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+# Rust Book Notes
+
+## Basics (Chapter 3)
+
+### Variables and Mutability
+
+- Variables are immutable by default
+- `mut` keyword makes variables mutable
+- Constants
+  - are always immutable
+  - must be set to constant expressions
+  - must be type annotated
+- Variables can always be shadowed (i.e. reassigned with `let`)
+- Variable types cannot be mutated
+
+### Data Types
+
+- Types must be annotated when they cannot be infered
+- Integers can be signed or unsigned and have an explicit size
+- Floats have single or double precision
+- Bools are bools
+- Character types represent a Unicode scalar value
+- Tuples bind different typed values together
+- Tuple values are accesed with period e.g. `x.0`
+- Arrays
+  - have fixed lengths
+  - all elements have same type
+  - data is allocated on stack rather than heap
+  - elements accessed via `a[0]`
+  - out-of-bounds array access is a runtime panic
+
+### Functions
+
+- Function names are `snake_case`
+- Function declaration order is irrelevant
+- Function params must be type annotated
+- Function bodies are statements with an optional ending expression
+- Expressions do not end with semicolons
+- The final function expression is the return value
+- The `return` keyword can be explicit mid-function
+
+### Comments
+
+- Start with `// two slashes`
+- Usually appear on separate lines above annotated code
+- But can also appear `// on same line`
+
+### Control Flow
+
+- `if` conditions do not appear in parenthesis
+- Multiple conditions are handled with `else if`
+- `if`s are expressions and thus can be assigned to variables
+- `loop` block will loop until `break`
+- Or just use `while`
+- `for` loops are the best choice as usual
+
+## Ownership (Chapter 4)
+
+### Ownership
+
+- Each Rust value has an *owner*
+- There can only be one owner at a time
+- When an owner goes out of scope, the value is dropped
+- Scopes are similar to other languages behavior
+- `String`s are allocated on the heap
+- When variables go out of scope Rust calls a `drop` function
+- Shallow heap variables copies are actually *moves*
+- Stack values are `Copy`ied (trait) as expected
+- Semantics for passing values to functions are same
+- References allow refering to values with taking ownership
+- `&s1` is a reference to `s1`
+- References cannot be mutated
+- Mutable references (`&mut s1`) can be mutated
+- Only one mutable reference to a given value can exist in scope
+- At any given time you can have *either* one mutable references, or many immutable references
+- References must always be valid
+
+### Slices
+
+