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)

Constructor Detail

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

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

def self.new(num : Float) #

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) #

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) #

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

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

Creates a new BigDecimal from Int.

def self.new(str : String) #

Creates a new BigDecimal from a String.

Allows only valid number strings with an optional negative sign.

Instance Method Detail

def *(other : BigDecimal) : BigDecimal #

def *(other : Number) : BigDecimal #

def **(other : Int) : BigDecimal #

Raises the decimal to the otherth power

require "big"

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

def +(other : BigDecimal) : BigDecimal #

def +(other : Number) : BigDecimal #

def -(other : BigDecimal) : BigDecimal #

def -(other : Number) : BigDecimal #

def - : BigDecimal #

def /(other : BigDecimal) : BigDecimal #

def /(other : BigInt) : BigDecimal #

def /(other : BigFloat) : BigDecimal #

def /(other : BigRational) : BigRational #

def /(other : Int8) : BigDecimal #

def /(other : UInt8) : BigDecimal #

def /(other : Int16) : BigDecimal #

def /(other : UInt16) : BigDecimal #

def /(other : Int32) : BigDecimal #

def /(other : UInt32) : BigDecimal #

def /(other : Int64) : BigDecimal #

def /(other : UInt64) : BigDecimal #

def /(other : Int128) : BigDecimal #

def /(other : UInt128) : BigDecimal #

def /(other : Float32) : BigDecimal #

def /(other : Float64) : BigDecimal #

def <=>(other : BigDecimal) : Int32 #
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 greater 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 : Int | Float | BigRational) #

def ==(other : BigDecimal) : Bool #
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 ceil : BigDecimal #

Rounds towards positive infinity.

def clone #

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

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 floor : BigDecimal #

Rounds towards negative infinity.

def hash(hasher) #
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) : BigInt #

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

def round(digits : Number, base = 10, *, mode : RoundingMode = :ties_even) : BigDecimal #
Description copied from struct Number

Rounds this number to a given precision.

Rounds to the specified number of digits after the decimal place, (or before if negative), in base base.

The rounding mode controls the direction of the rounding. The default is RoundingMode::TIES_EVEN which rounds to the nearest integer, with ties (fractional value of 0.5) being rounded to the even neighbor (Banker's rounding).

-1763.116.round(2) # => -1763.12

def round_away : BigDecimal #

Rounds towards the nearest integer. If both neighboring integers are equidistant, rounds away from zero.

def round_even : BigDecimal #

Rounds towards the nearest integer. If both neighboring integers are equidistant, rounds towards the even neighbor (Banker's rounding).

def scale : UInt64 #

def scale_to(new_scale : BigDecimal) : BigDecimal #

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

def to_big_d #

def to_big_f #

Converts to BigFloat.

def to_big_i : BigInt #

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

def to_big_r : BigRational #

def to_f : Float64 #

Converts to Float64. Raises OverflowError in case of overflow.

def to_f! : Float64 #

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

def to_f32 : Float32 #

Converts to Float32. Raises OverflowError in case of overflow.

def to_f32! #

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

def to_f64 : Float64 #

Converts to Float64. Raises OverflowError in case of overflow.

def to_f64! : Float64 #

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

def to_i : Int32 #

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

def to_i! : Int32 #

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

def to_i16 : Int16 #

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

def to_i16! #

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

def to_i32 : Int32 #

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

def to_i32! : Int32 #

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

def to_i64 : Int64 #

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

def to_i64! #

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

def to_i8 : Int8 #

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

def to_i8! #

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) : Nil #
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_u : UInt32 #

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

def to_u! : UInt32 #

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_u16 : UInt16 #

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

def to_u16! #

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_u32 : UInt32 #

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

def to_u32! : UInt32 #

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_u64 : UInt64 #

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

def to_u64! #

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_u8 : UInt8 #

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

def to_u8! #

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.

def trunc : BigDecimal #

Rounds towards zero.

def value : BigInt #

def zero? : Bool #
Description copied from struct Number

Returns true if self is equal to zero.

0.zero? # => true
5.zero? # => false