More in Go & Rust — page 13
Stack vs. Heap: Where Go Puts Your Data
The stack is a fast, last-in-first-out region for local, fixed-size data. The heap is slower, flexible memory for dynamic data or values that escape a function's scope.
Rust Cargo Workspaces: A Monorepo Control Panel
A Cargo Workspace is a control panel for a multi-crate Rust project, unifying dependencies and build artifacts. Use it for related binaries and libraries to ensure consistent builds.
Go's `internal` Directory: Private by Convention
Go's `internal` directory creates private packages within your module, making them inaccessible to external projects. Use it for helper logic you don't want to support as a public API.
Rust's Module-to-Filesystem Mapping
Rust's module system maps directly to your file system. A `mod foo;` statement tells the compiler to look for `foo.rs` or `foo/mod.rs`. This is how you organize any multi-file Rust project.
Cargo.toml: Rust's Project Recipe
Cargo.toml is your Rust project's recipe, telling the compiler what to build and what dependencies it needs. It defines metadata, production dependencies, and dev-only dependencies for testing.
Rust Methods: Attaching Behavior to Data
Rust methods are functions attached to your data structures, defined in an `impl` block. Instead of `do_thing(my_struct)`, you call `my_struct.do_thing()`. The key footgun: `instance.name()` calls a method, but `instance.name` accesses a field.
Rust Item Visibility: Private by Default
In Rust, all items are private by default. Think of modules as locked rooms; you need the `pub` keyword to unlock the door. This is crucial for creating a public API or letting modules interact.
Go's Entry Point: The `main` Package and Function
A Go program's entry point is `package main`. The compiler finds this package and its `main()` function to create a runnable binary. The footgun is naming a library `main`; this name is reserved for executables and will cause build confusion.
Rust Modules: Your Code's File System
Think of Rust modules as a file system for your code, grouping logic and hiding details. You declare them with `mod`, and Rust finds the code in corresponding files. The footgun: items are private by default, so you must use `pub` to expose them.
Rust Crates: Your Unit of Compilation
A crate is the smallest unit of code the Rust compiler handles—either a runnable program (binary) or a shareable library. A package, defined by Cargo.toml, bundles one or more crates. The footgun: a package can have many binaries but only one library.
Rust's Arc<T>: Share Data Ownership Across Threads
Rust's `Arc<T>` lets multiple threads share ownership of heap data. It's a smart pointer that counts references atomically. Use it for shared caches or config. The footgun: `Arc` only makes sharing safe, not mutation—you still need a `Mutex` for that.
Rust's Rc<T>: Shared Ownership on a Single Thread
Rust's `Rc<T>` enables shared ownership within a single thread. Think of it as a counter on a heap-allocated resource: cloning an `Rc` increments the count, and the resource is freed only when the count hits zero. Use it for graph nodes with multiple owners.
Go's sync.Map: A Specialized Concurrent Map
Go's `sync.Map` is a concurrent map optimized for keys written once and read many times. It's ideal for long-lived caches, but it's not a generic replacement for a map with a mutex. The footgun is using it for frequent writes, which can be slower.
Rust Enums: Attaching Data Directly to Variants
A Rust enum variant can carry its own data, acting like a mini-struct. This is perfect for modeling states with different payloads, like a `Result` that holds either a value or an error. The footgun is using a separate struct to pair an enum with.
Rust's Two String Types: String vs. &str
Think of `String` as an owned, growable text buffer on the heap, while `&str` is a borrowed, fixed-size view into string data. This distinction is key to Rust's memory safety. Functions often take `&str` to flexibly accept both types.
Rust Slices (&[T]): Views Without Ownership
A Rust slice is a borrowed view into a contiguous sequence of data, like an array or Vec, without taking ownership. Use it to write functions that operate on parts of a collection efficiently. The footgun: a slice cannot outlive the data it points to.
Rust HashMap: Fast, Secure Key-Value Storage
A Rust `HashMap` is like a dictionary, mapping unique keys to values for fast lookups. Use it for caching or frequency counting. The footgun: never modify a key after insertion, as changing its hash will break the map's internal logic.
Rust Vectors: Your Go-To Growable List
A `Vec<T>` is Rust's smart, growable array. It automatically gets more memory when full, keeping items together for fast access. Use it for lists of unknown size. The footgun: frequent reallocations can be slow if you don't pre-allocate capacity.
Go Maps: Your Built-in Hash Table
Go maps are the language's built-in hash tables for fast key-value lookups. Use `make(map[K]V)` to initialize one before writing. The biggest footgun is writing to a `nil` map, which causes a runtime panic. Always initialize your maps first.
Using Box<T> for Heap Allocation in Rust
Rust's `Box<T>` is a smart pointer that moves data from the stack to the heap. It's essential for creating recursive types, like linked lists, whose size would otherwise be infinite. The main footgun is in FFI: never wrap a C-allocated pointer in a `Box`.