Candran ======= Candran is a dialect of the [Lua 5.3](http://www.lua.org) programming language which compiles to Lua 5.3, LuaJIT and Lua 5.1 compatible code. It adds several useful syntax additions which aims to make Lua faster and easier to write, and a simple preprocessor. Unlike Moonscript, Candran tries to stay close to the Lua syntax, and existing Lua code should be able to run on Candran unmodified. ````lua #import("lib.thing") -- static import #local debug or= false local function calculate(toadd=25) -- default parameters local result = thing.do() result += toadd #if debug then -- preprocessor conditionals print("Did something") #end return result end let a = { hey = true, method = :(foo, thing) -- short function declaration, with self @hey = thing(foo) -- @ as an alias for self end, selfReference = () -- short function declaration, without self return a -- no need for a prior local declaration when using let end } a:method(42, (foo) return "something " .. foo end) local odd = [ -- table comprehension for i=1, 10 do if i%2 == 0 then continue -- continue keyword end i -- implicit push end ] local count = [for i=1,10 i] -- single line statements local a = if condition then "one" else "two" end -- statement as expressions print("Hello %s":format("world")) -- methods calls on strings (and tables) litterals without enclosing parentheses ```` **Current status**: Candran is heavily used in several of my personal projects and works as expected. Candran is released under the MIT License (see ```LICENSE``` for details). #### Quick setup Install Candran automatically using LuaRocks: ```sudo luarocks install rockspec/candran-0.10.0-1.rockspec```. Or manually install LPegLabel (```luarocks install lpeglabel```, version 1.5 or above), download this repository and use Candran through the scripts in ```bin/``` or use it as a library with the self-contained ```candran.lua```. You can optionally install lua-linenoise (```luarocks install linenoise```) for an improved REPL. The rockspec does not install linenoise by default. You can register the Candran package searcher in your main Lua file (`require("candran").setup()`) and any subsequent `require` call in your project will automatically search for Candran modules. #### Editor support Most editors should be able to use their existing Lua support for Candran code. If you want full support for the additional syntax in your editor: * **Sublime Text 3**: * [sublime-candran](https://github.com/Reuh/sublime-candran) support the full Candran syntax * [SublimeLinter-candran-contrib](https://github.com/Reuh/SublimeLinter-contrib-candran) SublimeLinter plugin for Candran * **Atom**: [language-candran](https://atom.io/packages/language-candran) support the full Candran syntax The language ------------ ### Syntax additions After the preprocessor is run the Candran code is compiled to Lua. Candran code adds the folowing syntax to Lua: ##### Assignment operators * ````var += nb```` * ````var -= nb```` * ````var *= nb```` * ````var /= nb```` * ````var //= nb```` * ````var ^= nb```` * ````var %= nb```` * ````var ..= str```` * ````var and= str```` * ````var or= str```` * ````var &= nb```` * ````var |= nb```` * ````var <<= nb```` * ````var >>= nb```` For example, a ````var += nb```` assignment will be compiled into ````var = var + nb````. All theses operators can also be put right of the assigment operator, in which case ```var =+ nb``` will be compiled into ```var = nb + var```. Right and left operator can be used at the same time. **Please note** that the Lua code `a=-1` will be compiled into `a = 1 - a` and not `a = -1`! Write spaced code: `a = -1` works as expected. ##### Default function parameters ```lua function foo(bar = "default", other = thing.do()) -- stuff end ``` If an argument isn't provided or set to ```nil``` when the function is called, it will automatically be set to its default value. It is equivalent to doing ```if arg == nil then arg = default end``` for each argument at the start of the function. The default values can be any Lua expression, which will be evaluated in the function's scope each time the default value end up being used. ##### Short anonymous function declaration ```lua a = (arg1, arg2) print(arg1) end b = :(hop) print(self, hop) end ``` Anonymous function (functions values) can be created in a more concise way by omitting the ```function``` keyword. A ```:``` can prefix the parameters parenthesis to automatically add a ```self``` parameter. ##### `@` self aliases ```lua a = { foo = "Hoi" } function a:hey() print(@foo) -- Hoi print(@["foo"]) -- also works print(@ == self) -- true end ``` When a variable name is prefied with ```@```, the name will be accessed in ```self```. When used by itself, ```@``` is an alias for ```self```. ##### `let` variable declaration ```lua let a = { foo = function() print(type(a)) -- table end } ``` Similar to ```local```, but the variable will be declared *before* the assignemnt (i.e. it will compile into ```local a; a = value```), so you can access it from functions defined in the value. Can also be used as a shorter name for ```local```. ##### `continue` keyword ```lua for i=1, 10 do if i % 2 == 0 then continue end print(i) -- 1, 3, 5, 7, 9 end ``` Will skip the current loop iteration. ##### `push` keyword ```lua function a() for i=1, 5 do push i, "next" end return "done" end print(a()) -- 1, next, 2, next, 3, next, 4, next, 5, next, done push "hey" -- Does *not* work, because it is a valid Lua syntax for push("hey") ``` Add one or more value to the returned value list. If you use a `return` afterwards, the pushed values will be placed *before* the `return` values, otherwise the function will only return what was pushed. In particular, this keyword is useful when used through implicit `push` with table comprehension and statement expressions. **Please note** that, in order to stay compatible with vanilla Lua syntax, any `push` immediatly followed by a `"string expression"`, `{table expression}` or `(parenthesis)` will be interpreted as a function call. It's recommended to use the implicit `push` when possible. ##### Implicit `push` ```lua function a() for i=1, 5 do i, next end return "done" end print(a()) -- 1, next, 2, next, 3, next, 4, next, 5, next, done -- or probably more useful... local square = (x) x*x end -- function(x) return x*x end ``` Any list of expressions placed *at the end of a block* will be converted into a `push` automatically. **Please note** that this doesn't work with `v()` function calls, because these are already valid statements. Use `push v()` in this case. ##### Table comprehension ```lua a = [ for i=1, 10 do i end ] -- { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 } a = [ for i=1, 10 do if i%2 == 0 then @[i] = true end end ] -- { [2] = true, [4] = true, [6] = true, [8] = true, [10] = true } a = [push unpack(t1); push unpack(t2)] -- concatenate t1 and t2 ``` Comprehensions provide a shorter syntax for defining and initializing tables based on a block of code. You can write *any* code you want between `[` and `]`, this code will be run as if it was a separate function which is immediadtly run. Values returned by the function will be inserted in the generated table in the order they were returned. This way, each time you `push` value(s), they will be added to the table. The table generation function also have access to the `self` variable (and its alias `@`), which is the table which is being created, so you can set any of the table's field. ##### Suffixable string and table litterals ```lua "some text":upper() -- "SOME TEXT". Same as ("some text"):upper() in Lua. "string".upper -- the string.upper function. "string"["upper"] also works. {thing = 3}.thing -- 3. Also works with tables! [for i=0,5 do i*i end][3] -- 9. And table comprehensions! -- Functions calls have priority: someFunction"thing":upper() -- same as (someFunction("thing")):upper() (i.e., the way it would be parsed by Lua) ``` String litterals, table litterals, and comprehensions can be suffixed with `:` method calls, `.` indexing, or `[` indexing, without needing to be enclosed in parentheses. **Please note**, that "normal" functions calls have priority over this syntax, in order to maintain Lua compatibility. ##### Statement expressions ```lua a = if false then "foo" -- i.e. push "foo", i.e. return "foo" else "bar" end print(a) -- bar a, b, c = for i=1,2 do i end print(a, b, c) -- 1, 2, nil ``` `if`, `do`, `while`, `repeat` and `for` statements can be used as expressions. Their content will be run as if they were run in a separate function which is immediatly run. ##### One line statements ```lua if condition() a() elseif foo() b() if other() a() else -- "end" is always needed for else! c() end ``` `if`, `elseif`, `for`, and `while` statements can be written without `do`, `then` or `end`, in which case they contain a single statement. **Please note** that an `end` is always required for `else` blocks. ### Preprocessor Before compiling, Candran's preprocessor is run. It execute every line starting with a _#_ (ignoring prefixing whitespace, long strings and comments) as Candran code. For example, ````lua #if lang == "fr" then print("Bonjour") #else print("Hello") #end ```` Will output ````print("Bonjour")```` or ````print("Hello")```` depending of the "lang" argument passed to the preprocessor. The preprocessor has access to the following variables: * ````candran````: the Candran library table. * ````output````: the current preprocessor output string. Can be redefined at any time. * ````import(module[, [options])````: a function which import a module. This should be equivalent to using _require(module)_ in the Candran code, except the module will be embedded in the current file. _options_ is an optional preprocessor arguments table for the imported module (current preprocessor arguments will be inherited). Options specific to this function: ```loadLocal``` (default ```true```): ```true``` to automatically load the module into a local variable (i.e. ```local thing = require("module.thing")```); ```loadPackage``` (default ```true```): ```true``` to automatically load the module into the loaded packages table (so it will be available for following ```require("module")``` calls). * ````include(filename)````: a function which copy the contents of the file _filename_ to the output. * ````write(...)````: write to the preprocessor output. For example, ````#write("hello()")```` will output ````hello()```` in the final file. * ```placeholder(name)```: if the variable _name_ is defined in the preprocessor environement, its content will be inserted here. * ````...````: each arguments passed to the preprocessor is directly available in the environment. * and every standard Lua library. Compile targets --------------- Candran is based on the Lua 5.3 syntax, but can be compiled to Lua 5.3, LuaJIT, and Lua 5.1 compatible code. To chose a compile target, set the ```target``` option to ```lua53```, ```luajit```, or ```lua51``` in the option table when using the library or the command line tools. Candran will try to detect the currently used Lua version and use it as the default target. For the ```luajit``` and ```lua51``` targets, Lua 5.3 specific syntax (bitwise operators, integer division) will automatically be translated to valid Lua 5.1 syntax, using LuaJIT's ```bit``` library if necessary. Unless LuaJIT's bit library is installed, you won't be able to use bitwise operators with vanilla Lua 5.1 ("PUC Lua"). The ```lua51``` target does not support gotos and labels. **Please note** that Candran only translates syntax, and will not try to do anything about changes in the Lua standard library (for example, the new utf8 module). If you need this, you should be able to use [lua-compat-5.3](https://github.com/keplerproject/lua-compat-5.3) along with Candran. Usage ----- ### Command-line usage The library can be used standalone through the ```canc``` and ```can``` utility: * ````canc```` Display the information text (version and basic command-line usage). * ````canc [options] filename...```` Preprocess and compile each _filename_ Candran files, and creates the assiociated ```.lua``` files in the same directories. _options_ is of type ````-somearg -anotherarg thing=somestring other=5````, which will generate a Lua table ```{ somearg = true, anotherarg = true, thing = "somestring", other = 5 }```. You can choose to use another directory where files should be written using the ```dest=destinationDirectory``` argument. You can choose the output filename using ```out=filename```. By default, compiled files have the same name as their input file, but with a ```.lua``` extension. ```canc``` can write to the standard output instead of creating files using the ```-print``` argument. You can choose to run only the preprocessor or compile using the ```-preprocess``` and ```-compile``` flags. You can choose to only parse the file and check it for syntaxic errors using the ```-parse``` flag. Errors will be printed to stderr in a similar format to ```luac -p```. The ```-ast``` flag is also available for debugging, and will disable preprocessing, compiling and file writing, and instead directly dump the AST generated from the input file(s) to stdout. Instead of providing filenames, you can use ```-``` to read from standard input. Use the ```-h``` or ```-help``` option to display a short help text. Example uses: * ````canc foo.can```` preprocess and compile _foo.can_ and write the result in _foo.lua_. * ````canc indentation=" " foo.can```` preprocess and compile _foo.can_ with 2-space indentation (readable code!) and write the result in _foo.lua_. * ````canc foo.can -verbose -print | lua```` preprocess _foo.can_ with _verbose_ set to _true_, compile it and execute it. * ````canc -parse foo.can```` checks foo.can for syntaxic errors. * ```can``` Start a simplisitic Candran REPL. If you want a better REPL (autocompletion, history, ability to move the cursor), install lua-linenoise: ```luarocks install linenoise```. * ````can [options] filename```` Preprocess, compile and run _filename_ using the options provided. This will automatically register the Candran package searcher, so required Candran modules will be compiled as they are needed. This command will use error rewriting unless explicitely enabled (by setting the `rewriteErrors=false` option). Instead of providing a filename, you can use ```-``` to read from standard input. Use the ```-h``` or ```-help``` option to display a short help text. ### Library usage Candran can also be used as a Lua library: ````lua local candran = require("candran") -- load Candran local f = io.open("foo.can") -- read the file foo.can local contents = f:read("*a") f:close() local compiled = candran.make(contents, { debug = true }) -- compile foo.can with debug set to true load(compiled)() -- execute! -- or simpler... candran.dofile("foo.can") -- or, if you want to be able to directly load Candran files using require("module") candran.setup() local foo = require("foo") ```` The table returned by _require("candran")_ gives you access to: ##### Compiler & preprocessor * ````candran.VERSION````: Candran's version string (e.g. `"0.10.0"`). * ````candran.preprocess(code[, options])````: return the Candran code _code_, preprocessed with the _options_ options table. * ````candran.compile(code[, options])````: return the Candran code compiled to Lua with the _options_ option table. * ````candran.make(code[, options])````: return the Candran code, preprocessed and compiled with the _options_ options table. ##### Code loading helpers * ```candran.loadfile(filepath, env, options)```: Candran equivalent to the Lua 5.3's loadfile funtion. Will rewrite errors by default. * ```candran.load(chunk, chunkname, env, options)```: Candran equivalent to the Lua 5.3's load funtion. Will rewrite errors by default. * ```candran.dofile(filepath, options)```: Candran equivalent to the Lua 5.3's dofile funtion. Will rewrite errors by default. #### Error rewriting When using the command-line tools or the code loading helpers, Candran will automatically setup error rewriting: because the code is reformated when compiled and preprocessed, lines numbers given by Lua in case of error are hardly usable. To fix that, Candran map each line from the compiled file to the lines from the original file(s), inspired by MoonScript. Errors will be displayed as: ``` example.can:12(5): attempt to call a nil value (global 'iWantAnError') ``` 12 is the line number in the original Candran file, and 5 is the line number in the compiled file. If you are using the preprocessor ```import()``` function, the source Candran file and destination Lua file might not have the same name. In this case, the error will be: ``` example.can:12(final.lua:5): attempt to call a nil value (global 'iWantAnError') ``` You can perform error rewriting manually using: * ```candran.messageHandler(message)```: the error message handler used by Candran. Given `message` the Lua error string, returns full Candran traceback where soure files and lines are rewritten to their Candran source. You can use it as is in xpcall as a message handler. ##### Package searching helpers Candran comes with a custom package searcher which will automatically find, preprocesses and compile ```.can``` files. If you want to use Candran in your project without worrying about compiling the files, you can simply call ```lua require("candran").setup() ``` at the top of your main Lua file. If a Candran file is found when you call ```require()```, it will be automatically compiled and loaded. If both a Lua and Candran file match a module name, the Candran file will be loaded. * ```candran.searcher(modpath)```: Candran package searcher function. Use the existing package.path. * ```candran.setup()```: register the Candran package searcher, and return the `candran` table. ##### Available compiler & preprocessor options You can give arbitrary options to the compiler and preprocessor, but Candran already provide and uses these with their associated default values: ```lua target = "lua53" -- compiler target. "lua53", "luajit" or "lua51" (default is automatically selected based on the Lua version used). indentation = "" -- character(s) used for indentation in the compiled file. newline = "\n" -- character(s) used for newlines in the compiled file. variablePrefix = "__CAN_" -- Prefix used when Candran needs to set a local variable to provide some functionality (example: to load LuaJIT's bit lib when using bitwise operators). mapLines = true -- if true, compiled files will contain comments at the end of each line indicating the associated line and source file. Needed for error rewriting. chunkname = "nil" -- the chunkname used when running code using the helper functions and writing the line origin comments. Candran will try to set it to the original filename if it knows it. rewriteErrors = true -- true to enable error rewriting when loading code using the helper functions. Will wrap the whole code in a xpcall(). ``` You can change the defaults used for these variables in the table `candran.default`. There are also a few function-specific options available, see the preprocessor functions documentation for more information. ### Compiling the library The Candran library itself is written is Candran, so you have to compile it with an already compiled Candran library. The compiled _candran.lua_ should include every Lua library needed to run it. You will still need to install LPegLabel. This command will use the precompilled version of this repository (_candran.lua_) to compile _candran.can_ and write the result in _candran.lua_: ```` canc candran.can ```` You can then run the tests on your build: ```` cd test lua test.lua ../candran.lua ````