/Crystal

# struct BigDecimal

## Overview

A `BigDecimal` can represent arbitrarily large precision decimals.

It is internally represented by a pair of `BigInt` and `UInt64`: value and scale. Value contains the actual value, and scale tells the decimal point place. E.g. when value is `1234` and scale `2`, the result is `12.34`.

The general idea and some of the arithmetic algorithms were adapted from the MIT/APACHE-licensed bigdecimal-rs.

## Defined in:

big.cr
big/big_decimal.cr
big/number.cr

## Constant Summary

DEFAULT_MAX_DIV_ITERATIONS = `100_u64`
TEN = `BigInt.new(10)`
ZERO = `BigInt.new(0)`

## Instance Method Summary

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## Constructor Detail

### def self.new(value : BigInt, scale : UInt64)Source

Creates a new `BigDecimal` from `BigInt` value and `UInt64` scale, which matches the internal representation.

### def self.new(num : Float)Source

Creates a new `BigDecimal` from `Float`.

NOTE Floats are fundamentally less precise than BigDecimals, which makes initialization from them risky.

### def self.new(num : BigRational)Source

Creates a new `BigDecimal` from `BigRational`.

NOTE BigRational are fundamentally more precise than BigDecimals, which makes initialization from them risky.

### def self.new(num : BigDecimal)Source

Returns num. Useful for generic code that does `T.new(...)` with `T` being a `Number`.

### def self.new(num : Int = 0, scale : Int = 0)Source

Creates a new `BigDecimal` from `Int`.

### def self.new(str : String)Source

Creates a new `BigDecimal` from a `String`.

Allows only valid number strings with an optional negative sign.

## Instance Method Detail

### def **(other : Int) : BigDecimalSource

Raises the decimal to the otherth power

```require "big"

BigDecimal.new(1234, 2) ** 2 # => 152.2756```

### def <=>(other : BigDecimal) : Int32Source

Description copied from module Comparable(BigDecimal)

The comparison operator. Returns `0` if the two objects are equal, a negative number if this object is considered less than other, a positive number if this object is considered greter than other, or `nil` if the two objects are not comparable.

Subclasses define this method to provide class-specific ordering.

The comparison operator is usually used to sort values:

```# Sort in a descending way:
[3, 1, 2].sort { |x, y| y <=> x } # => [3, 2, 1]

# Sort in an ascending way:
[3, 1, 2].sort { |x, y| x <=> y } # => [1, 2, 3]```

### def ==(other : BigDecimal) : BoolSource

Description copied from module Comparable(BigDecimal)

Compares this object to other based on the receiver’s `#<=>` method, returning `true` if it returns `0`.

Also returns `true` if this and other are the same object.

### def div(other : BigDecimal, max_div_iterations = DEFAULT_MAX_DIV_ITERATIONS) : BigDecimalSource

Divides `self` with another `BigDecimal`, with a optionally configurable max_div_iterations, which defines a maximum number of iterations in case the division is not exact.

```BigDecimal.new(1).div(BigDecimal.new(2))    # => BigDecimal(@value=5, @scale=2)
BigDecimal.new(1).div(BigDecimal.new(3), 5) # => BigDecimal(@value=33333, @scale=5)```

### def hash(hasher)Source

Description copied from class Object

Appends this object's value to hasher, and returns the modified hasher.

Usually the macro `def_hash` can be used to generate this method. Otherwise, invoke `#hash(hasher)` on each object's instance variables to accumulate the result:

```def hash(hasher)
hasher = @some_ivar.hash(hasher)
hasher = @some_other_ivar.hash(hasher)
hasher
end```

### def normalize_quotient(other : BigDecimal, quotient : BigInt) : BigIntSource

Returns the quotient as absolutely negative if `self` and other have different signs, otherwise returns the quotient.

### def scale_to(new_scale : BigDecimal) : BigDecimalSource

Scales a `BigDecimal` to another `BigDecimal`, so they can be computed easier.

### def to_big_fSource

Converts to `BigFloat`.

### def to_big_iSource

Converts to `BigInt`. Truncates anything on the right side of the decimal point.

### def to_fSource

Converts to `Float64`. Raises `OverflowError` in case of overflow.

### def to_f!Source

Converts to `Float64`. In case of overflow a wrapping is performed.

### def to_f32Source

Converts to `Float32`. Raises `OverflowError` in case of overflow.

### def to_f32!Source

Converts to `Float32`. In case of overflow a wrapping is performed.

### def to_f64Source

Converts to `Float64`. Raises `OverflowError` in case of overflow.

### def to_f64!Source

Converts to `Float64`. In case of overflow a wrapping is performed.

### def to_iSource

Converts to `Int32`. Truncates anything on the right side of the decimal point. Raises `OverflowError` in case of overflow.

### def to_i!Source

Converts to `Int32`. Truncates anything on the right side of the decimal point. In case of overflow a wrapping is performed.

### def to_i16Source

Converts to `Int16`. Truncates anything on the right side of the decimal point. Raises `OverflowError` in case of overflow.

### def to_i16!Source

Converts to `Int16`. Truncates anything on the right side of the decimal point. In case of overflow a wrapping is performed.

### def to_i32Source

Converts to `Int32`. Truncates anything on the right side of the decimal point. Raises `OverflowError` in case of overflow.

### def to_i32!Source

Converts to `Int32`. Truncates anything on the right side of the decimal point. In case of overflow a wrapping is performed.

### def to_i64Source

Converts to `Int64`. Truncates anything on the right side of the decimal point. Raises `OverflowError` in case of overflow.

### def to_i64!Source

Converts to `Int64`. Truncates anything on the right side of the decimal point. In case of overflow a wrapping is performed.

### def to_i8Source

Converts to `Int8`. Truncates anything on the right side of the decimal point. Raises `OverflowError` in case of overflow.

### def to_i8!Source

Converts to `Int8`. Truncates anything on the right side of the decimal point. In case of overflow a wrapping is performed.

### def to_s(io : IO) : NilSource

Description copied from class Object

Appends a `String` representation of this object to the given `IO` object.

An object must never append itself to the io argument, as this will in turn call `#to_s(io)` on it.

### def to_uSource

Converts to `UInt32`. Truncates anything on the right side of the decimal point. Raises `OverflowError` in case of overflow.

### def to_u!Source

Converts to `UInt32`. Truncates anything on the right side of the decimal point, converting negative to positive. In case of overflow a wrapping is performed.

### def to_u16Source

Converts to `UInt16`. Truncates anything on the right side of the decimal point. Raises `OverflowError` in case of overflow.

### def to_u16!Source

Converts to `UInt16`. Truncates anything on the right side of the decimal point, converting negative to positive. In case of overflow a wrapping is performed.

### def to_u32Source

Converts to `UInt32`. Truncates anything on the right side of the decimal point. Raises `OverflowError` in case of overflow.

### def to_u32!Source

Converts to `UInt32`. Truncates anything on the right side of the decimal point, converting negative to positive. In case of overflow a wrapping is performed.

### def to_u64Source

Converts to `UInt64`. Truncates anything on the right side of the decimal point. Raises `OverflowError` in case of overflow.

### def to_u64!Source

Converts to `UInt64`. Truncates anything on the right side of the decimal point, converting negative to positive. In case of overflow a wrapping is performed.

### def to_u8Source

Converts to `UInt8`. Truncates anything on the right side of the decimal point. Raises `OverflowError` in case of overflow.

### def to_u8!Source

Converts to `UInt8`. Truncates anything on the right side of the decimal point, converting negative to positive. In case of overflow a wrapping is performed.