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Lua execute function

Lua execute function

Functions are simply a bunch grouped together commands lines of code with the global environment plus a local environment. Since functions are one of the 6 fundamental types, variable naming conventions apply. First comes the "function" keyword, which denotes the next word after a space is the function name. This is one of the things that makes functions different than other variables Having a keyword to denote that it is a function. After the keyword comes a space, and then the function name.

Remember to follow variable naming conventions. After the function name comes an opening parenthesisand then the Argument list.

26 – Calling C from Lua

The Argument list is a series of unique variable names that stand as placeholders for values that can be passed to the function to use to get it's output.

This will be better explained in a second. After the first variable placeholder, each other one is seperated by a comma.

A closing parenthesis denotes the end of an argument list. After the closing parenthesis, you type the function code. The function code can be any series of commands, from one print statement to a huge line complex triginometry math function.

It all depends on what the function is supposed to do.

lua execute function

After the function code, there is the "end" statement, which denotes the end of the function code and also the function. To beter define the argument list, is is simply a list of variable names that, when a function is called, recieve values and then the variable name and value combine into a variable. The variable is then added to the local environment of the function.

If the function caller leaves out an argument when they call the function, the variable's value becomes nil. The nameOfFunction is just the name of the function. The argList is the comma seperated values to pass to the function.

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These can be either variables or literals. If it is a variable, only the value will be passed on, taking on the variable placeholder name in the function.

When calling a function, the values passed must be in the correct order that you envisioned when you created the function. For example, say you have a function called gm that takes two arguments: a string value as the first and a number as the second. If you called gm with a number first and string second, or maybe nil first and a thread second, the function will hopelessly error or give a darasticly incorrect value!Lua provides a mode called interactive mode.

In this mode, you can type in instructions one after the other and get instant results. This can be invoked in the shell by using the lua -i or just the lua command.

Once you type in this, press Enter and the interactive mode will be started as shown below. Invoking the interpreter with a Lua file name parameter begins execution of the file and continues until the script is finished. When the script is finished, the interpreter is no longer active. Let us write a simple Lua program.

Lua - Error Handling

All Lua files will have extension. So put the following source code in a test. The first line is ignored by the interpreter, if it starts with sign. Let us now see the basic structure of Lua program, so that it will be easy for you to understand the basic building blocks of the Lua programming language.

Lua Tutorial 28: Calling C Functions From Lua

A Lua program consists of various tokens and a token is either a keyword, an identifier, a constant, a string literal, or a symbol. Comments are like helping text in your Lua program and they are ignored by the interpreter. A Lua identifier is a name used to identify a variable, function, or any other user-defined item.

Lua is a case sensitive programming language. Thus Manpower and manpower are two different identifiers in Lua. The following list shows few of the reserved words in Lua. These reserved words may not be used as constants or variables or any other identifier names. A line containing only whitespace, possibly with a comment, is known as a blank line, and a Lua interpreter totally ignores it.

Whitespace is the term used in Lua to describe blanks, tabs, newline characters and comments. Whitespace separates one part of a statement from another and enables the interpreter to identify where one element in a statement, such as int ends, and the next element begins.

Calling Lua Functions

There must be at least one whitespace character usually a space between local and age for the interpreter to be able to distinguish them. Lua - Basic Syntax Advertisements. Previous Page. Next Page.

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Live Demo. Previous Page Print Page.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. I need to execute a Lua script from inside another Lua script. How many ways are there, and how do I use them? Notice that you do not use the.

More information here if needed. Learn more. How do I run another script from inside Lua? Ask Question. Asked 7 years, 3 months ago. Active 6 years, 5 months ago. Viewed 21k times. What do you mean by "run" one? Or do you want to execute it from within your script code?

Active Oldest Votes.

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Usually you would use the following: dofile "filename. Example: foo. Just want to add a note for coming readers: require " " must be a script with the extension. MaxKielland are you saying that dofile lets me attach scripts written in different languages? But as you know, you can rename any file to whatever you want. Your Lua script could be named MyGame. But if you use require it MUST have the extension.

All global functions will be accessible as if they were declared in your "main" file.

lua execute function

In this way I can declare local "helper" functions in my library that can't be accessed from the "main" file.This is the second in my series of tutorials covering the Lua scripting language. The first tutorial deals with setting up Lua on Windows and Linux and compiling your first "Hello, World! If you haven't been through the first tutorial yet, please read it now.

This tutorial now covers version 5. There are some pretty major differences in each version of Lua. The code shown below will not work in older versions of Lua. If you are still using an older version and don't want to upgrade, I have provided downloads for version 4.

With that in mind, let's get started.

lua execute function

We will cover passing arguments, returning values, and deal with global variables. Defining functions in Lua is very simple. Start with the word "function", followed by the function name, and a list of arguments.

Function definitions end with the word "end". Functions in Lua can accept multiple arguments and return multiple results. Here's a simple Lua function that adds two numbers and returns their sum.

Save this file as add. As I said earlier, functions in Lua can accept multiple arguments and return multiple results. This is done using a stack. To call a Lua funcion, we first push the function onto the stack. The function is followed by the arguments, in order. After the function call, the return value is available on the stack.

All of these steps are demonstrated in the luaadd function below. Save this file as luaadd.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information.

I was able to store functions into a table. But now I have no idea of how to invoke them. The final table will have about calls, so if possible, I'd like to invoke them as if in a foreach loop. I modified the functions so they'll have a little more context. Basically, they return strings now. And what I was hoping to happen is that at then end of invoking the functions, I'll have a table ideally the levels table containing all these strings.

Short answer: to call a function reference stored in an array, you just add parametersas you'd normally do:.

Long answer: You don't describe what your expected results are, but what you wrote is likely not to do what you expect it to do. Take this fragment:. You actually call these functions and store the values they return they both return nilso when this fragment is executed, you get "table index is nil" error as you are trying to store nil using nil as the index. Using what you guys answered and commented, I was able to come up with the following code as a solution:.

Now, asd contains the area strings I need.

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Although ideally, I intended to be able to access the data like:. It's not really clear what you're trying to do. Same thing for talk. Learn more. Asked 6 years, 10 months ago.

Active 6 years, 6 months ago. Viewed 21k times. It's not clear how or what you want invoked in the loop. Perhaps you can explain and give pseudo-code. BTW—Lua doesn't have pointers.

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Functions are values of type function and can be used anywhere in expressions. TomBlodget, thanks for pointing that out.

lua execute function

I corrected it. Active Oldest Votes. Paul Kulchenko Paul Kulchenko 21k 3 3 gold badges 27 27 silver badges 45 45 bronze badges. Although ideally, I intended to be able to access the data like: asd[1][1] accessing it like: asd["scene0"][1] to retrieve the area data would suffice.A stack is a list of items where items can be added pushed or removed popped that behaves on the last-in-first-out principle, which means that the last item that was added will be the first to be removed.

This is why such lists are called stacks: on a stack, you cannot remove an item without first removing the items that are on top of it.

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All operations therefore happen at the top of the stack. An item is above another if it was added after that item and is below it if it was added before that item.

A function also called a subroutine, a procedure, a routine or a subprogram is a sequence of instructions that perform a specific task and that can be called from elsewhere in the program whenever that sequence of instructions should be executed. Functions can also receive values as input and return an output after potentially manipulating the input or executing a task based on the input.

Functions can be defined from anywhere in a program, including inside other functions, and they can also be called from any part of the program that has access to them: functions, just like numbers and strings, are values and can therefore be stored in variables and have all the properties that are common to variables. These characteristics make functions very useful. Because functions can be called from other functions, the Lua interpreter the program that reads and executes Lua code needs to be able to know what function called the function it is currently executing so that, when the function terminates when there is no more code to executeit can return to execution of the right function.

This is done with a stack called the call stack: each item in the call stack is a function that called the function that is directly above it in the stack, until the last item in the stack, which is the function currently being executed. When a function terminates, the interpreter uses the stack's pop operation to remove the last function in the list, and it then returns to the previous function.

There are two types of functions: built-in functions and user-defined functions. Built-in functions are functions provided with Lua and include functions such as the print function, which you already know. Some can be accessed directly, like the print function, but others need to be accessed through a library, like the math. User-defined functions are functions defined by the user.

User-defined functions are defined using a function constructor:. The code above creates a function with three parameters and stores it in the variable func. The following code does exactly the same as the above code, but uses syntactic sugar for defining the function:. It should be noted that, when using the second form, it is possible to refer to the function from inside itself, which is not possible when using the first form. In both cases, it is possible to omit the local keyword to store the function in a global variable.

Parameters work like variables and allow functions to receive values. When a function is called, arguments may be given to it. The function will then receive them as parameters.

Parameters are like local variables defined at the beginning of a function, and will be assigned in order depending on the order of the arguments as they are given in the function call; if an argument is missing, the parameter will have the value nil.Error handling is quite critical since real-world operations often require the use of complex operations, which includes file operations, database transactions and web service calls. In any programming, there is always a requirement for error handling.

Errors can be of two types which includes. Syntax errors occur due to improper use of various program components like operators and expressions. A simple example for syntax error is shown below. As you know, there is a difference between the use of a single "equal to" and double "equal to".

Using one instead of the other can lead to an error. One "equal to" refers to assignment while a double "equal to" refers to comparison. Similarly, we have expressions and functions having their predefined ways of implementation. Syntax errors are much easier to handle than run time errors since, the Lua interpreter locates the error more clearly than in case of runtime error.

From the above error, we can know easily that adding a do statement before print statement is required as per the Lua structure. In case of runtime errors, the program executes successfully, but it can result in runtime errors due to mistakes in input or mishandled functions. A simple example to show run time error is shown below. When we build the program, it will build successfully and run.

Once it runs, shows a run time error. This is a runtime error, which had occurred due to not passing two variables. The b parameter is expected and here it is nil and produces an error. A simple example is shown below. The error message [, level] terminates the last protected function called and returns message as the error message.

This function error never returns. Usually, error adds some information about the error position at the beginning of the message. The level argument specifies how to get the error position. With level 1 the defaultthe error position is where the error function was called.

Level 2 points the error to where the function that called error was called; and so on. Passing a level 0 avoids the addition of error position information to the message. In Lua programming, in order to avoid throwing these errors and handling errors, we need to use the functions pcall or xpcall. The pcall f, arg1, If some error occurs in function f, it does not throw an error.