Crate bigdecimal

A Big Decimal

BigDecimal allows storing any real number to arbitrary precision; which avoids common floating point errors (such as 0.1 + 0.2 ≠ 0.3) at the cost of complexity.

Internally, BigDecimal uses a BigInt object, paired with a 64-bit integer which determines the position of the decimal point. Therefore, the precision is not actually arbitrary, but limited to 2⁶³ decimal places.

Common numerical operations are overloaded, so we can treat them the same way we treat other numbers.

It is not recommended to convert a floating point number to a decimal directly, as the floating point representation may be unexpected.

Example

use bigdecimal::BigDecimal;
use std::str::FromStr;

let input = "0.8";
let dec = BigDecimal::from_str(&input).unwrap();
let float = f32::from_str(&input).unwrap();

println!("Input ({}) with 10 decimals: {} vs {})", input, dec, float);

Re-exports

• pub extern crate num_bigint;
• pub extern crate num_traits;
• pub use rounding::RoundingMode;

Modules

• rounding
  Rounding structures and subroutines

Structs

• BigDecimal
  A big decimal type.

Enums

• ParseBigDecimalError

Traits

• FromPrimitive
  A generic trait for converting a number to a value.
• Num
  The base trait for numeric types, covering 0 and 1 values, comparisons, basic numeric operations, and string conversion.
• One
  Defines a multiplicative identity element for Self.
• Signed
  Useful functions for signed numbers (i.e. numbers that can be negative).
• ToPrimitive
  A generic trait for converting a value to a number.
• Zero
  Defines an additive identity element for Self.