YueScript

https://yuescript.org/doc
Admin
YueScript is a dynamic language and MoonScript dialect that compiles to Lua. It aims to provide...
Tokens:21,699
Snippets:182
Trust Score:6
Update:1 year ago
Show doc for...
Tokens:
Raw
### YueScript Installation: LuaRocks, Shared Library, and Binary Tool Builds

Source: https://yuescript.org/doc/index

Provides various shell commands for installing YueScript. This includes using LuaRocks for module installation, building a shared library (`yue.so`), and compiling the binary tool with options to disable macros or built-in Lua.

```Shell
luarocks install yuescript
```

```Shell
make shared LUAI=/usr/local/include/lua LUAL=/usr/local/lib/lua
```

```Shell
make install
```

```Shell
make install NO_MACRO=true
```

```Shell
make install NO_LUA=true
```

--------------------------------

### YueScript Command Line Tool Options and Usage

Source: https://yuescript.org/doc/index

This section details the command-line interface for the YueScript compiler and runtime. It lists all available options for compilation, execution, debugging, and output control, along with practical usage examples.

```APIDOC
Usage: yue [options|files|directories] ...

   -h       Print this message
   -e str   Execute a file or raw codes
   -m       Generate minified codes
   -r       Rewrite output to match original line numbers
   -t path  Specify where to place compiled files
   -o file  Write output to file
   -s       Use spaces in generated codes instead of tabs
   -p       Write output to standard out
   -b       Dump compile time (doesn't write output)
   -g       Dump global variables used in NAME LINE COLUMN
   -l       Write line numbers from source codes
   -j       Disable implicit return at end of file
   -c       Reserve comments before statement from source codes
   -w path  Watch changes and compile every file under directory
   -v       Print version
   --       Read from standard in, print to standard out
            (Must be first and only argument)

   --target=version  Specify the Lua version codes the compiler will generate
                     (version can only be 5.1, 5.2, 5.3 or 5.4)
   --path=path_str   Append an extra Lua search path string to package.path

   Execute without options to enter REPL, type symbol '$'
   in a single line to start/stop multi-line mode

Usage Examples:

   yue .: Recursively compile every YueScript file with extension .yue under current path.
   yue -t /target/path/ .: Compile and save results to a target path.
   yue -l .: Compile and reserve debug info.
   yue -m .: Compile and generate minified codes.
   yue -e 'print 123': Execute raw codes.
   yue -e main.yue: Execute a YueScript file.
```

--------------------------------

### YueScript With Statement: Object Initialization in a Function

Source: https://yuescript.org/doc/index

Shows how to use the `with` statement within a function to create and configure an object based on function parameters. This example demonstrates creating a `Person` object and adding relatives dynamically.

```YueScript
create_person = (name,  relatives) ->
  with Person!
    .name = name
    \add_relative relative for relative in *relatives

me = create_person "Leaf", [dad, mother, sister]
```

--------------------------------

### Yuescript List Comprehension: Filtering with `when` Clause

Source: https://yuescript.org/doc/index

Illustrates how to filter elements in a list comprehension using a `when` clause. This example selects items based on their index, creating a sub-list.

```Yuescript
slice = [item for i, item in ipairs items when i > 1 and i < 3]
```

--------------------------------

### YueScript Macro for Inserting Raw Codes

Source: https://yuescript.org/doc/index

This example illustrates how YueScript macros can be used to insert raw code directly into the compiled output. Macros can return either a YueScript string or a configuration table specifying raw Lua code, providing a powerful mechanism for interop with Lua.

```YueScript
macro yueFunc = (var) -> "local #{var} = ->"
$yueFunc funcA
funcA = -> "fail to assign to the Yue macro defined variable"

macro luaFunc = (var) -> {
  code: "local function #{var}() end"
  type: "lua"
}
$luaFunc funcB
funcB = -> "fail to assign to the Lua macro defined variable"

macro lua = (code) -> {
  :code
  type: "lua"
}

-- the raw string leading and ending symbols are auto trimed
$lua[==[
-- raw Lua codes insertion
if cond then
  print("output")
end
]==]
```

--------------------------------

### Chaining Function Calls with Operators in YueScript

Source: https://yuescript.org/doc/index

Demonstrates the use of special operators `\` and `::` in YueScript for chaining function calls, providing a more fluent syntax similar to method calls in object-oriented languages. The examples include conditional execution based on a nil check.

```YueScript
tb\func! if tb ~= nil
tb::func! if tb != nil
```

--------------------------------

### Implement class inheritance and method overriding in YueScript

Source: https://yuescript.org/doc/index

Demonstrates how to extend an existing class in YueScript using the `extends` keyword, enabling inheritance of properties and methods. The example also shows how to override a parent method (`add_item`) and how to call the overridden parent method using `super`.

```YueScript
class BackPack extends Inventory
  size: 10
  add_item: (name) =>
    if #@items > size then error "backpack is full"
    super name
```

--------------------------------

### YueScript With Statement: Basic Object Initialization

Source: https://yuescript.org/doc/index

Demonstrates the basic usage of the `with` statement in YueScript to initialize an object by setting properties and calling methods without repeating the object's name. This example shows property assignment (`.name`), method invocation (`\add_relative`, `\save!`), and accessing properties within the `with` block.

```YueScript
with Person!
  .name = "Oswald"
  \add_relative my_dad
  \save!
  print .name
```

--------------------------------

### Object Destructuring with Renaming and Shorthand in Yuescript

Source: https://yuescript.org/doc/index

Shows how to extract values from object-like tables by key. Includes examples of renaming extracted variables and using the shorthand `:` prefix when the variable name matches the key, as well as mixing both syntaxes.

```Yuescript
obj = {
  hello: "world"
  day: "tuesday"
  length: 20
}

{hello: hello, day: the_day} = obj
print hello, the_day

:day = obj -- OK to do simple destructuring without braces
```

```Yuescript
{:concat, :insert} = table
```

```Yuescript
{:mix, :max, random: rand} = math
```

--------------------------------

### Yuescript Error Handling with try?

Source: https://yuescript.org/doc/index

Demonstrates the 'try?' keyword for simplified error handling in Yuescript. It returns the result on success and 'nil' on failure, omitting the boolean status. Examples include usage with nil coalescing, as a function argument, and with an explicit 'catch' block.

```Yuescript
a, b, c = try? func!

-- with nil coalescing operator
a = (try? func!) ?? "default"

-- as function argument
f try? func!

-- with catch block
f try?
  print 123
  func!
catch e
  print e
  e
```

--------------------------------

### For Loop - As an Expression with Break Return Value

Source: https://yuescript.org/doc/index

Demonstrates using 'break' with a return value within a 'for' loop expression, allowing the loop to exit early and return a meaningful result. The example finds the first number greater than 10.

```Yuescript
first_large = for n in *numbers
  break n if n > 10
```

--------------------------------

### Continue Statement - Basic Usage in Loops

Source: https://yuescript.org/doc/index

Explains the 'continue' statement, which skips the current iteration of a loop and proceeds to the next. The example demonstrates printing only odd numbers within a loop.

```Yuescript
i = 0
while i < 10
  i += 1
  continue if i % 2 == 0
  print i
```

--------------------------------

### For Loop - As an Expression with Accumulation

Source: https://yuescript.org/doc/index

Explains how 'for' loops can be used as expressions, where the last statement in the body is coerced into an expression and accumulated into an array table. The example doubles even numbers.

```Yuescript
doubled_evens = for i = 1, 20
  if i % 2 == 0
    i * 2
  else
    i
```

--------------------------------

### YueScript Do Expression: Combining Multiple Lines

Source: https://yuescript.org/doc/index

Demonstrates `do` as an expression, allowing multiple lines of code to be combined into a single expression. The result of the `do` expression is the value of its last statement. This example creates a counter closure.

```YueScript
counter = do
  i = 0
  ->
    i += 1
    i

print counter!
print counter!
```

--------------------------------

### Yuescript Table Field Matching and Conditional Destructuring

Source: https://yuescript.org/doc/index

Shows how to match against specific fields within a table and conditionally destructure them based on their values. This example uses boolean checks (`success: true`) and captures associated result fields.

```Yuescript
switch tb
  when success: true, :result
    print "success", result
  when success: false
    print "failed", result
  else
    print "invalid"
```

--------------------------------

### YueScript Language Features: Imports, Literals, Comprehension, Pipe, Metatables

Source: https://yuescript.org/doc/index

This comprehensive example showcases core YueScript language features. It includes import syntax, object and array literals, functional programming constructs like list comprehension (map, filter, reduce), the pipe operator for chaining operations, metatable manipulation, and JavaScript-like export syntax for modules.

```YueScript
-- import syntax
import p, to_lua from "yue"

-- object literals
inventory =
  equipment:
    - "sword"
    - "shield"
  items:
    - name: "potion"
      count: 10
    - name: "bread"
      count: 3

-- list comprehension
map = (arr, action) ->
  [action item for item in *arr]

filter = (arr, cond) ->
  [item for item in *arr when cond item]

reduce = (arr, init, action): init ->
  init = action init, item for item in *arr

-- pipe operator
[1, 2, 3]
  |> map (x) -> x * 2
  |> filter (x) -> x > 4
  |> reduce 0, (a, b) -> a + b
  |> print

-- metatable manipulation
apple =
  size: 15
  <index>:
    color: 0x00ffff

with apple
  p .size, .color, .<index> if .<>?

-- js-like export syntax
export 🌛 = "月之脚本"
```

--------------------------------

### Yuescript Basic Variable Assignment

Source: https://yuescript.org/doc/index

Illustrates fundamental variable assignment in Yuescript. Variables are dynamically typed and are defined as local by default. Examples include single variable assignment, multiple variable assignment, and re-assignment to existing variables.

```Yuescript
hello = "world"
a, b, c = 1, 2, 3
hello = 123 -- uses the existing variable
```

--------------------------------

### Yuescript Switch Statement as an Expression

Source: https://yuescript.org/doc/index

Illustrates how a Yuescript switch statement can be used as an expression, where its evaluated result is assigned to a variable. This example shows different return values based on 'when' conditions and an 'else' block for handling unmatchable scenarios or errors.

```Yuescript
b = 1
next_number = switch b
  when 1
    2
  when 2
    3
  else
    error "can't count that high!"

```

--------------------------------

### Generating Macros with Macros in YueScript

Source: https://yuescript.org/doc/index

Explains how YueScript allows for advanced compile-time code generation by defining macros that produce other macros. This example creates an `Enum` macro that generates a type-checking macro (`BodyType`), ensuring valid enum values at compile time.

```YueScript
macro Enum = (...) ->
	items = {...}
	itemSet = {item, true for item in *items}
	(item) ->
		error "got \"#{item}\", expecting one of #{table.concat items, ', '}" unless itemSet[item]
		"\"#{item}\""

macro BodyType = $Enum(
	Static
	Dynamic
	Kinematic
)

print "Valid enum type:", $BodyType Static
-- print "Compilation error with enum type:", $BodyType Unknown
```

--------------------------------

### Controlling Specific Variable Updates with 'using' in YueScript

Source: https://yuescript.org/doc/index

This YueScript example illustrates how to explicitly specify which variables from the enclosing scope a function is allowed to modify using the '(add using k, i)' syntax. It shows that 'tmp' is created as a new local variable, while 'k' and 'i' are updated in the outer scope.

```YueScript
tmp = 1213
i, k = 100, 50

my_func = (add using k, i) ->
  tmp = tmp + add -- a new local tmp is created
  i += tmp
  k += tmp

my_func(22)
print i, k -- these have been updated
```

--------------------------------

### Apply Constructor Property Promotion to Functions in Yuescript

Source: https://yuescript.org/doc/index

Demonstrates how constructor property promotion can be applied to functions in Yuescript, providing a concise way to initialize object fields directly from function arguments, similar to class constructors.

```Yuescript
new = (@fieldA, @fieldB) => @
obj = new {}, 123, "abc"
print obj
```

--------------------------------

### Create class instances and invoke methods in YueScript

Source: https://yuescript.org/doc/index

Illustrates how to instantiate a YueScript class by calling its name as a function. It also shows the syntax for invoking methods on an instance using the `\` operator, which correctly passes the instance as the first argument to the method.

```YueScript
inv = Inventory!
inv\add_item "t-shirt"
inv\add_item "pants"
```

--------------------------------

### Yuescript Table Comprehension: Copying Key-Value Pairs

Source: https://yuescript.org/doc/index

Introduces table comprehensions, showing how to copy all key-value pairs from an existing table into a new one using `pairs` for iteration.

```Yuescript
thing = {
  color: "red"
  name: "fast"
  width: 123
}

thing_copy = {k, v for k, v in pairs thing}
```

--------------------------------

### Yuescript List Slicing: Omitting Maximum Bound

Source: https://yuescript.org/doc/index

Demonstrates list slicing where the maximum index bound is omitted, defaulting to the end of the table, useful for taking elements from a specific start index to the end.

```Yuescript
slice = [item for item in *items[2,]]
```

--------------------------------

### Basic Table Matching and Destructuring in Yuescript

Source: https://yuescript.org/doc/index

Demonstrates how to use `switch when` to match and destructure tables based on the presence of specific keys. It shows how to extract values from matched structures into local variables.

```Yuescript
items =
  * x: 100
    y: 200
  * width: 300
    height: 400

for item in *items
  switch item
    when :x, :y
      print "Vec2 #{x}, #{y}"
    when :width, :height
      print "size #{width}, #{height}"
```

--------------------------------

### Loading YueScript Entry Files as Lua Modules

Source: https://yuescript.org/doc/index

Demonstrates the simplest way to integrate YueScript into a Lua project by requiring a `.yue` entry file directly. This method handles on-the-fly compilation and ensures correct line number reporting in error messages.

```Lua
require("yue")("your_yuescript_entry")
```

--------------------------------

### Utilize Constructor Property Promotion in Yuescript Classes

Source: https://yuescript.org/doc/index

Explains Yuescript's constructor property promotion syntax, which significantly reduces boilerplate code by allowing direct assignment of constructor arguments to instance ('@') and class ('@@') variables upon object instantiation.

```Yuescript
class Something
  new: (@foo, @bar, @@biz, @@baz) =>

-- Which is short for

class Something
  new: (foo, bar, biz, baz) =>
    @foo = foo
    @bar = bar
    @@biz = biz
    @@baz = baz
```

--------------------------------

### Demonstrating Destructive Assignment in YueScript

Source: https://yuescript.org/doc/index

This YueScript example illustrates how a variable 'i' declared in an outer scope can be accidentally overwritten within a function, leading to unintended side effects. It highlights the need for mechanisms to control variable assignment.

```YueScript
i = 100

-- many lines of code...

my_func = ->
  i = 10
  while i > 0
    print i
    i -= 1

my_func!

print i -- will print 0
```

--------------------------------

### Execute YueScript Code from File

Source: https://yuescript.org/doc/index

Loads YueScript code from a file into a function and immediately executes it. Overloads allow specifying an environment table and compiler configuration.

```APIDOC
dofile: function(filename: string, env: table, config?: Config): any...
  Parameters:
    filename: string - The file name.
    env: table - The environment table.
    config: Config - [Optional] The compiler options.
  Returns:
    any... - The return values of the loaded function.

dofile: function(filename: string, config?: Config): any...
  Parameters:
    filename: string - The file name.
    config: Config - [Optional] The compiler options.
  Returns:
    any... - The return values of the loaded function.
```

--------------------------------

### Continue Statement - With Loop Expressions for Filtering

Source: https://yuescript.org/doc/index

Demonstrates how 'continue' can be used with loop expressions to prevent specific iterations from being accumulated into the result table, effectively filtering the output. The example filters an array to include only even numbers.

```Yuescript
my_numbers = [1, 2, 3, 4, 5, 6]
odds = for x in *my_numbers
  continue if x % 2 == 1
  x
```

--------------------------------

### Define a basic class with constructor and methods in YueScript

Source: https://yuescript.org/doc/index

Demonstrates the fundamental syntax for defining a class in YueScript. It includes a constructor (`new`) to initialize instance properties and a method (`add_item`) to manipulate them. The `@` prefix is used as shorthand for `self.` to access instance variables.

```YueScript
class Inventory
  new: =>
    @items = {}

  add_item: (name) =>
    if @items[name]
      @items[name] += 1
    else
      @items[name] = 1
```

--------------------------------

### Exporting and Importing Macros in YueScript

Source: https://yuescript.org/doc/index

Demonstrates how to define and export macros from one YueScript file (`utils.yue`) and then import and use them in another (`main.yue`). It showcases symbol import, renaming, and piping with custom macros for functional programming patterns.

```YueScript
-- file: utils.yue
export macro map = (items, action) -> "[#{action} for _ in *#{items}]"
export macro filter = (items, action) -> "[_ for _ in *#{items} when #{action}]"
export macro foreach = (items, action) -> "for _ in *#{items}
  #{action}"

-- file main.yue
import "utils" as {
  $, -- symbol to import all macros
  $foreach: $each -- rename macro $foreach to $each
}
[1, 2, 3] |> $map(_ * 2) |> $filter(_ > 4) |> $each print _
```

--------------------------------

### Load YueScript Code from File

Source: https://yuescript.org/doc/index

Loads YueScript code from a file into a function. Overloads allow specifying an environment table and compiler configuration.

```APIDOC
loadfile: function(filename: string, env: table, config?: Config):
    nil | function(...: any): (any...),
    string | nil
  Parameters:
    filename: string - The file name.
    env: table - The environment table.
    config: Config - [Optional] The compiler options.
  Returns:
    function | nil - The loaded function, or nil if the loading failed.
    string | nil - The error message, or nil if the loading succeeded.

loadfile: function(filename: string, config?: Config):
    nil | function(...: any): (any...),
    string | nil
  Parameters:
    filename: string - The file name.
    config: Config - [Optional] The compiler options.
  Returns:
    function | nil - The loaded function, or nil if the loading failed.
    string | nil - The error message, or nil if the loading succeeded.
```

--------------------------------

### Yuescript Module Import Syntax

Source: https://yuescript.org/doc/index

Demonstrates various ways to import modules and specific items in Yuescript. This includes table destructuring for specific functions, implicit requiring of modules, Python-style imports, and aliasing for modules or destructured items.

```Yuescript
-- used as table destructuring
do
  import insert, concat from table
  -- report error when assigning to insert, concat
  import C, Ct, Cmt from require "lpeg"
  -- shortcut for implicit requiring
  import x, y, z from 'mymodule'
  -- import with Python style
  from 'module' import a, b, c

-- shortcut for requring a module
do
  import 'module'
  import 'module_x'
  import "d-a-s-h-e-s"
  import "module.part"

-- requring module with aliasing or table destructuring
do
  import "player" as PlayerModule
  import "lpeg" as :C, :Ct, :Cmt
  import "export" as {one, two, Something:{umm:{ch}}}
```

--------------------------------

### Yuescript Explicit Local Variable Declaration

Source: https://yuescript.org/doc/index

Explains how to explicitly declare local variables in Yuescript. This includes using `local *` to forward declare all variables within a `do` block as locals, and `local ^` to forward declare only variables starting with an uppercase letter as locals.

```Yuescript
do
  local a = 1
  local *
  print "forward declare all variables as locals"
  x = -> 1 + y + z
  y, z = 2, 3
  global instance = Item\new!

do
  local X = 1
  local ^
  print "only forward declare upper case variables"
  a = 1
  B = 2
```

--------------------------------

### For Loop - Shorter Single-Line Syntax

Source: https://yuescript.org/doc/index

Illustrates the concise single-line syntax for 'for' loops using the 'do' keyword, applicable to all loop variations when the body consists of a single statement.

```Yuescript
for item in *items do print item

for j = 1, 10, 3 do print j
```

--------------------------------

### For Loop - Basic Numeric and Generic Iteration

Source: https://yuescript.org/doc/index

Demonstrates the two primary forms of 'for' loops in Yuescript: numeric iteration with an optional step, and generic iteration over key-value pairs of an object.

```Yuescript
for i = 10, 20
  print i

for k = 1, 15, 2 -- an optional step provided
  print k

for key, value in pairs object
  print key, value
```

--------------------------------

### Preventing Destructive Assignment with 'using nil' in YueScript

Source: https://yuescript.org/doc/index

This YueScript example demonstrates the use of '(using nil)' in a function definition. It shows how 'using nil' prevents a function from overwriting variables from its enclosing scope, instead creating a new local variable if an assignment with the same name occurs.

```YueScript
i = 100

my_func = (using nil) ->
  i = "hello" -- a new local variable is created here

my_func!
print i -- prints 100, i is unaffected
```

--------------------------------

### Yuescript Function Definition with Arguments

Source: https://yuescript.org/doc/index

Shows how to define functions in Yuescript that accept arguments. Arguments are listed in parentheses before the '->' arrow, allowing the function to operate on provided inputs.

```Yuescript
sum = (x, y) -> print "sum", x + y
```

--------------------------------

### Multiline Function Chaining in YueScript

Source: https://yuescript.org/doc/index

Demonstrates how to write multi-line chained function calls in YueScript. It highlights the importance of consistent indentation for readability and correct parsing, allowing complex operations to be expressed clearly.

```YueScript
Rx.Observable
  .fromRange 1, 8
  \filter (x) -> x % 2 == 0
  \concat Rx.Observable.of 'who do we appreciate'
  \map (value) -> value .. '!'
  \subscribe print
```

--------------------------------

### Illustrate shared mutable class property issue in YueScript

Source: https://yuescript.org/doc/index

Highlights a common pitfall in OOP where mutable properties declared directly within a class are shared across all instances. This example demonstrates how modifications to such a property in one instance can unintentionally affect other instances, leading to unexpected behavior.

```YueScript
class Person
  clothes: []
  give_item: (name) =>
    table.insert @clothes, name

a = Person!
b = Person!

a\give_item "pants"
b\give_item "shirt"

-- will print both pants and shirt
print item for item in *a.clothes
```

--------------------------------

### Yuescript List Comprehension: Doubling Values

Source: https://yuescript.org/doc/index

Demonstrates a basic list comprehension in Yuescript to create a new list where each element from the original list is doubled. It iterates using `ipairs` for numeric indexing.

```Yuescript
items = [ 1, 2, 3, 4 ]
doubled = [item * 2 for i, item in ipairs items]
```

--------------------------------

### Define a function with default arguments in Yuescript

Source: https://yuescript.org/doc/index

Illustrates how to provide default values for function arguments in Yuescript. Any `nil` arguments are replaced by their defaults before the function body executes, ensuring arguments always have a value.

```Yuescript
my_function = (name = "something", height = 100) ->
  print "Hello I am", name
  print "My height is", height
```

--------------------------------

### Yuescript Table Comprehension: Unpacking Tuples into Key-Value Pairs

Source: https://yuescript.org/doc/index

Illustrates converting a list of two-element tuples into a table, where each tuple's first element becomes the key and the second becomes the value, using `unpack`.

```Yuescript
tuples = [ ["hello", "world"], ["foo", "bar"]]
tbl = {unpack tuple for tuple in *tuples}
```

--------------------------------

### Correctly initialize mutable instance properties in YueScript

Source: https://yuescript.org/doc/index

Provides the recommended approach for handling mutable instance state in YueScript classes. By initializing mutable properties within the class's constructor (`new`), each instance receives its own independent copy, preventing unintended side effects from shared state.

```YueScript
class Person
  new: =>
    @clothes = []
```

--------------------------------

### Load YueScript Code from String

Source: https://yuescript.org/doc/index

Loads YueScript code from a string into a function. Multiple overloads are available to specify chunk name, environment table, and compiler configuration.

```APIDOC
loadstring: function(input: string, chunkname: string, env: table, config?: Config):
    --[[loaded function]] nil | function(...: any): (any...),
    --[[error]] string | nil
  Parameters:
    input: string - The YueScript code.
    chunkname: string - The name of the code chunk.
    env: table - The environment table.
    config: Config - [Optional] The compiler options.
  Returns:
    function | nil - The loaded function, or nil if the loading failed.
    string | nil - The error message, or nil if the loading succeeded.

loadstring: function(input: string, chunkname: string, config?: Config):
    --[[loaded function]] nil | function(...: any): (any...),
    --[[error]] string | nil
  Parameters:
    input: string - The YueScript code.
    chunkname: string - The name of the code chunk.
    config: Config - [Optional] The compiler options.
  Returns:
    function | nil - The loaded function, or nil if the loading failed.
    string | nil - The error message, or nil if the loading succeeded.

loadstring: function(input: string, config?: Config):
    --[[loaded function]] nil | function(...: any): (any...),
    --[[error]] string | nil
  Parameters:
    input: string - The YueScript code.
    config: Config - [Optional] The compiler options.
  Returns:
    function | nil - The loaded function, or nil if the loading failed.
    string | nil - The error message, or nil if the loading succeeded.
```

--------------------------------

### YueScript Library Core API

Source: https://yuescript.org/doc/index

The core API for the YueScript language library, accessible via 'require("yue")'. It provides functionalities for versioning, file system interaction, code compilation, and loader management.

```APIDOC
yue: The YueScript language library.

version: string
  Description: The YueScript version.

dirsep: string
  Description: The file separator for the current platform.

yue_compiled: {string: string}
  Description: The compiled module code cache.

to_lua: function(code: string, config?: Config):
    --[[codes]] string | nil,
    --[[error]] string | nil,
    --[[globals]] {{string, integer, integer}} | nil
  Description: The YueScript compiling function. It compiles the YueScript code to Lua code.
  Parameters:
    code (string): The YueScript code.
    config (Config, optional): The compiler options.
  Returns:
    string | nil: The compiled Lua code, or nil if the compilation failed.
    string | nil: The error message, or nil if the compilation succeeded.
    {{string, integer, integer}} | nil: The global variables appearing in the code (with name, row and column), or nil if the compiler option `lint_global` is false.

file_exist: function(filename: string): boolean
  Description: The source file existence checking function. Can be overridden to customize the behavior.
  Parameters:
    filename (string): The file name.
  Returns:
    boolean: Whether the file exists.

read_file: function(filename: string): string
  Description: The source file reading function. Can be overridden to customize the behavior.
  Parameters:
    filename (string): The file name.
  Returns:
    string: The file content.

insert_loader: function(pos?: integer): boolean
  Description: Insert the YueScript loader to the package loaders (searchers).
  Parameters:
    pos (integer, optional): The position to insert the loader. Default is 3.
  Returns:
    boolean: Whether the loader is inserted successfully. It will fail if the loader is already inserted.
```

--------------------------------

### Yuescript Table Comprehension: Filtering Keys

Source: https://yuescript.org/doc/index

Demonstrates filtering key-value pairs in a table comprehension using a `when` clause, allowing specific keys to be excluded from the new table.

```Yuescript
no_color = {k, v for k, v in pairs thing when k != "color"}
```

--------------------------------

### Yuescript Function Call Chaining and Argument Application

Source: https://yuescript.org/doc/index

Illustrates how arguments are applied to the closest function when chaining multiple function calls in Yuescript. It highlights potential ambiguities and the need for explicit parentheses in complex expressions.

```Yuescript
sum 10, 20
print sum 10, 20

a b c "a", "b", "c"
```

--------------------------------

### Yuescript Switch with Single-Line When Blocks using 'then'

Source: https://yuescript.org/doc/index

Shows how to write compact 'when' and 'else' blocks in a Yuescript switch statement by utilizing the 'then' keyword for single-line 'when' clauses. This approach reduces verbosity for simple actions or return values.

```Yuescript
msg = switch math.random(1, 5)
  when 1 then "you are lucky"
  when 2 then "you are almost lucky"
  else "not so lucky"

```

--------------------------------

### Matching Array Elements in Yuescript Switch Statements

Source: https://yuescript.org/doc/index

Explains how to match against specific array elements and patterns within a `switch when` statement. It demonstrates capturing individual elements and assigning default values to captured variables if the element is not present.

```Yuescript
switch tb
  when [1, 2, 3]
    print "1, 2, 3"
  when [1, b, 3]
    print "1, #{b}, 3"
  when [1, 2, b = 3] -- b has a default value
    print "1, 2, #{b}"
```

--------------------------------

### Yuescript Table Comprehension: Generating Key-Value Pairs with `*`

Source: https://yuescript.org/doc/index

Shows how the `*` operator can be used in table comprehensions to iterate over a list of values and generate key-value pairs, such as creating a lookup table for square roots.

```Yuescript
numbers = [1, 2, 3, 4]
sqrts = {i, math.sqrt i for i in *numbers}
```

--------------------------------

### Commenting Syntax and Usage in YueScript

Source: https://yuescript.org/doc/index

Illustrates single-line (`--`) and multi-line (`--[[ ... ]]--`) comment syntax in YueScript. It also shows how comments can be embedded within expressions for inline documentation or temporary disabling of code parts.

```YueScript
-- I am a comment

str = --[[
This is a multi-line comment.
It's OK.
]] strA \ -- comment 1
  .. strB \ -- comment 2
  .. strC

func --[[port]] 3000, --[[ip]] "192.168.1.1"
```

--------------------------------

### Yuescript Basic Function Definition

Source: https://yuescript.org/doc/index

Introduces the fundamental syntax for defining functions in Yuescript using the '->' arrow operator. It shows how to declare an empty function and subsequently call it.

```Yuescript
my_function = ->
my_function() -- call the empty function
```

--------------------------------

### Yuescript Direct Export to Module Table

Source: https://yuescript.org/doc/index

Demonstrates how to directly add items to the exported module table without creating corresponding local variables. This is useful for exporting properties using dot notation or bracket notation for dynamic keys.

```Yuescript
export.itemA = tb
export.<index> = items
export["a-b-c"] = 123
```

--------------------------------

### Conditional Logic in Yuescript Functions and Assignments

Source: https://yuescript.org/doc/index

Explains how `if` statements can be integrated into function definitions and used for assigning values to variables. This demonstrates the flexibility of conditionals in Yuescript for building dynamic logic.

```Yuescript
is_tall = (name) ->
  if name == "Rob"
    true
  else
    false

message = if is_tall "Rob"
  "I am very tall"
else
  "I am not so tall"

print message -- prints: I am very tall
```

--------------------------------

### Repeat Loop - Basic Usage

Source: https://yuescript.org/doc/index

Shows the 'repeat...until' loop construct, which executes its body at least once and continues iterating until the specified condition becomes true.

```Yuescript
i = 10
repeat
  print i
  i -= 1
until i == 0
```

--------------------------------

### Perform Class Mixing with 'using' Keyword in Yuescript

Source: https://yuescript.org/doc/index

Explains Yuescript's 'using' keyword for class mixing, which allows incorporating functions from plain tables or existing class objects into a new class. It also highlights considerations for overriding the '__index' metamethod when mixing with tables.

```Yuescript
MyIndex = __index: var: 1

class X using MyIndex
  func: =>
    print 123

x = X!
print x.var

class Y using X

y = Y!
y\func!

assert y.__class.__parent ~= X -- X is not parent of Y
```

--------------------------------

### YueScript Compiler Configuration Options

Source: https://yuescript.org/doc/index

Defines the various options available for configuring the YueScript compiler, including settings for global variable linting. These options control aspects of the compilation process.

```APIDOC
Config:
  - Description: The compiler compile options.
  - Fields:
    - lint_global: boolean
      - Description: Whether the compiler should collect the global variables appearing in the code.
```

--------------------------------

### Define Basic Yuescript Backcall

Source: https://yuescript.org/doc/index

Demonstrates the fundamental syntax for defining a backcall in Yuescript using the `<-` arrow. This construct un-nests callbacks by implicitly filling in a function call as the last parameter. The compiled Lua output is also shown.

```Yuescript
<- f
print "hello"
```

```Lua
<- f
print "hello"
```

--------------------------------

### Programmatic YueScript to Lua Compilation with `yue.to_lua`

Source: https://yuescript.org/doc/index

Shows how to use the `yue.to_lua` function to compile YueScript code strings into Lua code directly within a Lua environment. It highlights various compilation options such as implicit return roots, line number preservation, global linting, and target Lua version.

```Lua
local yue = require("yue")
local codes, err, globals = yue.to_lua([[
f = ->
  print "hello world"
f!
]],{
  implicit_return_root = true,
  reserve_line_number = true,
  lint_global = true,
  space_over_tab = false,
  options = {
    target = "5.4",
    path = "/script"
  }
})
```

--------------------------------

### Yuescript List Slicing: Specifying Minimum and Maximum Bounds

Source: https://yuescript.org/doc/index

Explains how to use slicing with the `*` operator to extract a sub-list based on explicit minimum and maximum index bounds, inclusive of both.

```Yuescript
slice = [item for item in *items[1, 5]]
```

--------------------------------

### Advanced YueScript Module Loading with Custom Error Tracing

Source: https://yuescript.org/doc/index

Illustrates a more controlled approach to loading YueScript modules in Lua. It involves manually inserting the YueScript loader and using `xpcall` to catch errors, providing a custom traceback function (`yue.traceback`) for detailed debugging.

```Lua
local yue = require("yue")
yue.insert_loader()
local success, result = xpcall(function()
  return require("yuescript_module_name")
end, function(err)
  return yue.traceback(err)
end)
```

--------------------------------

### Yuescript List Slicing: Omitting Minimum Bound and Using Step

Source: https://yuescript.org/doc/index

Shows how to slice a list by omitting the minimum bound (defaults to 1) and specifying a step size, allowing extraction of elements at regular intervals (e.g., odd-indexed items).

```Yuescript
slice = [item for item in *items[,,2]]
```

--------------------------------

### Yuescript List Comprehension: Nested Loops for Cartesian Product

Source: https://yuescript.org/doc/index

Demonstrates how to use multiple `for` clauses in a list comprehension to achieve nested loop behavior, effectively generating a Cartesian product of two lists.

```Yuescript
x_coords = [4, 5, 6, 7]
y_coords = [9, 2, 3]

points = [ [x, y] for x in *x_coords \
for y in *y_coords]
```

--------------------------------

### Yuescript Chaining Assignment

Source: https://yuescript.org/doc/index

Shows how to perform chaining assignments in Yuescript, allowing multiple variables to be assigned the same value in a single statement. This is a concise way to initialize several variables to an identical value or the result of a function call.

```Yuescript
a = b = c = d = e = 0
x = y = z = f!
```

--------------------------------

### Yuescript List Slicing: Reversing Order with Negative Step

Source: https://yuescript.org/doc/index

Demonstrates using a negative step size in slicing to iterate and extract elements in reverse order from a specified range.

```Yuescript
reverse_slice = [item for item in *items[-1,1,-1]]
```

--------------------------------

### For Loop as a Line Decorator in Yuescript

Source: https://yuescript.org/doc/index

Shows how `for` loops can be concisely applied as line decorators for iterating over collections. This compact syntax is useful for simple loop bodies.

```Yuescript
print "item: ", item for item in *items
```

--------------------------------

### Chaining Comparison Operators in YueScript

Source: https://yuescript.org/doc/index

Illustrates how comparison operators can be arbitrarily chained in YueScript, allowing for concise and readable expressions. This feature simplifies complex conditional logic by combining multiple comparisons into a single line.

```YueScript
print 1 < 2 <= 2 < 3 == 3 > 2 >= 1 == 1 < 3 != 5
-- output: true

a = 5
print 1 <= a <= 10
-- output: true
```

--------------------------------

### Use Yuescript Backcalls with `do` Statement for Sequential Operations

Source: https://yuescript.org/doc/index

Demonstrates how to use a `do` statement to group multiple asynchronous operations involving backcalls. This allows for sequential execution of operations and enables further code to execute after the backcall sequence, improving control flow for chained operations.

```Yuescript
result, msg = do
  data <- readAsync "filename.txt"
  print data
  info <- processAsync data
  check info
print result, msg
```

```Lua
result, msg = do
  data <- readAsync "filename.txt"
  print data
  info <- processAsync data
  check info
print result, msg
```

--------------------------------

### Basic Array Destructuring in Yuescript

Source: https://yuescript.org/doc/index

Illustrates how to unpack values from an array-like table into individual variables based on their position using destructuring assignment.

```Yuescript
thing = [1, 2]

[a, b] = thing
print a, b
```

--------------------------------

### Basic Yuescript Switch Statement with Assignment

Source: https://yuescript.org/doc/index

Demonstrates the fundamental structure of a Yuescript switch statement, including an assignment expression within the switch condition, multiple 'when' clauses for matching against several values, and an 'else' block for unmatched cases. Comparison is performed using the '==' operator.

```Yuescript
switch name := "Dan"
  when "Robert"
    print "You are Robert"
  when "Dan", "Daniel"
    print "Your name, it's Dan"
  else
    print "I don't know about you with name #{name}"

```

--------------------------------

### While and Until Loops as Line Decorators in Yuescript

Source: https://yuescript.org/doc/index

Demonstrates the use of `while` and `until` loops as line decorators for compact conditional looping. `while` continues as long as the condition is true, and `until` continues until the condition becomes true.

```Yuescript
game\update! while game\isRunning!

reader\parse_line! until reader\eof!
```

--------------------------------

### Demonstrate nested multi-line function arguments in Yuescript

Source: https://yuescript.org/doc/index

Illustrates how multi-line function invocations can be nested in Yuescript. The level of indentation is crucial for the parser to determine to which function the arguments belong, maintaining clarity in complex calls.

```Yuescript
my_func 5, 6, 7,
  6, another_func 6, 7, 8,
    9, 1, 2,
  5, 4
```

--------------------------------

### Error Handling with Try-Catch Blocks in YueScript

Source: https://yuescript.org/doc/index

Details the `try-catch` syntax for robust error handling in YueScript. It covers capturing errors, returning success/result pairs, and integrating `try` blocks with `if` assignment patterns for conditional execution based on operation outcome.

```YueScript
try
  func 1, 2, 3
catch err
  print yue.traceback err

success, result = try
  func 1, 2, 3
catch err
  yue.traceback err

try func 1, 2, 3
catch err
  print yue.traceback err

success, result = try func 1, 2, 3

try
  print "trying"
  func 1, 2, 3

-- working with if assignment pattern
if success, result := try func 1, 2, 3
catch err
    print yue.traceback err
  print result
```

--------------------------------

### Yuescript Explicit Function Return

Source: https://yuescript.org/doc/index

Shows how to use the 'return' keyword in Yuescript functions for explicit control over what value is returned, overriding the implicit return behavior.

```Yuescript
sum = (x, y) -> return x + y
```
Tokens:
Raw