Lua: Difference between revisions

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{{Software

|name = Lua

|image = Lua-Logo.svg.png

|type = Library

|authors = Roberto Ierusalimschy

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}}

Lua (/ˈluːə/ LOO-ə; from Portuguese: lua [ˈlu(w)ɐ] meaning moon) is a lightweight, high-level, multi-paradigm programming language designed mainly for embedded use in applications.[ Lua is cross-platform software, since the interpreter of compiled bytecode is written in ANSI C,and Lua has a relatively simple C application programming interface (API) to embed it into applications.

"During the slow month of December, programmer Sam Lantinga finished making our user interface customizable via a lightweight programming language called Lua. Despite the fact Sam had explained it to the artists a number of times, the concept of a user-controlled interface didn’t make sense, but the designers and programmers assured us it would be great. Most of us couldn’t understand what was so wrong with the default interface that we now wanted to turn control of it over to the general public. Why let users control the interface? How much better could they make it? Wasn’t it clean enough?"

— John Staats, ''The WoW Diary''

</blockquote>

Lua (/ˈluːə/ ''LOO-ə''; from Portuguese: ''lua'' [ˈlu(w)ɐ] meaning moon) is a lightweight, high-level, multi-paradigm programming language designed mainly for embedded use in applications.[ Lua is cross-platform software, since the interpreter of compiled bytecode is written in ANSI C,and Lua has a relatively simple C application programming interface (API) to embed it into applications.

Lua originated in 1993 as a language for extending software applications to meet the increasing demand for customization at the time. It provided the basic facilities of most procedural programming languages, but more complicated or domain-specific features were not included; rather, it included mechanisms for extending the language, allowing programmers to implement such features. As Lua was intended to be a general embeddable extension language, the designers of Lua focused on improving its speed, portability, extensibility and ease-of-use in development.

== WoW Lua ==

By the release of 3.3.5a, Blizzard had made various helpful modifications to its version of Lua.

=== Taint ===

In WoW Lua, each variable contains a taint value, a string that identifies the AddOn from where the variable originated.

=== Profiling ===

Because each variable is taint-tagged by whichever AddOn generated it, WoW Lua is able to compute the memory usage of any particular AddOn.

<pre>

void lua_gcupdatesizes(lua_State* L);

lu_mem lua_gcgetsize(lua_State* L, const char* tag);

</pre>

Optionally, function performance can be profiled by turning on a flag (which is governed by the <code>scriptProfile</code> CVar).

You can read the results of the function profiler with:

<pre>

void lua_gcupdatetimes(lua_State* L);

lua_Number lua_gcgettime(lua_State* L, const char* tag);

void lua_gcgetfunctiontime(lua_State* L, lua_Number* flat, lua_Number* total, int32_t* ncalls);

void lua_gcresettimes(lua_State* L);

</pre>

=== Standard library ===

WoW Lua modifies the standard library by removing functions that expose the host filesystem, modifying existing functions, or adding new ones.

These functions were removed from the standard library:

* <code>dofile()</code>, <code>loadfile()</code> - Removed to prevent Lua from touching the host filesystem.

* <code>load()</code> - Reason for removal unclear

* <code>print()</code> - Removed to prevent Lua from touching stdout. This is replaced by a function that prints output to the ingame chat.

* <code>math.randomseed()</code>

* <code>string.sub()</code>

These existing standard library functions were modified:

* <code>getfenv()</code> - Implementation adds this code to end of function: <code>luaL_getmetafield(L, -1, "__environment");</code>

* <code>string.upper()</code>, <code>string.lower()</code> - These were modified to support UTF-8 strings. Unlike stock Lua, they are able to convert special characters including Latin-1 and Cyrillic.

These standard library functions were added by Blizzard:

* <code>table.removemulti()</code>

* <code>table.wipe()</code>

@@ Line 2: / Line 2: @@
 {{Software
   |name        = Lua
+ |image       = Lua-Logo.svg.png
   |type        = Library
   |authors     = Roberto Ierusalimschy
@@ Line 8: / Line 9: @@
 }}
-Lua (/ˈluːə/ LOO-ə; from Portuguese: lua [ˈlu(w)ɐ] meaning moon) is a lightweight, high-level, multi-paradigm programming language designed mainly for embedded use in applications.[ Lua is cross-platform software, since the interpreter of compiled bytecode is written in ANSI C,and Lua has a relatively simple C application programming interface (API) to embed it into applications.
+<blockquote>
+"During the slow month of December, programmer Sam Lantinga finished making our user interface customizable via a lightweight programming language called Lua. Despite the fact Sam had explained it to the artists a number of times, the concept of a user-controlled interface didn’t make sense, but the designers and programmers assured us it would be great. Most of us couldn’t understand what was so wrong with the default interface that we now wanted to turn control of it over to the general public. Why let users control the interface? How much better could they make it? Wasn’t it clean enough?"
+— John Staats, ''The WoW Diary''
+</blockquote>
+Lua (/ˈluːə/ ''LOO-ə''; from Portuguese: ''lua'' [ˈlu(w)ɐ] meaning moon) is a lightweight, high-level, multi-paradigm programming language designed mainly for embedded use in applications.[ Lua is cross-platform software, since the interpreter of compiled bytecode is written in ANSI C,and Lua has a relatively simple C application programming interface (API) to embed it into applications.
 Lua originated in 1993 as a language for extending software applications to meet the increasing demand for customization at the time. It provided the basic facilities of most procedural programming languages, but more complicated or domain-specific features were not included; rather, it included mechanisms for extending the language, allowing programmers to implement such features. As Lua was intended to be a general embeddable extension language, the designers of Lua focused on improving its speed, portability, extensibility and ease-of-use in development.
+== WoW Lua ==
+By the release of 3.3.5a, Blizzard had made various helpful modifications to its version of Lua.
+=== Taint ===
+In WoW Lua, each variable contains a taint value, a string that identifies the AddOn from where the variable originated.
+=== Profiling ===
+Because each variable is taint-tagged by whichever AddOn generated it, WoW Lua is able to compute the memory usage of any particular AddOn.
+<pre>
+void   lua_gcupdatesizes(lua_State* L);
+lu_mem lua_gcgetsize(lua_State* L, const char* tag);
+</pre>
+Optionally, function performance can be profiled by turning on a flag (which is governed by the <code>scriptProfile</code> CVar).
+You can read the results of the function profiler with:
+<pre>
+void       lua_gcupdatetimes(lua_State* L);
+lua_Number lua_gcgettime(lua_State* L, const char* tag);
+void       lua_gcgetfunctiontime(lua_State* L, lua_Number* flat, lua_Number* total, int32_t* ncalls);
+void       lua_gcresettimes(lua_State* L);
+</pre>
+=== Standard library ===
+WoW Lua modifies the standard library by removing functions that expose the host filesystem, modifying existing functions, or adding new ones.
+These functions were removed from the standard library:
+* <code>dofile()</code>, <code>loadfile()</code> - Removed to prevent Lua from touching the host filesystem.
+* <code>load()</code> - Reason for removal unclear
+* <code>print()</code> - Removed to prevent Lua from touching stdout. This is replaced by a function that prints output to the ingame chat.
+* <code>math.randomseed()</code>
+* <code>string.sub()</code>
+These existing standard library functions were modified:
+* <code>getfenv()</code> - Implementation adds this code to end of function: <code>luaL_getmetafield(L, -1, "__environment");</code>
+* <code>string.upper()</code>, <code>string.lower()</code> - These were modified to support UTF-8 strings. Unlike stock Lua, they are able to convert special characters including Latin-1 and Cyrillic.
+These standard library functions were added by Blizzard:
+* <code>table.removemulti()</code>
+* <code>table.wipe()</code>