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diff --git a/moonscript.html.markdown b/moonscript.html.markdown new file mode 100644 index 00000000..193d7f97 --- /dev/null +++ b/moonscript.html.markdown @@ -0,0 +1,570 @@ +--- +language: moonscript +contributors: + - ["RyanSquared", "https://ryansquared.github.io/"] + - ["Job van der Zwan", "https://github.com/JobLeonard"] +filename: moonscript.moon +--- + +MoonScript is a dynamic scripting language that compiles into Lua. It gives +you the power of one of the fastest scripting languages combined with a +rich set of features. + +See [the MoonScript website](https://moonscript.org/) to see official guides on installation for all platforms. + +```moon +-- Two dashes start a comment. Comments can go until the end of the line. +-- MoonScript transpiled to Lua does not keep comments. + +-- As a note, MoonScript does not use 'do', 'then', or 'end' like Lua would and +-- instead uses an indented syntax, much like Python. + +-------------------------------------------------- +-- 1. Assignment +-------------------------------------------------- + +hello = "world" +a, b, c = 1, 2, 3 +hello = 123 -- Overwrites `hello` from above. + +x = 0 +x += 10 -- x = x + 10 + +s = "hello " +s ..= "world" -- s = s .. "world" + +b = false +b and= true or false -- b = b and (true or false) + +-------------------------------------------------- +-- 2. Literals and Operators +-------------------------------------------------- + +-- Literals work almost exactly as they would in Lua. Strings can be broken in +-- the middle of a line without requiring a \. + +some_string = "exa +mple" -- local some_string = "exa\nmple" + +-- Strings can also have interpolated values, or values that are evaluated and +-- then placed inside of a string. + +some_string = "This is an #{some_string}" -- Becomes 'This is an exa\nmple' + +-------------------------------------------------- +-- 2.1. Function Literals +-------------------------------------------------- + +-- Functions are written using arrows: + +my_function = -> -- compiles to `function() end` +my_function() -- calls an empty function + +-- Functions can be called without using parenthesis. Parentheses may still be +-- used to have priority over other functions. + +func_a = -> print "Hello World!" +func_b = -> + value = 100 + print "The value: #{value}" + +-- If a function needs no parameters, it can be called with either `()` or `!`. + +func_a! +func_b() + +-- Functions can use arguments by preceding the arrow with a list of argument +-- names bound by parentheses. + +sum = (x, y)-> x + y -- The last expression is returned from the function. +print sum(5, 10) + +-- Lua has an idiom of sending the first argument to a function as the object, +-- like a 'self' object. Using a fat arrow (=>) instead of a skinny arrow (->) +-- automatically creates a `self` variable. `@x` is a shorthand for `self.x`. + +func = (num)=> @value + num + +-- Default arguments can also be used with function literals: + +a_function = (name = "something", height=100)-> + print "Hello, I am #{name}.\nMy height is #{height}." + +-- Because default arguments are calculated in the body of the function when +-- transpiled to Lua, you can reference previous arguments. + +some_args = (x = 100, y = x + 1000)-> print(x + y) + +-------------------------------------------------- +-- Considerations +-------------------------------------------------- + +-- The minus sign plays two roles, a unary negation operator and a binary +-- subtraction operator. It is recommended to always use spaces between binary +-- operators to avoid the possible collision. + +a = x - 10 -- a = x - 10 +b = x-10 -- b = x - 10 +c = x -y -- c = x(-y) +d = x- z -- d = x - z + +-- When there is no space between a variable and string literal, the function +-- call takes priority over following expressions: + +x = func"hello" + 100 -- func("hello") + 100 +y = func "hello" + 100 -- func("hello" + 100) + +-- Arguments to a function can span across multiple lines as long as the +-- arguments are indented. The indentation can be nested as well. + +my_func 5, -- called as my_func(5, 8, another_func(6, 7, 9, 1, 2), 5, 4) + 8, another_func 6, 7, -- called as + 9, 1, 2, -- another_func(6, 7, 9, 1, 2) + 5, 4 + +-- If a function is used at the start of a block, the indentation can be +-- different than the level of indentation used in a block: + +if func 1, 2, 3, -- called as func(1, 2, 3, "hello", "world") + "hello", + "world" + print "hello" + +-------------------------------------------------- +-- 3. Tables +-------------------------------------------------- + +-- Tables are defined by curly braces, like Lua: + +some_values = {1, 2, 3, 4} + +-- Tables can use newlines instead of commas. + +some_other_values = { + 5, 6 + 7, 8 +} + +-- Assignment is done with `:` instead of `=`: + +profile = { + name: "Bill" + age: 200 + "favorite food": "rice" +} + +-- Curly braces can be left off for `key: value` tables. + +y = type: "dog", legs: 4, tails: 1 + +profile = + height: "4 feet", + shoe_size: 13, + favorite_foods: -- nested table + foo: "ice cream", + bar: "donuts" + +my_function dance: "Tango", partner: "none" -- :( forever alone + +-- Tables constructed from variables can use the same name as the variables +-- by using `:` as a prefix operator. + +hair = "golden" +height = 200 +person = {:hair, :height} + +-- Like in Lua, keys can be non-string or non-numeric values by using `[]`. + +t = + [1 + 2]: "hello" + "hello world": true -- Can use string literals without `[]`. + +-------------------------------------------------- +-- 3.1. Table Comprehensions +-------------------------------------------------- + +-- List Comprehensions + +-- Creates a copy of a list but with all items doubled. Using a star before a +-- variable name or table can be used to iterate through the table's values. + +items = {1, 2, 3, 4} +doubled = [item * 2 for item in *items] +-- Uses `when` to determine if a value should be included. + +slice = [item for item in *items when item > 1 and item < 3] + +-- `for` clauses inside of list comprehensions can be chained. + +x_coords = {4, 5, 6, 7} +y_coords = {9, 2, 3} + +points = [{x,y} for x in *x_coords for y in *y_coords] + +-- Numeric for loops can also be used in comprehensions: + +evens = [i for i=1, 100 when i % 2 == 0] + +-- Table Comprehensions are very similar but use `{` and `}` and take two +-- values for each iteration. + +thing = color: "red", name: "thing", width: 123 +thing_copy = {k, v for k, v in pairs thing} + +-- Tables can be "flattened" from key-value pairs in an array by using `unpack` +-- to return both values, using the first as the key and the second as the +-- value. + +tuples = {{"hello", "world"}, {"foo", "bar"}} +table = {unpack tuple for tuple in *tuples} + +-- Slicing can be done to iterate over only a certain section of an array. It +-- uses the `*` notation for iterating but appends `[start, end, step]`. + +-- The next example also shows that this syntax can be used in a `for` loop as +-- well as any comprehensions. + +for item in *points[1, 10, 2] + print unpack item + +-- Any undesired values can be left off. The second comma is not required if +-- the step is not included. + +words = {"these", "are", "some", "words"} +for word in *words[,3] + print word + +-------------------------------------------------- +-- 4. Control Structures +-------------------------------------------------- + +have_coins = false +if have_coins + print "Got coins" +else + print "No coins" + +-- Use `then` for single-line `if` +if have_coins then "Got coins" else "No coins" + +-- `unless` is the opposite of `if` +unless os.date("%A") == "Monday" + print "It is not Monday!" + +-- `if` and `unless` can be used as expressions +is_tall = (name)-> if name == "Rob" then true else false +message = "I am #{if is_tall "Rob" then "very tall" else "not so tall"}" +print message -- "I am very tall" + +-- `if`, `elseif`, and `unless` can evaluate assignment as well as expressions. +if x = possibly_nil! -- sets `x` to `possibly_nil()` and evaluates `x` + print x + +-- Conditionals can be used after a statement as well as before. This is +-- called a "line decorator". + +is_monday = os.date("%A") == "Monday" +print("It IS Monday!") if isMonday +print("It is not Monday..") unless isMonday +--print("It IS Monday!" if isMonday) -- Not a statement, does not work + +-------------------------------------------------- +-- 4.1 Loops +-------------------------------------------------- + +for i = 1, 10 + print i + +for i = 10, 1, -1 do print i -- Use `do` for single-line loops. + +i = 0 +while i < 10 + continue if i % 2 == 0 -- Continue statement; skip the rest of the loop. + print i + +-- Loops can be used as a line decorator, just like conditionals +print "item: #{item}" for item in *items + +-- Using loops as an expression generates an array table. The last statement +-- in the block is coerced into an expression and added to the table. +my_numbers = for i = 1, 6 do i -- {1, 2, 3, 4, 5, 6} + +-- use `continue` to filter out values +odds = for i in *my_numbers + continue if i % 2 == 0 -- acts opposite to `when` in comprehensions! + i -- Only added to return table if odd + +-- A `for` loop returns `nil` when it is the last statement of a function +-- Use an explicit `return` to generate a table. +print_squared = (t) -> for x in *t do x*x -- returns `nil` +squared = (t) -> return for x in *t do x*x -- returns new table of squares + +-- The following does the same as `(t) -> [i for i in *t when i % 2 == 0]` +-- But list comprehension generates better code and is more readable! + +filter_odds = (t) -> + return for x in *t + if x % 2 == 0 then x else continue +evens = filter_odds(my_numbers) -- {2, 4, 6} + +-------------------------------------------------- +-- 4.2 Switch Statements +-------------------------------------------------- + +-- Switch statements are a shorthand way of writing multiple `if` statements +-- checking against the same value. The value is only evaluated once. + +name = "Dan" + +switch name + when "Dave" + print "You are Dave." + when "Dan" + print "You are not Dave, but Dan." + else + print "You are neither Dave nor Dan." + +-- Switches can also be used as expressions, as well as compare multiple +-- values. The values can be on the same line as the `when` clause if they +-- are only one expression. + +b = 4 +next_even = switch b + when 1 then 2 + when 2, 3 then 4 + when 4, 5 then 6 + else error "I can't count that high! D:" + +-------------------------------------------------- +-- 5. Object Oriented Programming +-------------------------------------------------- + +-- Classes are created using the `class` keyword followed by an identifier, +-- typically written using CamelCase. Values specific to a class can use @ as +-- the identifier instead of `self.value`. + +class Inventory + new: => @items = {} + add_item: (name)=> -- note the use of fat arrow for classes! + @items[name] = 0 unless @items[name] + @items[name] += 1 + +-- The `new` function inside of a class is special because it is called when +-- an instance of the class is created. + +-- Creating an instance of the class is as simple as calling the class as a +-- function. Calling functions inside of the class uses \ to separate the +-- instance from the function it is calling. + +inv = Inventory! +inv\add_item "t-shirt" +inv\add_item "pants" + +-- Values defined in the class - not the new() function - will be shared across +-- all instances of the class. + +class Person + clothes: {} + give_item: (name)=> + table.insert @clothes name + +a = Person! +b = Person! + +a\give_item "pants" +b\give_item "shirt" + +-- prints out both "pants" and "shirt" + +print item for item in *a.clothes + +-- Class instances have a value `.__class` that are equal to the class object +-- that created the instance. + +assert(b.__class == Person) + +-- Variables declared in class body the using the `=` operator are locals, +-- so these "private" variables are only accessible within the current scope. + +class SomeClass + x = 0 + reveal: -> + x += 1 + print x + +a = SomeClass! +b = SomeClass! +print a.x -- nil +a.reveal! -- 1 +b.reveal! -- 2 + +-------------------------------------------------- +-- 5.1 Inheritance +-------------------------------------------------- + +-- The `extends` keyword can be used to inherit properties and methods from +-- another class. + +class Backpack extends Inventory + size: 10 + add_item: (name)=> + error "backpack is full" if #@items > @size + super name -- calls Inventory.add_item with `name`. + +-- Because a `new` method was not added, the `new` method from `Inventory` will +-- be used instead. If we did want to use a constructor while still using the +-- constructor from `Inventory`, we could use the magical `super` function +-- during `new()`. + +-- When a class extends another, it calls the method `__inherited` on the +-- parent class (if it exists). It is always called with the parent and the +-- child object. + +class ParentClass + @__inherited: (child)=> + print "#{@__name} was inherited by #{child.__name}" + a_method: (a, b) => print a .. ' ' .. b + +-- Will print 'ParentClass was inherited by MyClass' + +class MyClass extends ParentClass + a_method: => + super "hello world", "from MyClass!" + assert super == ParentClass + +-------------------------------------------------- +-- 6. Scope +-------------------------------------------------- + +-- All values are local by default. The `export` keyword can be used to +-- declare the variable as a global value. + +export var_1, var_2 +var_1, var_3 = "hello", "world" -- var_3 is local, var_1 is not. + +export this_is_global_assignment = "Hi!" + +-- Classes can also be prefixed with `export` to make them global classes. +-- Alternatively, all CamelCase variables can be exported automatically using +-- `export ^`, and all values can be exported using `export *`. + +-- `do` lets you manually create a scope, for when you need local variables. + +do + x = 5 +print x -- nil + +-- Here we use `do` as an expression to create a closure. + +counter = do + i = 0 + -> + i += 1 + return i + +print counter! -- 1 +print counter! -- 2 + +-- The `local` keyword can be used to define variables +-- before they are assigned. + +local var_4 +if something + var_4 = 1 +print var_4 -- works because `var_4` was set in this scope, not the `if` scope. + +-- The `local` keyword can also be used to shadow an existing variable. + +x = 10 +if false + local x + x = 12 +print x -- 10 + +-- Use `local *` to forward-declare all variables. +-- Alternatively, use `local ^` to forward-declare all CamelCase values. + +local * + +first = -> + second! + +second = -> + print data + +data = {} + +-------------------------------------------------- +-- 6.1 Import +-------------------------------------------------- + +-- Values from a table can be brought to the current scope using the `import` +-- and `from` keyword. Names in the `import` list can be preceded by `\` if +-- they are a module function. + +import insert from table -- local insert = table.insert +import \add from state: 100, add: (value)=> @state + value +print add 22 + +-- Like tables, commas can be excluded from `import` lists to allow for longer +-- lists of imported items. + +import + asdf, gh, jkl + antidisestablishmentarianism + from {} + +-------------------------------------------------- +-- 6.2 With +-------------------------------------------------- + +-- The `with` statement can be used to quickly call and assign values in an +-- instance of a class or object. + +file = with File "lmsi15m.moon" -- `file` is the value of `set_encoding()`. + \set_encoding "utf8" + +create_person = (name, relatives)-> + with Person! + .name = name + \add_relative relative for relative in *relatives +me = create_person "Ryan", {"sister", "sister", "brother", "dad", "mother"} + +with str = "Hello" -- assignment as expression! :D + print "original: #{str}" + print "upper: #{\upper!}" + +-------------------------------------------------- +-- 6.3 Destructuring +-------------------------------------------------- + +-- Destructuring can take arrays, tables, and nested tables and convert them +-- into local variables. + +obj2 = + numbers: {1, 2, 3, 4} + properties: + color: "green" + height: 13.5 + +{numbers: {first, second}, properties: {:color}} = obj2 + +print first, second, color -- 1 2 green + +-- `first` and `second` return [1] and [2] because they are as an array, but +-- `:color` is like `color: color` so it sets itself to the `color` value. + +-- Destructuring can be used in place of `import`. + +{:max, :min, random: rand} = math -- rename math.random to rand + +-- Destructuring can be done anywhere assignment can be done. + +for {left, right} in *{{"hello", "world"}, {"egg", "head"}} + print left, right +``` + +## Additional Resources + +- [Language Guide](https://moonscript.org/reference/) +- [Online Compiler](https://moonscript.org/compiler/) |