inline for and Unrolled Loops
Iterate at compile time.
inline for and Unrolled Loops is a free Zig Academy lesson on CoddyKit — lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Zig Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
A Loop That Runs at Compile-Time
An inline for is a loop the compiler unrolls during compilation. Instead of looping at run-time, it copies the body for each item. 🔁
The inline Keyword
Put inline in front of for to ask Zig to expand the loop at compile-time. The iteration count must be known then.
inline for (items) |item| {}Unrolling Means Copying the Body
Unrolling replaces the loop with one copy of its body per element. There is no loop counter left at run-time, just straight-line code.
Iterate a Known Tuple
A common use is walking a tuple whose fields differ in type. Each unrolled copy can treat its element with the right type.
inline for (.{ 1, true, 3.0 }) |v| {}The Index Can Be comptime
With an inline for the loop index is a compile-time value on each pass, so you can use it where only constants are allowed.
inline for (list, 0..) |v, i| {}Each Iteration Can Differ
Since the body is duplicated, every copy can use a different type or value. A normal for loop cannot do that.
Reflect Over Struct Fields
Pair inline for with type reflection to visit each field of a struct at compile-time, generating tailored code for every one.
inline for (fields) |field| {}Trade Code Size for Speed
Unrolling removes loop overhead but grows the binary. Use inline for on small, fixed counts where the speedup is worth it.
The Count Must Be Known
An inline for needs a length the compiler can see. Looping a run-time slice of unknown length cannot be unrolled.
There Is Also inline while
Zig offers inline while too. It unrolls a while loop at compile-time when the condition can be resolved during compilation.
Keep It to Small Counts
Reach for inline for when the item count is small and fixed. For large or unknown lengths, a plain for loop keeps the binary lean.
Quick Check
What does adding inline to a for loop ask the Zig compiler to do?
Recap
An inline for unrolls a known-length loop at compile-time, letting each copy use its own type and removing run-time loop overhead. 🎯
Frequently asked questions
Is the “inline for and Unrolled Loops” lesson free?
Yes — the full text of “inline for and Unrolled Loops” is free to read here on the web, and the Zig Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Zig Academy course, upgrade to CoddyKit PRO.
What will I learn in “inline for and Unrolled Loops”?
Iterate at compile time. You practise Zig Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Zig Academy?
No prior experience is required. Zig Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 4 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “inline for and Unrolled Loops” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Zig Academy lesson?
Yes. Every Zig Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Compile-Time vs Run-Time
- comptime Parameters and Values
- Types Are comptime Values
- inline for and Unrolled Loops