Fixed readme
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README.md
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README.md
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<!--- THIS IS AN AUTO-GENERATED FILE --->
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<!--- MANUAL CHANGES CAN AND WILL BE OVERWRITTEN --->
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# Pretty
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pretty is an advanced pretty printer for Lua.
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# pretty is an advanced pretty printer for Lua.
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It's primarily a
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debugging tool, aiming for human readability, by detecting pattern in the input
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data, and creating an output string utilizing and highlighting those patterns.
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debugging tool, aiming for human readability, by detecting pattern in the input
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data, and creating an output string utilizing and highlighting those patterns.
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## Code Example
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Setup is simple, use pretty = require 'pretty', and you're good to go.
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```lua
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> print(pretty( { 1, 2, 3 } ))
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{ 1, 2, 3 }
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> print(pretty( { hello = 'world', num = 42 } ))
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{
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num = 42
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hello = 'world'
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$ print(pretty( { 1, 2, 3 } ))
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{ 1, 2, 3 }
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$ print(pretty( { hello = 'world', num = 42 } ))
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{
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num = 42
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hello = 'world'
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}
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> print(pretty( { abs = math.abs, max = math.max, some = function() end } ))
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{
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abs = builtin function (x) ... end
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max = builtin function (x, ...) ... end
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some = function () ... end
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$ print(pretty( { abs = math.abs, max = math.max, some = function() end } ))
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{
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abs = builtin function (x) ... end
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max = builtin function (x, ...) ... end
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some = function () ... end
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}
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> print(pretty( math.abs ))
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builtin function (x)
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-- math.abs
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-- Returns the absolute value of x
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...
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$ print(pretty( math.abs ))
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builtin function (x)
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-- math.abs
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-- Returns the absolute value of x
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...
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end
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```
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## Motivation
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This project is the outcome of my frustration with existing pretty printers, and
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a desire to expand upon the pretty printer I developed for
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Xenoterm. The original Xenoterm pretty
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printer was much simpler than pretty - and the current is even simpler - but
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the enhancements I make, when compared to other pretty printers, inspired me to
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create pretty.
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a desire to expand upon the pretty printer I developed for
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Xenoterm. The original Xenoterm pretty
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printer was much simpler than pretty - and the current is even simpler - but
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the enhancements I make, when compared to other pretty printers, inspired me to
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create pretty.
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pretty sorts it's priorities like so:
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@ -62,209 +52,47 @@ Lua-compatible output.
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Customization.
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I'd rather have good defaults than provide a ton of customization options. If an
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structure avoids easy representation in Lua, I'd rather extend the syntax, than
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lose the info.
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structure avoids easy representation in Lua, I'd rather extend the syntax, than
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lose the info.
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Another aspect where pretty shines is in exploratory programming, when
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attempting to avoid reliance on outside documentation. The amount of information
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pretty exposes varies by the data you are inspecting. If you're inspecting
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a list of functions, their function signatures are visible, but if you're
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inspecting a single function, documentation and source location may appear if
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available.
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attempting to avoid reliance on outside documentation. The amount of information
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pretty exposes varies by the data you are inspecting. If you're inspecting
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a list of functions, their function signatures are visible, but if you're
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inspecting a single function, documentation and source location may appear if
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available.
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## Features
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Written in good-old pureblood Lua, with support for PUC Lua 5.0+ and
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LuaJIT 2.0+.
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Written in good-old pure-blood Lua, with support for PUC Lua 5.0+ and LuaJIT 2.0+.
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Redefining what it means to be "human readable":
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Is multi-line centric, to aid readability.
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Indention and alignment of keys-value pairs.
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Keys-value pairs are
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alpha-numerically sorted by key
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type and thereafter alphabetically.
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The format and structure of output changes depending upon the input. Maps
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appear differently to deeply nested tables to long sequences with short
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strings to short lists.
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Uses the standard debug library to gain information about functions and
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other advanced structures.
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* Is multi-line centric, to aid readablitiy.
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* Indention and alignment of keys-value pairs.
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* Keys-value pairs are [properly](http://www.davekoelle.com/alphanum.html)
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sorted by key type and thereafter alphabetically.
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* The format and structure of output changes depending upon the input.
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Maps appear differently to deeply nested tables to long sequences
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with short strings to short lists.
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* Uses the standard debug library to gain information about functions
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and other advanced structures.
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Installation
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## Installation
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pretty is loadable directly with require. Either clone or download this
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repository. Where you place it, depends upon what you want to do:
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repository. Where you place it, depends upon what you want to do:
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**You want pretty in a specific project**: Place the pretty folder
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somewhere in your project, and require it from one of your project files.
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somewhere in your project, and require it from one of your project files.
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**You want pretty on your system**: Place the pretty folder such that
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it's visible from your Lua-path. On my system this might be
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/usr/local/share/lua/5.1/. Now you can require it from anywhere.
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it's visible from your Lua-path. On my system this might be
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/usr/local/share/lua/5.1/. Now you can require it from anywhere.
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API Documentation
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## API Documentation
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pretty exposes a single function, the pretty function itself. It's function
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signature is pretty(value, options). value can be any Lua value. options
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must be a table.
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### List of options
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pretty is sure to complain if you give it an unknown option, or if you give an
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option a bad value.
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indent: string: The string to indent with. Four spaces by default.
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## TODO
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Tasks to be done before pretty can be called version 1.0.0, in order of
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priority:
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Add a dedicated unicode submodule, to handle some minor alignment and
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character escaping issues. pretty should escape all malformed unicode
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sequences.
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Align numbers towards right for tabular views.
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Add support for setmetatable, and exploring values in metatables.
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Provide nice formatting for cdata datatype in LuaJIT.
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Find a better name than pretty.
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Enhance internal structure some amount. See TODO markers in files.
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It would be nice to have the following, but these are secondary:
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Add option for colored output. Primarily syntax highlighting, but also
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[BlueJ-style](www.bluej.org/about.html) scope highlighting, with some faint
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background colors.
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Expand on the comment output in output, for __tostring methods, and global
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namespaces like io or math.
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Fit output within a predefined width limit. Default to 80.
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Look into tool for understanding complex structures with recursive
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definitions. Whatever modes are thought up, they should be automatic modes,
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not an options. Should at least include modes for self-referential tables
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and Directed-Acyclic-Graphs.
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Alternative pretty printers
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pretty is large, slow, and requires the debug library to work. It's not
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designed for serialization purposes, nor is it concerned with offering the same
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level of customization as other libraries do.
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If you want a sleek, fast, customizable or embeddable library, there are
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thankfully other options.
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inspect.lua: One of the classic debugging
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pretty printers.
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pprint.lua: Reimplementation of inspect.lua
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serpent: Advanced and fast pretty printer.
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pluto: Can serialize arbitrary parts of
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Lua, including functions, upvalues, and proper lexical scoping. Not written
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in native Lua.
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binser: Library for special purpose
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serialization.
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Even more are available at the lua-users wiki.
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## Thoughts on displaying tables in an intuitive way.
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Lua's table data-structure is likely to be the most concise data structure ever
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invented. (If not, please send me a link!) Lists, maps, objects, classes,
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proxies, etc. This obviously brings about it some difficulty when attempting to
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represent these tables. What do we want to highlight, and what do we choose to
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avoid?
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One notable issue is whether to show every key that a table answers (to lift
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some Smalltalk terms) to, or to just display those it contains. That is, do we
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think about __index in the table's metatable and what it returns, or do we
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ignore __index? For cases where __index is a function, we cannot say
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anything about the keys that the table answers to. If __index is a table, we
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have a better idea, but it would be cluttered to display both types of keys side
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by side.
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Native representation: Lua's native representation includes the type and
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address of the table. It allows for distinguishing between unique tables,
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but won't tell us anything about the contents.
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Omission: By representing tables as the pseudo-parsable {...}, it's
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clear we are talking about a table. We disregard the ability to
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distinguish between tables.
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2A. If the table is empty, we could represent it as {}. But what if the table
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has a metatable with __index defined? We could continue to represent it as
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{}, but {...} would be more "honest".
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Single-line: TODO
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Multi-line: TODO
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Columns: For some highly-regular structures, like lists of short strings,
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giving each string it's own line would be too long, but formatting them as a
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single-line list would be too cluttered. Thus we can take inspiration from
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the classic ls unix tool, and place the output into columns, to help guide
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the eyes.
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Tabular: Other structures are formatted like actual tables of data, e.g. a
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sequence of tuples, like one would see in an SQL database. For these
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structures it's an obvious choice to align them based on the keys.
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Pseudo-Tabular: Some structures are almost tabular, e.g. they are sequences
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of tuples, but some of the tuples differ in their structure. For these
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structures it's still useful to tabulate the keys that all tuples share. To
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do this we should sort the key order descending by the number of tuples with
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the key.
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But what do we do about the the outlier keys? We can either justify the
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entire table, and give specific spots for the outlier keys, thereby
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significantly increasing the size of the table, or we can leave the table
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unjustified, abandoning it's eye-guiding attributes.
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Special cases: (Array-tree, Table-Tree, Linked-List, Predictive Sequences) TODO
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signature is pretty(value, options). value can be any Lua value. options
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must be a table.
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@ -14,20 +14,20 @@ Setup is simple, use `pretty = require 'pretty'`, and you're good to go.
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$ print(pretty( { 1, 2, 3 } ))
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{ 1, 2, 3 }
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> print(pretty( { hello = 'world', num = 42 } ))
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$ print(pretty( { hello = 'world', num = 42 } ))
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{
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num = 42
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hello = 'world'
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}
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> print(pretty( { abs = math.abs, max = math.max, some = function() end } ))
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$ print(pretty( { abs = math.abs, max = math.max, some = function() end } ))
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{
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abs = builtin function (x) ... end
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max = builtin function (x, ...) ... end
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some = function () ... end
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}
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> print(pretty( math.abs ))
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$ print(pretty( math.abs ))
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builtin function (x)
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-- math.abs
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-- Returns the absolute value of x
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