Rust: personal reference
Methods on built-ins Hashmap .entry — Used for in-place manipulation of the value for a corresponding key, scores.entry(team_id) .or_default — Insert an empty default value if the key is not present, returning a mutable reference, scores.entry(team_id).or_default() .or_insert — Insert a populated default value if the key is not present, also returning a mutable reference, sat_scores.entry(student_id).or_insert(400) String slice .len — Get the length of the string slice, name.len() .is_empty — Check if the string slice is empty, name.is_empty() .to_string — Convert a string slice to a String, name.to_string(); compare, contrast with String::from Keywords Variable Bindings and Data Declaration let — Declare a variable const — Declare a compile-time constant static — Declare a static variable (global variable with a fixed memory location) mut — Mark a binding as mutable ref — Bind by reference Type System type — Create a type alias struct — Define a structure/record type enum — Define an enumeration type trait — Define an interface type impl — Implement methods or traits dyn — Dynamic dispatch to a trait object Self — Type alias for the implementing type within a trait or impl self — Method receiver or current module super — Parent module where — Add constraints to generic types Control Flow if — Conditional branching else — Alternative branch in conditional match — Pattern matching loop — Infinite loop while — Conditional loop for — Iterator-based loop in — Part of for loop syntax and pattern matching break — Exit a loop early continue — Skip to the next loop iteration return — Return from a function Functions and Closures fn — Define a function move — Force closure to take ownership of captured variables async — Define an asynchronous function or block await — Suspend execution until an async result is ready Memory Management unsafe — Denote unsafe code block extern — Link to external functions or crates raw — Raw pointer operations (used with references) Modules and Visibility mod — Define a module pub — Make an item public use — Import items from other modules crate — Reference the current crate or external crate as — Rename or alias in imports Macros macro_rules! — Define a declarative macro Type Operations as — Type casting _ — Wildcard pattern or type placeholder Reserved for Future Use (No Functionality Yet) abstract become box do final macro override priv try typeof unsized virtual yield