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Lua Articles
Page 4 of 6
Variable number of arguments in Lua Programming
There are functions in Lua that accept a variable number of arguments. These are very helpful in cases where we want to run the same function with many different arguments that might vary in length. So, instead of creating a different function, we pass them in a variable arguments fashion.Syntaxfunction add(...) -- function code endIt should be noted that the three dots (...) in the parameter list indicate that the function has a variable number of arguments. Whenever this function will be called, all its arguments will be collected in a single table, which the function addresses ...
Read MoreReturn statement in Lua Programming
There are certain cases where we want to return a value from a given function so that we can use it later. These return values make use of a return keyword which in turn allows a function to return values.There is an implicit return at the end of any function, so you do not need to use one if your function ends naturally, without returning any value.It should be noted that the return statement is optional; if not specified, the function returns nil.Also, only one return statement is allowed in a function.Syntaxreturn expression/valueNow let’s consider an example where we would ...
Read MoreNumeric for in Lua Programming
In Lua, there are two types of for loops − the numeric for and the generic for.SyntaxThe numeric for uses the following syntax −for var=exp1, exp2, exp3 do something endIt should be noted that we can write exp1, exp2, exp3 at the same time or we can omit one of them, and the numeric loop will not result in a compile error, though its functionality will change.ExampleLet’s consider a simple variation of a numeric for loop, where we will try to print numbers from 1 to 10.Consider the example shown below −for i = 1, 10 do ...
Read MoreGeneric for in Lua Programming
The generic for in Lua allows us to iterate over the values in an iterator fashion; it is much more powerful even though it looks simple. The Lua library has plenty of iterators, over which we can use the generic for loop.Syntaxfor i, v in pairs(x) do ... ... endThe i in the above syntax denotes the index of the items we are going to iterate over only by one, and the v denotes the actual values of those items. The x is the iterable item over which ...
Read MoreHow to create standalone Lua executables?
We can create standalone Lua executables with the help of the third party packages like srlua.srlua does a perfect job in converting a Lua script file into an executable, and we can do it on both the major platforms, whether that is the windows or the Unix based systems.Let’s first learn how to do it on a Windows system.Consider the steps mentioned below as a reference −First, visit the github link of the srlua project. Please click the following link. After that, you need to clone the repository on your local windows machine with this command −git clone https://github.com/LuaDist/srlua.gitIt should ...
Read MoreHow to convert JSON string into Lua table?
When working with JSON we generally need to decode JSON into a string or maybe encode a string into JSON. Both of these processes of converting the string into a JSON or the opposite are seen frequently.While Lua doesn’t provide an official library to do the same, we can still make use of the third party libraries.There are many third party libraries that we can make use of, out of these the most common one is the json-lua library which can be located on this link.We can either clone the repository on our local machine and then install it or ...
Read MoreHow to compile embedded Lua code in C?
We know that Lua does a great job when it comes to being a simple language and an embedded language. Lua works even better with C, because of the different libraries that provide a great amount of support for it.In order to compile embedded Lua in C, we need to first write a Lua program followed by a C program that will invoke the Lua program function, and then we will compile the C program.Consider the program shown below as the Lua program −print("--I am using Lua from within C--")It should be noted that the above Lua script should be ...
Read MoreHow to Compile a Lua Executable?
While there are different ways with which a person can compile a Lua executable, some of them require more time and resources.The most basic approach is to set the Lua Path environment variable and then simply run the lua command. While this might seem to be not much of a pain, setting the Lua Path definitely requires some work.Instead of setting the Lua path, we can simply make use of the env and lua combination which will allow us to convert a Lua file into an executable or run a Lua script.The command shown below does the same −#!/USR/BIN/ENV LUAIn ...
Read MoreHow to Call a Lua function from C?
Calling a Lua function from C is something that requires a series of steps and a mastery in the Lua library functions. Lua provides several library functions that we can use whenever we want to call Lua functions from C or the opposite.Some of the most commonly used Lua library functions for calling a Lua function from C are −luaL_dofile(L, "myFile.lua");lua_getglobal(L, "add");lua_pushnumber(L, a);and much more.We will make use of these functions when we will call a Lua function from C.The first step is to shut down the Lua interpreter and for that we need to write a code in C.ExampleConsider ...
Read MoreCommand Line arguments in Lua
Handling command line arguments in Lua is one of the key features of any programming language. In Lua, the command line arguments are stored in a table named args and we can use the indices to extract any particular command line argument we require.Syntaxlua [options] [script [args]]The options are −-e stat− executes string stat;-l mod− "requires" mod;-i− enters interactive mode after running script;-v− prints version information;--− stops handling options;-− executes stdin as a file and stops handlingoptions.ExampleLet’s consider an example where we will open a Lua shell in interactive mode and we will pass the script as dev/null and then we ...
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