intro-to-zig-talk/talk.md

## Intro

Before we start:
- might be running slow - streaming + old laptop
- no slides, just text
- live coding demo
- will try to cover most cool things
    - but no multithreading/async/atomics and C interop details in talk

Who am I?:
- Ivan Notaroš - nothke
- indie gamedev for 10+ years
- studied architecture
- started by modding - 3D modeling
- Unity, C# since ~2013
- many game jams: https://nothke.itch.io/
- Unity had too many limitations, esp for procgen, progressively went lower level
- custom engine in C++ since 2020
    - making a rally game: Shakedown Rally in it
- heard of Zig a few years ago
    - kept hearing of cooler and cooler features
    - started making an engine just to see how easy it would be to move C++ to Zig
- I stream gamedev on twitch too: https://twitch.tv/nothke
- Windows user all my life 😢

## Zig
- Hard to put in an elevator pitch
- Fell in love with language and community - https://ziglang.org
- Don't know where to start, I'll try my best

Zig (language) facts:
- Zig is an imperative,
- structured,
- general-purpose,
- statically typed,
- compiled,
- system programming language

History:
- designed by Andrew Kelley
    - https://andrewkelley.me
- first version (0.1) since 2016
- currently at 0.14 dev, 0.13.0 stable
- since 0.10 - self-hosted
- since 2020, Zig software foundation: https://ziglang.org/news/announcing-zig-software-foundation/

Goals:
- "better C"
- simple, clear, readable
- very explicit
- maintainable
- robust
- sane defaults
- fast: runtime AND compile
- no hidden allocations
- write all in Zig
- minimal dependencies
- no UB in debug or safe
- unambigous, context-free syntax
- one obvious way to do things

Some really cool bits (apart from already mentioned):
- all-in-one cross-compiling toolchain
- include and seamlessly interoperate with C code
- comptime - powerful metaprogramming - written in zig
- integrated build system - written in zig
- no hidden allocations - easy to reason about memory
- amazing standard library
    - which is completely comprehensible! (unlike C++ STL 😛)
- decentralized package manager
- zls
- pointer disambiguation
- no exceptions - error types
- no header files (!!!)
- bit-packing types
- SIMD vectors
- no function or operator overloads
- strong formatting convention
- OOP-lite
- no macros
- if it looks like a function, its a function. Fields are just fields!

### The toolchain
- all-in-one
- cross compile from-to any system
- compile C and C++
- include C code
    - translate-c - C to zig
    - -ofmt=c - zig to C
- very fast
- build system written in Zig
    - just `zig build run`
    - no CMake!
- integrated tests
- 4 compiler modes `--release=[mode]` :
    - debug
    - safe
    - fast
    - small
- lazy compiler
    - only compiles what you use

## Live demo!

### installing
- with VSCode:
    - install Zig extension
    - ctrl+shift+P
        - install zig
        - install zls
- alternatively:
    - with zvm https://www.zvm.app/
        - `zvm i --zls master` or `0.13.0` (for now)
    - install binary
        - build zls
    - sudo apt install zig

### Language walkthrough

const and var
- `: T =`
- initialization
- `const` - immutable
    - const resolved at compile time if it can be
    - can act as an alias to types
- `var` - mutable

integers
- unsigned: `u8`, `u16`, `u32`..
- signed: `i8`, `u16`, `u32`..
- but also arbitrary width: `i2`, `u6`, `i31`..
- casting - peer type resolution
    - narrow to wide - allowed
    - wide to narrow - disallowed, must be explicit @intCast
        - if compile-time known - casting checked at compile time
- overflow is an error
    - but explicit overflow operator `+%`, `-%`
- Note: `const a = 1;` is a `comptime_int`

- floats `f16`, `f32`, `f64`, `f128` and `f80`

pointers (single item):
- `*T`
- `&` - address of operator
- can't be null
- (..we'll come back to more pointers..)

`[N]T` - arrays
- on stack, compile-time known size
    - size part of type
- `[3]T`
- `[_]T` - inferred size from initialization
- unambiguously values
    - unlike C which pretend to be pointers

`[]T` - slices
- `const slice: []T = &arr;`
- or `const slice = arr[0..];`

strings
- what strings..? They're just `[]u8`
- "string class" not needed, `std.mem.-` functions are rich enough for every need
- For unicode there's `std.unicode.-`

`++` `**` - compile-time array operators
- `arr ++ arr2` - concatenates
- `arr ** 3` - repeats

structs
- `const MyStruct = struct {}`
- fields
    - always public
    - rearranged to better fit memory
        - unless `extern`
    - can be default initialized
- are namespaces
- namespaced functions
    - if first parameter is `MyStruct`, acts as a "method"
    - if self needs to mutate, pass as pointer `self: *MyStruct`
- initialization
    - uninitialized fields not allowed
        - (but fields can be default initialized ^)
    - force uninitialized with `= undefined`
        - explicitely shoot yourself in the foot! (unlike C)
- files are structs too!
- `packed`
    - bools become 1 bits
    - arbitrary-sized ints become bit-sized
- no ctors/dtors - more on that later..

enums and unions
- enums
- (bare) unions
    - known which type
    - no type punning
- tagged unions
    - use a backing enum
    - switch
    - polymorphism on stack!
- ^ enums and unions also act as namespaces that can have functions! 😉

Zig has no operator overloads!
- = is always a (shallow) copy
- [] only works on arrays, slices and multi-item pointers
- & always a pointer to - looking at C++

But I'm a gamedev and really need my vector arithmetic overloads 😭
- Don't worry! There are built-in Vectors! 😍

`@Vector(3, i32)`
- SIMD out of the box
- can index
- cannot loop through
    - but can cast into compatible array `[3]f32 = @Vector(3, f32)`

functions
- `fn`
- parameters always const
    - compiler can infer copy or const-ref, depending on size
    - params
- return must be known
    - but comptime expressions possible
- function pointers

control flow
- `if (bool)`
- `while (bool)`
- `for (array) |x| {}`
    - `|x|` capture bars
        - expression creates variable
    - range `0..`
    - multi-item
    - inline - unrolls loops
- switch
    - exhaustive

!?
- `!T` errors and `?T` optionals
- ! error unions
    - error enum
    - type example: divide by zero
    - handling errors:
        - try
        - catch
        - switch
- ? optionals
    - can be `null`
    - `?*T` - nullable pointers
        - don't consume extra space
    - `opt.?` unwraps value, if null throws error
    - `opt orelse 0` if null use another value
    - `if (opt) |value| {}` if not null, unwraps
    - `while (opt) |value| {}` runs until null
        - can be used to implement iterators `while (iter.next()) ..`

### Disambiguation of Pointers
- in C/C++, a pointer can be
    - dereferenced `*ptr`
    - indexed `ptr[3]` - and not bounds checked
    - added to `ptr + 1`
    - `nullptr`
    - not known if it points to a null terminated string..? 🤷‍♂️

- Zig disambiguates all these and puts them in separate types:
    - `*T` - single-item pointer - cannot be indexed
    - `[]T` - slice - bounded, cannot be dereferenced with t.*
    - `[*]T` - multi-item pointer - unbounded
    - `[:0]` - sentinel-terminated, 0 in this case
    - `?*T` `?[]T` - nullable
    - `*anyopaque` - equivalent to void*
    - `*align(1:0:1) T` - pointers can also hold alignment and bit offset in their type
    - `[*c]` - can do all - but use it only for interoperating with C code!
    
- Why? intent is much clearer!

### Comptime
- no macros, no templates, no constexpr
- call any function at compile time!
- types are types
    - (at compile time only)
    - can be used to return types to create generics
        - example: Optional(T)
- full static reflection
    - e.g. looping through fields
        - https://gist.github.com/travisstaloch/71a7a2bc260997abe06016c619b40bf2
- `anytype`
    - function parameter type that can ONLY be inferred at compile-time
    - similar to template function `auto` parameters in C++
- `comptime var`
    - can be mutated but only at compile-time
    - acts as const at runtime

## Memory Management

Memory management in other languages:
- manual (C) - malloc() free()
- RAII (C++)
- GC (Java/C#/python/Go)
- compile time resolved (rust)

Zig - manual, BUT, unlike C:
- `defer`
    - executes at the end of the scope
    - like RAII - BUT controlled by the user
    - `errdefer` like defer but only when error is thrown
- has allocators

### Allocators
- interface used in std with anything that allocates heap memory
- PageAllocator 
    - the "dumb" one
    - makes syscalls
- FixedBufferAllocator
    - provide a buffer, can be on stack
    - not resizeable
- GeneralPurposeAllocator
    - can catch leaks in debug
- ArenaAllocator
    - can discard entire chunks
- TestingAllocator
    - only available in tests

- Demo how to use with `std.ArrayList`

## Built-in Tests
- `test "My Test" {}`
- `std.testing.expect-`
- just `zig build test`

## Package manager
- build.zig.zon
- not centralized
- hash to check code correctness
- `zig fetch --save "link"`

## Cons
- not 1.0 yet
    - changes from version to version
    - async not there yet
- C/C++ ecosystem is much older and versatile
- no built-in vtable-inheritance (dynamic dispatch)
    - but you can do your own in comptime
    - example (old): https://github.com/alexnask/interface.zig
- no lambdas
    - but https://github.com/ziglang/zig/issues/6965

## Community and Resources
- Online:
    - discord: https://discord.gg/invite/zig
    - ziggit: https://ziggit.dev/
    - Dude the Builder: https://www.youtube.com/@dudethebuilder/videos
- Offline:
    - Software you can love https://sycl.it/
    - meetups on zig

## Future of Zig
- goal of 0.14.0: super fast compile times
- getting rid of LLVM:
    - with LLVM 170MB, without 4.4

## Conclusions
- wHeRe dOeS zIg fIt iN tHe mOdeRn wOrLd??
    - Aren't you convinced by the talk..?
    - Reduces friction
- Companies already using Zig:
    - Tigerbeetle https://tigerbeetle.com/
    - Bun https://bun.sh/
    - Uber (build system)
- `zig zen`
- What about Odin, jai..?
- Will do the same talk in Hamburg for code.talks

Epilogue:
- Thanks! Now you can code in Zig⚡ !
- nothke: https://nothke.github.io/