Standard Lua Libraries

Standard Lua Libraries

Core Lua libraries automatically available in all Wippy processes. No require() needed.

Global Functions

Type and Conversion

type(value)         -- Returns: "nil", "number", "string", "boolean", "table", "function", "thread", "userdata"
tonumber(s [,base]) -- Convert to number, optional base (2-36)
tostring(value)     -- Convert to string, calls __tostring metamethod

Assertions and Errors

assert(v [,msg])    -- Raises error if v is false/nil, returns v otherwise
error(msg [,level]) -- Raises error at specified stack level (default 1)
pcall(fn, ...)      -- Protected call, returns ok, result_or_error
xpcall(fn, errh)    -- Protected call with error handler function

Table Iteration

pairs(t)            -- Iterate all key-value pairs
ipairs(t)           -- Iterate array portion (1, 2, 3, ...)
next(t [,index])    -- Get next key-value pair after index

Metatables

getmetatable(obj)       -- Get metatable (or __metatable field if protected)
setmetatable(t, mt)     -- Set metatable, returns t

Raw Table Access

Bypass metamethods for direct table access:

rawget(t, k)        -- Get t[k] without __index
rawset(t, k, v)     -- Set t[k]=v without __newindex
rawequal(a, b)      -- Compare without __eq

Utilities

select(index, ...)  -- Return args from index onwards
select("#", ...)    -- Return number of args
unpack(t [,i [,j]]) -- Return t[i] through t[j] as multiple values
print(...)          -- Print values (uses structured logging in Wippy)

Global Variables

_G        -- The global environment table
_VERSION  -- Lua version string

Table Manipulation

Functions for modifying tables:

table.insert(t, [pos,] value)  -- Insert value at pos (default: end)
table.remove(t [,pos])         -- Remove and return element at pos (default: last)
table.concat(t [,sep [,i [,j]]]) -- Concatenate array elements with separator
table.sort(t [,comp])          -- Sort in place, comp(a,b) returns true if a < b
table.unpack(t [,i [,j]])      -- Unpack table elements as multiple values

local items = {"a", "b", "c"}

table.insert(items, "d")           -- {"a", "b", "c", "d"}
table.insert(items, 2, "x")        -- {"a", "x", "b", "c", "d"}
table.remove(items, 2)             -- {"a", "b", "c", "d"}, returns "x"

local csv = table.concat(items, ",")  -- "a,b,c,d"

table.sort(items, function(a, b)
    return a > b  -- Descending order
end)

String Operations

String manipulation functions. Also available as methods on string values:

Pattern Matching

string.find(s, pattern [,init [,plain]])   -- Find pattern, returns start, end, captures
string.match(s, pattern [,init])           -- Extract matching substring
string.gmatch(s, pattern)                  -- Iterator over all matches
string.gsub(s, pattern, repl [,n])         -- Replace matches, returns string, count

Case Conversion

string.upper(s)   -- Convert to uppercase
string.lower(s)   -- Convert to lowercase

Substrings and Characters

string.sub(s, i [,j])      -- Substring from i to j (negative indexes from end)
string.len(s)              -- String length (or use #s)
string.byte(s [,i [,j]])   -- Numeric codes of characters
string.char(...)           -- Create string from character codes
string.rep(s, n)           -- Repeat string n times
string.reverse(s)          -- Reverse string

Formatting

string.format(fmt, ...)    -- Printf-style formatting

Format specifiers: %d (integer), %f (float), %s (string), %q (quoted), %x (hex), %o (octal), %e (scientific), %% (literal %)

local s = "Hello, World!"

-- Pattern matching
local start, stop = string.find(s, "World")  -- 8, 12
local word = string.match(s, "%w+")          -- "Hello"

-- Substitution
local new = string.gsub(s, "World", "Wippy") -- "Hello, Wippy!"

-- Method syntax
local upper = s:upper()                       -- "HELLO, WORLD!"
local part = s:sub(1, 5)                      -- "Hello"

Patterns

Pattern	Matches
.	Any character
%a	Letters
%d	Digits
%w	Alphanumeric
%s	Whitespace
%p	Punctuation
%c	Control characters
%x	Hexadecimal digits
%z	Zero (null)
[set]	Character class
[^set]	Negated class
*	0 or more (greedy)
+	1 or more (greedy)
-	0 or more (lazy)
?	0 or 1
^	Start of string
$	End of string
%b()	Balanced pair
(...)	Capture group

Uppercase versions (%A, %D, etc.) match the complement.

Math Functions

Mathematical functions and constants:

Constants {id=“math-constants”}

math.pi       -- 3.14159...
math.huge     -- Infinity
math.mininteger  -- Minimum integer
math.maxinteger  -- Maximum integer

Basic Operations

math.abs(x)           -- Absolute value
math.min(...)         -- Minimum of arguments
math.max(...)         -- Maximum of arguments
math.floor(x)         -- Round down
math.ceil(x)          -- Round up
math.modf(x)          -- Integer and fractional parts
math.fmod(x, y)       -- Floating-point remainder

Powers and Roots

math.sqrt(x)          -- Square root
math.pow(x, y)        -- x^y (or use x^y operator)
math.exp(x)           -- e^x
math.log(x)           -- Natural log
math.log10(x)         -- Base-10 log

Trigonometry

math.sin(x)   math.cos(x)   math.tan(x)    -- Radians
math.asin(x)  math.acos(x)  math.atan(x)
math.atan2(y, x)                            -- Arc tangent of y/x
math.sinh(x)  math.cosh(x)  math.tanh(x)   -- Hyperbolic
math.deg(r)   -- Radians to degrees
math.rad(d)   -- Degrees to radians

Random Numbers

math.random()         -- Random float [0,1)
math.random(n)        -- Random integer [1,n]
math.random(m, n)     -- Random integer [m,n]
math.randomseed(x)    -- Set random seed

Type Conversion

math.tointeger(x)     -- Convert to integer or nil
math.type(x)          -- "integer", "float", or nil
math.ult(m, n)        -- Unsigned less-than comparison

Coroutines

Coroutine creation and control. See Channels and Coroutines for channels and concurrent patterns:

coroutine.create(fn)        -- Create coroutine from function
coroutine.resume(co, ...)   -- Start/continue coroutine
coroutine.yield(...)        -- Suspend coroutine, return values to resume
coroutine.status(co)        -- "running", "suspended", "normal", "dead"
coroutine.running()         -- Current coroutine (nil if main thread)
coroutine.wrap(fn)          -- Create coroutine as callable function

Spawning Concurrent Coroutines

Spawn a concurrent coroutine that runs independently (Wippy-specific):

coroutine.spawn(fn)         -- Spawn function as concurrent coroutine

-- Spawn background task
coroutine.spawn(function()
    while true do
        check_health()
        time.sleep("30s")
    end
end)

-- Continue main execution immediately
process_request()

Error Handling

Structured error creation and classification. See Error Handling for full documentation:

Constants {id=“error-constants”}

errors.UNKNOWN           -- Unclassified error
errors.INVALID           -- Invalid argument or input
errors.NOT_FOUND         -- Resource not found
errors.ALREADY_EXISTS    -- Resource already exists
errors.PERMISSION_DENIED -- Permission denied
errors.TIMEOUT           -- Operation timed out
errors.CANCELED          -- Operation cancelled
errors.UNAVAILABLE       -- Service unavailable
errors.INTERNAL          -- Internal error
errors.CONFLICT          -- Conflict (e.g., concurrent modification)
errors.RATE_LIMITED      -- Rate limit exceeded

Functions {id=“error-functions”}

-- Create error from string
local err = errors.new("something went wrong")

-- Create error with metadata
local err = errors.new({
    message = "User not found",
    kind = errors.NOT_FOUND,
    retryable = false,
    details = {user_id = 123}
})

-- Wrap existing error with context
local wrapped = errors.wrap(err, "failed to load profile")

-- Check error kind
if errors.is(err, errors.NOT_FOUND) then
    -- handle not found
end

-- Get call stack from error
local stack = errors.call_stack(err)

Error Methods

err:message()    -- Get error message string
err:kind()       -- Get error kind (e.g., "NOT_FOUND")
err:retryable()  -- true, false, or nil (unknown)
err:details()    -- Get details table or nil
err:stack()      -- Get stack trace as string

Restricted Features

The following standard Lua features are NOT available for security:

Feature	Alternative
load, loadstring, loadfile, dofile	Use Dynamic Evaluation module
collectgarbage	Automatic GC
rawlen	Use # operator
io.*	Use File System module
os.execute, os.exit, os.remove, os.rename, os.tmpname	Use Command Execution, Environment modules
debug.*	Not available
utf8.*	Not available
package.loadlib	Native libraries not supported

See Also

• Channels and Coroutines - Go-style channels for concurrency
• Error Handling - Creating and handling structured errors
• OS Time - System time functions