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6 knowledge files: rust, SOLID/DRY, ast-grep, karpathy, golang, caveman 65 chunks ingested to log/knowledge/learn/latest.jsonl Chunks on ## headings, SHA256 dedup, configurable chunk size
64 lines
3.2 KiB
Markdown
64 lines
3.2 KiB
Markdown
# Rust Fundamentals
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## Ownership & Borrowing
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- Every value has exactly one owner. When owner goes out of scope, value is dropped.
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- `&T` immutable borrow, `&mut T` mutable borrow. Cannot have `&mut` while `&` exists.
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- Move semantics by default for non-Copy types. Clone for explicit deep copy.
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## Lifetimes
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- `'a` annotations tell compiler how long references live.
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- Elision rules: single input lifetime → applied to all outputs. `&self` → output gets `'self` lifetime.
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- `'static` means reference lives for entire program. String literals are `&'static str`.
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## Error Handling
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- `Result<T, E>` for recoverable errors, `panic!` for unrecoverable.
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- `?` operator propagates errors. Use `anyhow::Result` for application code, `thiserror` for library errors.
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- Never use `.unwrap()` in production — use `.expect("reason")` or proper error handling.
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## Traits & Generics
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- Traits define shared behavior: `trait Summary { fn summarize(&self) -> String; }`
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- Trait bounds: `fn notify(item: &impl Summary)` or `fn notify<T: Summary>(item: &T)`
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- `dyn Trait` for trait objects (dynamic dispatch), `impl Trait` for static dispatch.
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- Blanket implementations: `impl<T: Display> ToString for T`
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## Smart Pointers
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- `Box<T>` heap allocation with single ownership.
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- `Rc<T>` reference-counted shared ownership (single-threaded).
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- `Arc<T>` atomic reference-counted (thread-safe). Use with `Mutex<T>` or `RwLock<T>`.
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- `Cow<'a, T>` clone-on-write — borrows when possible, clones when mutation needed.
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## Concurrency
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- `Send` — type can be transferred across threads. `Sync` — type can be shared between threads.
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- `tokio::spawn` for async tasks. `rayon` for data parallelism.
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- Channels: `mpsc::channel()` for multi-producer single-consumer. `crossbeam` for advanced patterns.
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- `async/await` — futures are lazy, must be `.await`ed or spawned.
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## Pattern Matching
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- `match` is exhaustive — must cover all variants.
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- `if let Some(x) = option` for single-pattern matching.
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- Destructuring: `let (a, b) = tuple;` and `let Point { x, y } = point;`
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- Guards: `match x { n if n > 0 => ..., _ => ... }`
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## Module System
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- `mod foo;` loads from `foo.rs` or `foo/mod.rs`.
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- `pub(crate)` visible within crate only. `pub(super)` visible to parent module.
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- `use crate::module::Type` absolute path. `use super::Type` relative path.
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- Re-exports: `pub use inner::Type;` to flatten module hierarchy.
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## Iterators
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- `.iter()` borrows, `.into_iter()` consumes, `.iter_mut()` mutable borrow.
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- Lazy — nothing happens until consumed (`.collect()`, `.for_each()`, `.count()`).
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- Chaining: `.filter().map().flat_map().take().collect::<Vec<_>>()`
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- `impl Iterator for MyType { type Item = T; fn next(&mut self) -> Option<Self::Item> }`
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## Macros
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- `macro_rules!` for declarative macros. `#[derive(...)]` for derive macros.
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- `proc_macro` for procedural macros (attribute, derive, function-like).
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- `vec![1, 2, 3]` expands to `{ let mut v = Vec::new(); v.push(1); ... v }`
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## Common Patterns
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- Builder pattern: `MyStruct::new().with_field(val).build()`
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- Newtype pattern: `struct UserId(u64);` for type safety without runtime cost.
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- Type state pattern: use generics to encode state in the type system.
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- Interior mutability: `Cell<T>`, `RefCell<T>` for single-threaded, `Mutex<T>` for multi-threaded.
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