Scribunto

1. Scribunto: A Beginner's Guide

Introduction

Scribunto is a powerful scripting language engine for MediaWiki, enabling developers to write dynamic content and complex logic within wiki pages. It transforms wiki pages from static collections of text and images into interactive, data-driven environments. Unlike traditional wiki markup, which is primarily focused on presentation, Scribunto allows for *computation* within the wiki. This opens a vast array of possibilities, from creating advanced templates and data tables to implementing sophisticated tools for data analysis and visualization. This article provides a comprehensive introduction to Scribunto for beginners, covering its core concepts, benefits, usage, limitations, and potential applications.

Why Scribunto? The Need for a Scripting Engine

Historically, MediaWiki’s template system, while flexible, had significant limitations. Complex logic required convoluted template structures, leading to difficult-to-maintain and often slow-performing pages. These limitations stemmed from the fact that templates were primarily designed for text substitution, not for performing calculations, iterating through data, or making conditional decisions based on complex criteria.

Scribunto addresses these limitations by providing a full-fledged scripting environment within MediaWiki. Before Scribunto, developers often resorted to using extensions to introduce scripting capabilities, which could create compatibility issues and increase server load. Scribunto, being a core feature since MediaWiki 1.19, offers a standardized and efficient solution.

The Language: Lua

Scribunto utilizes the Lua programming language. Lua is a lightweight, embeddable scripting language known for its simplicity, efficiency, and portability. It was specifically designed to be integrated into larger applications, making it an ideal choice for MediaWiki.

Why Lua? Several key characteristics make Lua suitable for Scribunto:

• **Simplicity:** Lua has a relatively small core syntax, making it easier to learn than many other programming languages.
• **Efficiency:** Lua is known for its fast execution speed, crucial for maintaining wiki performance.
• **Embeddability:** Lua is designed to be easily integrated into C/C++ applications, seamlessly fitting into MediaWiki's architecture.
• **Sandboxing:** Lua's security features allow Scribunto to run scripts in a sandboxed environment, preventing malicious code from accessing sensitive server resources. This is a critical aspect of maintaining wiki security.
• **Table-centric:** Lua's primary data structure is the table, which can act as an array, dictionary, or object, providing flexibility for handling diverse data types.

Learning Lua is therefore essential to effectively using Scribunto. Numerous online resources are available for learning Lua, including the official Lua website and interactive tutorials.

Core Concepts of Scribunto

Understanding these core concepts is crucial for writing Scribunto code:

• **Modules:** Scribunto code is organized into *modules*. A module is a dedicated wiki page (usually with a `.lua` extension) that contains Lua code. These modules can be called from other templates, modules, or even directly from wiki pages. For example, a module named "Module:MyModule" would be created as a wiki page titled "Module:MyModule".
• **Functions:** Modules define *functions* that perform specific tasks. These functions can accept arguments and return values. Think of functions as reusable blocks of code.
• **Frames:** When a module is called, it receives a *frame* object. The frame represents the context in which the module is being called, including the arguments passed to it and access to the wiki environment. Understanding frames is critical for interacting with templates and accessing wiki data.
• **Return Values:** Functions can return values, which can be used by the calling template or module. Return values can be simple data types (numbers, strings, booleans) or more complex structures like tables.
• **Parameters:** Modules receive input through *parameters* passed from the calling template. These parameters are accessible within the module's frame object.
• **mw Namespace:** Scribunto provides access to a special namespace called `mw`, which contains functions for interacting with the MediaWiki environment. This allows you to retrieve page content, access wiki settings, and perform other wiki-specific tasks. Functions within the `mw` namespace are your bridge between Lua code and the wiki's functionality.

Basic Scribunto Syntax and Examples

Let’s illustrate these concepts with a simple example. Consider a module named "Module:SimpleMath" with the following Lua code:

```lua local p = {} -- Create a table to hold our functions

function p.add(frame)

 local a = tonumber(frame.args[1])
 local b = tonumber(frame.args[2])

 if a == nil or b == nil then
   return "Error: Both arguments must be numbers."
 end

 return a + b

end

return p ```

This module defines a single function called `add`. Here’s a breakdown:

• `local p = {}`: Creates an empty table named `p`. This table will contain the module's functions.
• `function p.add(frame)`: Defines a function named `add` within the `p` table. The `frame` argument represents the frame object.
• `local a = tonumber(frame.args[1])`: Retrieves the first argument passed to the module from the frame's `args` table and converts it to a number using `tonumber()`.
• `local b = tonumber(frame.args[2])`: Retrieves the second argument and converts it to a number.
• `if a == nil or b == nil then`: Checks if either argument is missing or invalid.
• `return "Error: Both arguments must be numbers."`: Returns an error message if either argument is invalid.
• `return a + b`: Returns the sum of the two numbers.
• `return p`: Returns the `p` table, which contains the module’s functions.

To use this module in a template, you would create a template like this:

```wiki {{#invoke:SimpleMath|add|5|3}} ```

This would output `8`.

Interacting with Wiki Data using `mw` Namespace

The `mw` namespace provides access to a wide range of MediaWiki functions. Here are some commonly used functions:

• `mw.title.new(title)`: Creates a title object representing a wiki page.
• `mw.title.get(title)`: Retrieves the page object for a given title.
• `mw.text.extract(text, start, end)`: Extracts a portion of a string.
• `mw.text.match(text, pattern)`: Matches a pattern in a string.
• `mw.parser.extension.tag(frame, tag, args)`: Allows you to call other parser functions from Scribunto.
• `mw.lang.formatDate(date, format)`: Formats a date string according to a specified format.
• `mw.ustring`: Provides string manipulation functions.

Example: Retrieving the content of a page:

```lua local p = {}

function p.getPageContent(frame)

 local pageTitle = frame.args[1]
 local title = mw.title.new(pageTitle)
 if title then
   local page = title.get()
   if page then
     return page.text
   else
     return "Page not found."
   end
 else
   return "Invalid page title."
 end

end

return p ```

You could then use this module in a template like this:

```wiki {{#invoke:GetPageContent|getPageContent|Help:Contents}} ```

This would output the content of the "Help:Contents" page.

Error Handling and Debugging

Scribunto provides error handling mechanisms to help you identify and fix problems in your code.

• **Error Messages:** Scribunto will display error messages on the wiki page if your code contains errors. These messages can provide valuable clues about the source of the problem.
• **`mw.log()`:** Use `mw.log()` to write messages to the MediaWiki error log. This is useful for debugging complex issues. The log is accessible to administrators.
• **`mw.debug()`:** Similar to `mw.log()`, but designed for more detailed debugging information.
• **Sandbox Testing:** Always test your code in a sandbox environment before deploying it to a live wiki. This helps prevent errors from disrupting the wiki’s functionality.

Security Considerations

Scribunto operates in a sandboxed environment to protect the wiki from malicious code. However, it’s still important to be aware of security considerations:

• **Input Validation:** Always validate user input to prevent injection attacks. Sanitize any data received from templates before using it in your code.
• **Resource Limits:** Be mindful of resource limits. Avoid creating infinite loops or consuming excessive memory.
• **Restricted Functions:** Some functions in the `mw` namespace are restricted to prevent security vulnerabilities.

Advanced Techniques and Applications

Scribunto can be used for a wide range of advanced applications:

• **Data Tables and Charts:** Create dynamic data tables and charts that update automatically based on data sources. Consider using libraries for chart generation.
• **Form Generation:** Generate complex forms with validation and data processing capabilities.
• **Data Analysis and Visualization:** Perform data analysis and create visualizations directly within the wiki. This is particularly useful for technical analysis of financial data, including calculating moving averages, Relative Strength Index (RSI), and MACD.
• **Game Development:** Create simple games and interactive experiences.
• **Custom Search Engines:** Implement custom search engines with advanced filtering and sorting options.
• **Automated Reporting:** Generate automated reports based on wiki data.
• **Financial Modeling:** Build models for stock market trends, forex trading strategies, and option pricing.
• **Trading Signal Generation:** Developing algorithms for identifying breakout patterns, reversal indicators, and momentum trading.
• **Risk Management Tools:** Tools for portfolio diversification, volatility analysis, and drawdown calculation.
• **Backtesting Frameworks:** Frameworks for evaluating the performance of algorithmic trading strategies using historical data.
• **Sentiment Analysis:** Integrating APIs for social media sentiment analysis to gauge market mood.
• **Economic Calendar Integration:** Displaying real-time economic data and fundamental analysis indicators.
• **Correlation Analysis:** Identifying relationships between different assets using correlation coefficients.
• **Time Series Analysis:** Predicting future values based on historical data using ARIMA models or Exponential Smoothing.
• **Pattern Recognition:** Identifying chart patterns like head and shoulders, double tops, and triangles.
• **Arbitrage Detection:** Algorithms for identifying price discrepancies across different exchanges.
• **Monte Carlo Simulations:** Running simulations to assess the probability of different outcomes.
• **Machine Learning Integration:** Integrating with machine learning APIs for predictive modeling.
• **Algorithmic Trading Bots:** (With appropriate security measures and restrictions) Developing and deploying automated trading bots.

Resources and Further Learning

• **Official Scribunto Documentation:** Scribunto Documentation
• **Lua Documentation:** Lua Documentation
• **MediaWiki Help Pages:** Help:Lua
• **Scribunto Sandbox:** Use a sandbox wiki to experiment with Scribunto code.
• **Lua Libraries:** Explore available Lua libraries for various tasks.
• **Community Forums:** Participate in the MediaWiki and Scribunto communities to ask questions and share knowledge. MediaWiki talk pages are a good starting point.

Limitations

While powerful, Scribunto has limitations:

• **Execution Time Limits:** Scripts have execution time limits to prevent server overload.
• **Memory Limits:** Scripts have memory limits.
• **Network Access:** Direct network access from Scribunto is restricted for security reasons.
• **Sandboxing:** While beneficial for security, sandboxing can limit access to certain system resources.

Help:Contents Help:Templates Help:Modules Extension:Lua Template:Infobox MediaWiki Lua Help:Editing Help:Formatting Special:AllPages

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