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| .DS_Store |
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| <meta charset="utf-8"> | ||
| <title>Lua</title> | ||
| <style>@import url(style.css);</style> | ||
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| <h1>Lua, the Programming Language</h1> | ||
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| <style> | ||
| .moon { | ||
| font-size: 400%; | ||
| transform: rotate(10deg) translate(50px, 50px); | ||
| } | ||
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| lua-word { | ||
| font-weight: bold; | ||
| font-family: monospace; | ||
| } | ||
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| </style> | ||
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| <div class="moon">☽</div> | ||
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| <p> | ||
| Have you noticed the moon is a bit like a parenthesis? | ||
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| <p> | ||
| Things of amazing beauty were invented by humans: first it was Lisp, then it | ||
| was Forth, and then it was Lua - if there were other good languages, please | ||
| let me know | ||
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| <p align="center"> | ||
| <table> | ||
| <thead> | ||
| <tr> | ||
| <th>Language</th> | ||
| <th>Year of Release</th> | ||
| <th>Keywords</th> | ||
| </tr> | ||
| </thead> | ||
| <tbody> | ||
| <tr> | ||
| <td>Lisp</td> | ||
| <td>1960</td> | ||
| <td>defun, cons, car, cdr, lambda, eval, cond</td> | ||
| </tr> | ||
| <tr> | ||
| <td>Forth</td> | ||
| <td>1970</td> | ||
| <td>:, dup, drop, pick, roll</td> | ||
| </tr> | ||
| <tr> | ||
| <td>Smalltalk</td> | ||
| <td>1972</td> | ||
| <td>new, yourself, super</td> | ||
| </tr> | ||
| <tr> | ||
| <td>Scheme</td> | ||
| <td>1975</td> | ||
| <td>define, call/cc, set!, define-syntax</td> | ||
| </tr> | ||
| <tr> | ||
| <td>Common Lisp</td> | ||
| <td>1984</td> | ||
| <td>defun, defmacro, defparameter, defclass, defpackage, loop</td> | ||
| </tr> | ||
| <tr> | ||
| <td>Python</td> | ||
| <td>1991</td> | ||
| <td>def, class, nonlocal, async, yield, import</td> | ||
| </tr> | ||
| <tr style="background: pink"> | ||
| <td>Lua</td> | ||
| <td>1993</td> | ||
| <td>function, local</td> | ||
| </tr> | ||
| </tbody> | ||
| </table> | ||
| <em>Table 1. Various languages.</em> | ||
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| <p> | ||
| The good thing about being a 1993 language is that you can be influenced by every other language that was released before that date. In Lua, I personally sense a great influence of every language mentioned in <em>Table 1</em>, and I like these influences | ||
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| <p> | ||
| conf: __index, __add, __le, __mode -- __init__, __str__, __add__ | ||
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| <p> | ||
| conf: _G -- globals() | ||
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| <p> | ||
| They say there's a man in the moon - if you look closely enough into moon's | ||
| surface, you will see a face. In case of Lua, the face you see in the moon | ||
| is of <strong><a href="https://en.wikipedia.org/wiki/Roberto_Ierusalimschy">Roberto Ierusalimski</a></strong> [Wikipedia]. When I say this, I always want to add "it's the | ||
| same guy who made D" but D was made by <a href="https://en.wikipedia.org/wiki/Andrei_Alexandrescu">Andrei Aleksandresku</a> [Wikipedia], an entirely | ||
| different person<sup><a href="#note1">1</a></sup> | ||
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| <p class="slide" id="note1"> | ||
| <sup>1</sup> No wonder I keep getting them confused, their last names both end with /sk[ui]$/ | ||
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| <p> | ||
| One thing that comes to mind first when thinking about Lua is that it begins | ||
| indexing its arrays (aka tables) with 1 as opposed to 0, the starting index | ||
| of choice of 99% other programming languages. Both are nice choices, one is | ||
| more intuitive when thinking about high-level problems, the other is more | ||
| intuitive when dealing with things like memory or anything with an "offset". | ||
| A truly bad choice would be using -1 or 2 as base index | ||
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| <p> | ||
| The reason behind this is that Lua was indeed designed to be used by | ||
| non-programmers, who needed a very simple language to automate their daily | ||
| computations. It's a small niche, and we don't usually target it anymore when | ||
| developing software. We kind of collectively assume that programming is the | ||
| job of a programmer, and now that we have a lot of programmers, why would | ||
| <em>you</em> code instead of them? | ||
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| <p> | ||
| Another instance of this is that every assignment to a free variable introduces | ||
| a global binding, visible across all modules. If you're a novice programmer, | ||
| this is a win for you because you don't have to wonder why your variable | ||
| suddenly became <lua-word>nil</lua-word>, and if you're an experienced | ||
| developer, you probably care about lexical scoping and should by default make | ||
| every variable you use with <lua-word>local</lua-word>. You also need to be | ||
| careful not to assign to undeclared variables, but your <abbr title="Integrated Development Environment">IDE</abbr> | ||
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| <p> | ||
| Metatables are the continuation of theme "we're giving you one multi-purpose | ||
| tool instead of many single-purpose utilities" that table has begun. Metatables | ||
| are your meta-programming tool, and with meta-programming you may achieve object | ||
| oriented programming (OOP) and other good stuff. Lua doesn't have macros, but | ||
| metatables make it possible to introduce custom syntax to a degree. Personally | ||
| I recommend against going for the urge of rolling out Your Own Object System | ||
| because it's not a natural style for Lua: whatever you need an object system | ||
| for (inheritance, overriding behavior, polymorphism), there are other, more | ||
| straightforward ways to implement these. Lua isn't very like Smalltalk, it's | ||
| almost trying to be the opposite of Smalltalk while pursuing similar goals in | ||
| its design |
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