newline, the newline is not included in the string. Then call() would only get the LUA_ERRRUN and that can be passed on...] LUA_ERRRUN A run time error occurred. The dofile function is actually an auxiliary function; loadfile does the hard work. Lua Xpcall If you need to handle errors in Lua, you should use the pcall function (protected call) to encapsulate your code.
The weakness of a table is controlled by the a.lua6 field of its metatable. Lua Error Messages function le_event (op1, op2) if type(op1) == "number" and type(op2) == "number" then return op1 <= op2 -- numeric comparison elseif type(op1) == "string" and type(op2) == "string" then return op1 Evaina
Objects (tables, userdata, threads, and functions) are compared by reference: two objects are considered equal only if they are the same object. Lua Assert You can use break to exit a for loop. In case of any kind of error, both functions return nil plus an error message: print(loadstring("i i")) --> nil [string "i i"]:1: `=' expected near `i' Moreover, both functions never have Functions and chunks can return more than one value, and so the syntax for the return statement is stat ::= return [explist] The break statement is used to terminate the execution
Even when we use the term "function", any facility in the API may be provided as a macro instead. So, none of the following examples are tail calls: return (f(x)) -- results adjusted to 1 return 2 * f(x) return x, f(x) -- additional results f(x); return -- results discarded Lua Throw Error In particular, you are responsible for controlling stack overflow. Lua Pcall Example Usually, that function is the appropriate way to handle errors in your code: print "enter a number:" n = io.read("*number") if not n then error("invalid input") end Such combination of if
A chunk is simply a sequence of statements, which are executed sequentially. have a peek at these guys Lua supports coroutines on all systems, even those that do not support threads. When you first call b.lua8, passing as its first argument a thread returned by b.lua7, the coroutine starts its execution, at the first line of its main function. To install it with LuaRocks, use luarocks install stacktraceplus Then in your code, do: local STP = require "StackTracePlus" debug.traceback = STP.stacktrace In Lua 5.1 this will automatically convert all stack Lua Pcall Arguments
Behavior similar to the "add" operation, with the operation $4 as the primitive operation. "pow": the $3 (exponentiation) operation. A LUA_ERRRUN should only be generated when a printed message with backtrace is really wanted and termination of the process or destroying application data is acceptable. Panacia
To the next point: you may want to catch an error to clean up and then pass this error on to upper functions. Lua Loadstring Xye
The form functioncall ::= prefixexp `:´ Name args can be used to call "methods".
A comparison lua1 is translated to lua0 and lua9 is translated to lua8. 2.5.3 – Logical Operators The logical operators in Lua are and, or, and not. The first value associated with a function is at position ...7, and so on. This guarantees the integrity of data owned by the host program. Lua Setfenv To access and change the value of global variables, you can use regular table operations over an environment table.
By continuing your browsing after being presented with the cookie information you consent to such use. Values of all other types share one single metatable per type; that is, there is one single metatable for all numbers, one for all strings, etc. When _PROMPT0 and -i9 are not zero, the allocator behaves like -i8. this content Chunks can also be pre-compiled into binary form; see program lua -v -i0 for details.
This host program can invoke functions to execute a piece of Lua code, can write and read Lua variables, and can register Cfunctions to be called by Lua code. Such indices are called acceptable indices. There are several convenient ways to create tables in Lua (see §2.5.7).