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Foundations
Local variables Global variables Nil Booleans Numbers Strings Multiple assignment Comments
Control Flow
If elseif While loop Repeat until Numeric for Generic for Break Goto labels Do blocks
Functions
Function definitions Local functions Multiple returns Varargs First-class functions Closures Tail calls Self parameter colon syntax
Tables
Table literals Array-style tables Key-value tables Mixed tables Table.insert Table.remove Table.concat Table.sort
Metatables
Setmetatable __index __newindex __tostring __add __eq __len Rawget rawset
Iterators and Coroutines
Pairs Ipairs Next Custom iterator Coroutine.create Coroutine.resume Coroutine.yield Coroutine.wrap
Modules and Environments
Require Package.path Module return table Local module state _ENV Load Loadfile Dofile
Strings and Patterns
String.find String.match String.gmatch String.gsub Pattern classes Captures Frontier patterns Balanced patterns
Files and Errors
Io.open File read File write Io.lines Error Assert Pcall Xpcall
Advanced Lua
Weak tables Garbage collection Table.pack unpack Utf8 library Os.date Math.random Debug traceback C API concept
Lua / Control Flow

Generic for

Learn generic for in Lua through a focused explanation, a dedicated topic-specific example, an engineering boundary, and a mastery check.

10 min read • Beginner

generic for is an atomic Lua topic inside Control Flow. The example uses the named construct directly so you can see its syntax, data flow, and observable behavior.

Read the code by locating the exact feature named generic for, then trace the value before and after that feature runs. This lesson is intentionally isolated from neighboring topics: changing identifiers alone would not reproduce the same behavior because the construct itself is different.

Topic-specific example

lua-0013-fadc93cec3.lua
lua Try It Live 
local function iter(t) local k=nil; return function() k=next(t,k); if k then return k,t[k] end end end
for k,v in iter({a=1,b=2}) do print(k,v) end
Edge case / engineering note

For generic for, test the boundary that makes the feature meaningful: invalid input, an empty value, a missing branch, lifecycle/cleanup, or a type/runtime constraint. Do not infer correctness only from the happy path.

Content source & attribution
Original Syntaxis Content · Original Syntaxis Content

Lesson quizzes

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