Rust Variables

	Types	Literals
Signed integers	i8, i16, i32, i64, i128, isize	-10, 0, 1_000, 123_i64
Unsigned integers	u8, u16, u32, u64, u128, usize	0, 123, 10_u16
Floating point numbers	f32, f64	3.14, -10.0e20, 2_f32
Unicode scalar values	char	'a', 'α', '∞'
Booleans	bool	true, false

• iN, uN, and fN are N bits wide,
• isize and usize are the width of a pointer,
• char is 32 bits wide,
• bool is 8 bits wide.

Bit Widths

Signed Integer Types (iN)

• Signed integers use one bit to represent the sign (positive or negative), and the remaining bits for the value (magnitude). They can represent both negative and positive numbers.

Type	Bit Width	Range
i8	8 bits	-128 to 127
i16	16 bits	-32,768 to 32,767
i32	32 bits	-2,147,483,648 to 2,147,483,647
i64	64 bits	-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
i128	128 bits	Extremely large range
isize	Depends on the platform (32 bits on 32-bit systems, 64 bits on 64-bit systems)

Unsigned Integer Types (uN)

• Unsigned integers only represent non-negative numbers, and since there’s no need for a sign bit, all bits are used for the magnitude.

Type	Bit Width	Range
u8	8 bits	0 to 255
u16	16 bits	0 to 65,535
u32	32 bits	0 to 4,294,967,295
u64	64 bits	0 to 18,446,744,073,709,551,615
u128	128 bits	Extremely large range
usize	Depends on the platform (32 bits on 32-bit systems, 64 bits on 64-bit systems)

Rust’s Approach to Integer Overflow

Rust has several methods to handle integer overflow:

1. Checked Arithmetic (default in debug mode): When an overflow is detected, it panics (as seen here).

2. Wrapping Arithmetic: The result wraps around, mimicking how arithmetic works in C. For example, i16::MAX + 1 will wrap around to i16::MIN.

   rust

   Copy code

   (a * b).wrapping_add(b * c).wrapping_add(c * a);

3. Saturating Arithmetic: The result is clamped to the maximum or minimum value if it overflows.

   rust

   Copy code

   (a * b).saturating_add(b * c).saturating_add(c * a);

4. Overflowing Arithmetic: Returns a tuple with the result and a Boolean indicating whether an overflow occurred.

   rust

   Copy code

   let (result, overflowed) = (a * b).overflowing_add(b * c).overflowing_add(c * a);

5. Carrying Arithmetic: Similar to overflowing, but it’s useful for multi-word arithmetic (for handling large numbers across multiple registers).