Money v2.0.1 Money View Source

Money implements a set of functions to store, retrieve, convert and perform arithmetic on a Money.t type that is composed of a currency code and a decimal currency amount.

Money is very opinionated in the interests of serving as a dependable library that can underpin accounting and financial applications.

This opinion expressed by ensuring that:

Money must always have both a amount and a currency code.
The currency code must always be valid.
Money arithmetic can only be performed when both operands are of the same currency.
Money amounts are represented as a Decimal.
Money is serialised to the database as a custom Postgres composite type that includes both the amount and the currency. Therefore for Ecto serialization Postgres is assumed as the data store. Serialization is entirely optional and Ecto is not a package dependency.
All arithmetic functions work in fixed point decimal. No rounding occurs automatically (unless expressly called out for a function).
Explicit rounding obeys the rounding rules for a given currency. The rounding rules are defined by the Unicode consortium in its CLDR repository as implemented by the hex package ex_cldr. These rules define the number of fractional digits for a currency and the rounding increment where appropriate.

Link to this section Summary

Types

currency_code()

t()

Money is composed of an atom representation of an ISO4217 currency code and a Decimal representation of an amount

Functions

add(money1, money2)

Add two Money values

add!(money_1, money_2)

Add two Money values and raise on error

cmp(money1, money2)

Compares two Money values numerically. If the first number is greater than the second :gt is returned, if less than :lt is returned, if both numbers are equal :eq is returned

cmp!(money_1, money_2)

Compares two Money values numerically and raises on error

compare(money1, money2)

Compares two Money values numerically. If the first number is greater than the second #Integer<1> is returned, if less than Integer<-1> is returned. Otherwise, if both numbers are equal Integer<0> is returned

compare!(money_1, money_2)

Compares two Money values numerically and raises on error

div(money, number)

Divide a Money value by a number

div!(money, number)

Divide a Money value by a number and raise on error

equal?(arg1, arg2)

Returns a boolean indicating if two Money values are equal

from_float(currency_code, amount)

Returns a %Money{} struct from a currency code and a float amount, or an error tuple of the form {:error, {exception, message}}

from_float!(currency_code, amount)

from_integer(amount, currency)

Convert an integer representation of money into a Money struct

from_tuple(arg)

Returns a %Money{} struct from a tuple consistenting of a currency code and a currency amount. The format of the argument is a 2-tuple where

from_tuple!(arg)

Returns a %Money{} struct from a tuple consistenting of a currency code and a currency amount. Raises an exception if the currency code is invalid

get_env(key, default, atom)

mult(money, number)

Multiply a Money value by a number

mult!(money, number)

Multiply a Money value by a number and raise on error

new(currency_code, amount)

Returns a %Money{} struct from a currency code and a currency amount or an error tuple of the form {:error, {exception, message}}

new!(currency_code, amount)

Returns a %Money{} struct from a currency code and a currency amount. Raises an exception if the current code is invalid

reduce(money)

Calls Decimal.reduce/1 on the given %Money{}

round(money, opts \\ [])

Round a Money value into the acceptable range for the defined currency

split(money, parts)

Split a Money value into a number of parts maintaining the currency’s precision and rounding and ensuring that the parts sum to the original amount

sub(money1, money2)

Subtract one Money value struct from another

sub!(a, b)

Subtract one Money value struct from another and raise on error

to_currency(money, to_currency, rates \\ Money.ExchangeRates.latest_rates())

Convert money from one currency to another

to_currency!(money, currency)

Convert money from one currency to another and raises on error

to_currency!(money, currency, rates)

to_decimal(money)

Returns the amount part of a Money type as a Decimal

to_integer_exp(money)

Returns a tuple comprising the currency code, integer amount, exponent and remainder

to_string(money, options \\ [])

Returns a formatted string representation of a Money{}

to_string!(money, options \\ [])

Returns a formatted string representation of a Money{} or raises if there is an error

validate_currency(currency_code)

Link to this section Types

currency_code()

currency_code() :: atom()

t()

t() :: %Money{amount: Decimal.t(), currency: atom()}

Money is composed of an atom representation of an ISO4217 currency code and a Decimal representation of an amount.

Link to this section Functions

add(money1, money2)

add(money_1 :: Money.t(), money_2 :: Money.t()) :: Money.t()

Add two Money values.

Options

money_1 and money_2 are any valid Money.t types returned by Money.new/2

Returns

{:ok, money} or
{:error, reason}

Example

iex> Money.add Money.new(:USD, 200), Money.new(:USD, 100)
{:ok, Money.new(:USD, 300)}

iex> Money.add Money.new(:USD, 200), Money.new(:AUD, 100)
{:error, {ArgumentError, "Cannot add monies with different currencies. " <>
  "Received :USD and :AUD."}}

add!(money_1, money_2)

Add two Money values and raise on error.

Options

money_1 and money_2 are any valid Money.t types returned by Money.new/2

Returns

{:ok, money} or
raises an exception

Examples

iex> Money.add! Money.new(:USD, 200), Money.new(:USD, 100)
#Money<:USD, 300>

Money.add! Money.new(:USD, 200), Money.new(:CAD, 500)
** (ArgumentError) Cannot add two %Money{} with different currencies. Received :USD and :CAD.

cmp(money1, money2)

cmp(money_1 :: Money.t(), money_2 :: Money.t()) ::
  :gt |
  :eq |
  :lt |
  {:error, {Exception.t(), String.t()}}

Compares two Money values numerically. If the first number is greater than the second :gt is returned, if less than :lt is returned, if both numbers are equal :eq is returned.

Options

money_1 and money_2 are any valid Money.t types returned by Money.new/2

Returns

:gt | :eq | :lt or
{:error, {Exception.t, String.t}}

Examples

iex> Money.cmp Money.new(:USD, 200), Money.new(:USD, 100)
:gt

iex> Money.cmp Money.new(:USD, 200), Money.new(:USD, 200)
:eq

iex> Money.cmp Money.new(:USD, 200), Money.new(:USD, 500)
:lt

iex> Money.cmp Money.new(:USD, 200), Money.new(:CAD, 500)
{:error,
 {ArgumentError,
  "Cannot compare monies with different currencies. Received :USD and :CAD."}}

cmp!(money_1, money_2)

Compares two Money values numerically and raises on error.

Options

money_1 and money_2 are any valid Money.t types returned by Money.new/2

Returns

:gt | :eq | :lt or
raises an exception

Examples

Money.cmp! Money.new(:USD, 200), Money.new(:CAD, 500)
** (ArgumentError) Cannot compare monies with different currencies. Received :USD and :CAD.

compare(money1, money2)

compare(money_1 :: Money.t(), money_2 :: Money.t()) ::
  -1 |
  0 |
  1 |
  {:error, {Exception.t(), String.t()}}

Options

money_1 and money_2 are any valid Money.t types returned by Money.new/2

Returns

-1 | 0 | 1 or
{:error, {Exception.t, String.t}}

Examples

iex> Money.compare Money.new(:USD, 200), Money.new(:USD, 100)
1

iex> Money.compare Money.new(:USD, 200), Money.new(:USD, 200)
0

iex> Money.compare Money.new(:USD, 200), Money.new(:USD, 500)
-1

iex> Money.compare Money.new(:USD, 200), Money.new(:CAD, 500)
{:error,
 {ArgumentError,
  "Cannot compare monies with different currencies. Received :USD and :CAD."}}

compare!(money_1, money_2)

Compares two Money values numerically and raises on error.

Options

money_1 and money_2 are any valid Money.t types returned by Money.new/2

Returns

-1 | 0 | 1 or
raises an exception

Examples

Money.compare! Money.new(:USD, 200), Money.new(:CAD, 500)
** (ArgumentError) Cannot compare monies with different currencies. Received :USD and :CAD.

div(money, number)

div(Money.t(), Cldr.Math.number_or_decimal()) :: Money.t()

Divide a Money value by a number.

Options

money is any valid Money.t types returned by Money.new/2
number is an integer, float or Decimal.t

Note that dividing one %Money{} by another is not supported.

Returns

{:ok, money} or
{:error, reason}

Example

iex> Money.div Money.new(:USD, 200), 2
{:ok, Money.new(:USD, 100)}

iex> Money.div(Money.new(:USD, 200), "xx")
{:error, {ArgumentError, "Cannot divide money by \"xx\""}}

div!(money, number)

Divide a Money value by a number and raise on error.

Options

money is any valid Money.t types returned by Money.new/2
number is an integer, float or Decimal.t

Returns

a Money.t struct or
raises an exception

Examples

iex> Money.div Money.new(:USD, 200), 2
{:ok, Money.new(:USD, 100)}

Money.div(Money.new(:USD, 200), "xx")
** (ArgumentError) "Cannot divide money by \"xx\""]}}

equal?(arg1, arg2)

equal?(money_1 :: Money.t(), money_2 :: Money.t()) :: boolean()

Returns a boolean indicating if two Money values are equal

Options

money_1 and money_2 are any valid Money.t types returned by Money.new/2

Returns

true or false

Example

iex> Money.equal? Money.new(:USD, 200), Money.new(:USD, 200)
true

iex> Money.equal? Money.new(:USD, 200), Money.new(:USD, 100)
false

from_float(currency_code, amount)

Returns a %Money{} struct from a currency code and a float amount, or an error tuple of the form {:error, {exception, message}}.

Floats are fraught with danger in computer arithmetic due to the unexpected loss of precision during rounding. The IEEE754 standard indicates that a number with a precision of 16 should round-trip convert without fidelity. This function supports numbers with a precision up to 15 digits and will error if the provided amount is outside that range.

Note that Money cannot detect lack of precision or rounding errors introduced upstream. This function therefore should be used with great care and its use should be considered potentially harmful.

Options

currency_code is an ISO4217 three-character upcased binary or atom
amount is a float

Examples

iex> Money.from_float 1.23456, :USD
#Money<:USD, 1.23456>

iex> Money.from_float 1.234567890987656, :USD
{:error,
  {Money.InvalidAmountError,
    "The precision of the float 1.234567890987656 is " <>
    "greater than 15 which could lead to unexpected results. " <>
    "Reduce the precision or call Money.new/2 with a Decimal or String amount"}}

from_float!(currency_code, amount)

from_integer(amount, currency)

Convert an integer representation of money into a Money struct.

This is the inverse operation of Money.to_integer_exp/1.

Options

integer is an integer representation of a mooney item including any decimal digits. ie. 20000 would interpreted to mean $200.00
currency is the currency code for the integer. The assumed decimal places is derived from the currency code.

Returns

A Money struct or
{:error, {Cldr.UnknownCurrencyError, message}}

Examples

iex> Money.from_integer(20000, :USD)
#Money<:USD, 200.00>

iex> Money.from_integer(200, :JPY)
#Money<:JPY, 200>

iex> Money.from_integer(20012, :USD)
#Money<:USD, 200.12>

from_tuple(arg)

from_tuple({binary(), number()}) :: Money.t()

Returns a %Money{} struct from a tuple consistenting of a currency code and a currency amount. The format of the argument is a 2-tuple where:

Options

currency_code is an ISO4217 three-character upcased binary
amount is an integer or Decimal

This function is typically called from Ecto when it’s loading a %Money{} struct from the database.

Example

iex> Money.from_tuple({"USD", 100})
#Money<:USD, 100>

iex> Money.from_tuple({100, "USD"})
#Money<:USD, 100>

from_tuple!(arg)

Returns a %Money{} struct from a tuple consistenting of a currency code and a currency amount. Raises an exception if the currency code is invalid.

Options

currency_code is an ISO4217 three-character upcased binary
amount is an integer, float or Decimal

This function is typically called from Ecto when it’s loading a %Money{} struct from the database.

Example

iex> Money.from_tuple!({"USD", 100})
#Money<:USD, 100>

Money.from_tuple!({"NO!", 100})
** (Money.UnknownCurrencyError) Currency "NO!" is not known
    (ex_money) lib/money.ex:130: Money.new!/1

get_env(key, default, atom)

mult(money, number)

mult(Money.t(), Cldr.Math.number_or_decimal()) :: Money.t()

Multiply a Money value by a number.

Options

money is any valid Money.t type returned by Money.new/2
number is an integer, float or Decimal.t

Note that multipling one %Money{} by another is not supported.

Returns

{:ok, money} or
{:error, reason}

Example

iex> Money.mult(Money.new(:USD, 200), 2)
{:ok, Money.new(:USD, 400)}

iex> Money.mult(Money.new(:USD, 200), "xx")
{:error, {ArgumentError, "Cannot multiply money by \"xx\""}}

mult!(money, number)

mult!(Money.t(), Cldr.Math.number_or_decimal()) :: Money.t() | none()

Multiply a Money value by a number and raise on error.

Options

money is any valid Money.t types returned by Money.new/2
number is an integer, float or Decimal.t

Returns

a Money.t or
raises an exception

Examples

iex> Money.mult!(Money.new(:USD, 200), 2)
#Money<:USD, 400>

Money.mult!(Money.new(:USD, 200), :invalid)
** (ArgumentError) Cannot multiply money by :invalid

new(currency_code, amount)

new(number(), binary()) :: Money.t()

Returns a %Money{} struct from a currency code and a currency amount or an error tuple of the form {:error, {exception, message}}.

Options

currency_code is an ISO4217 three-character upcased binary or atom
amount is an integer, string or Decimal

Note that the currency_code and amount arguments can be supplied in either order,

Examples

iex> Money.new(:USD, 100)
#Money<:USD, 100>

iex> Money.new(100, :USD)
#Money<:USD, 100>

iex> Money.new("USD", 100)
#Money<:USD, 100>

iex> Money.new("thb", 500)
#Money<:THB, 500>

iex> Money.new("EUR", Decimal.new(100))
#Money<:EUR, 100>

iex> Money.new(:EUR, "100.30")
#Money<:EUR, 100.30>

iex> Money.new(:XYZZ, 100)
{:error, {Money.UnknownCurrencyError, "The currency :XYZZ is invalid"}}

iex(1)> Money.new 123.445, :USD
{:error,
 {Money.InvalidAmountError,
  "Float amounts are not supported in new/2 due to potenial " <>
  "rounding and precision issues.  If absolutely required, " <>
  "use Money.from_float/2"}}

new!(currency_code, amount)

Returns a %Money{} struct from a currency code and a currency amount. Raises an exception if the current code is invalid.

Options

currency_code is an ISO4217 three-character upcased binary or atom
amount is an integer, float or Decimal

Examples

Money.new!(:XYZZ, 100)
** (Money.UnknownCurrencyError) Currency :XYZZ is not known
  (ex_money) lib/money.ex:177: Money.new!/2

reduce(money)

reduce(Money.t()) :: Money.t()

Calls Decimal.reduce/1 on the given %Money{}

This will reduce the coefficient and exponent of the decimal amount in a standard way that may aid in native comparison of %Money{} items.

Example

iex> x = %Money{currency: :USD, amount: %Decimal{sign: 1, coef: 42, exp: 0}}
#Money<:USD, 42>
iex> y = %Money{currency: :USD, amount: %Decimal{sign: 1, coef: 4200000000, exp: -8}}
#Money<:USD, 42.00000000>
iex> x == y
false
iex> y = Money.reduce(x)
#Money<:USD, 42>
iex> x == y
true

round(money, opts \\ [])

round(Money.t(), Keyword.t()) :: Money.t()

Round a Money value into the acceptable range for the defined currency.

Options

money is a %Money{} struct
opts is a keyword list with the following keys:
- :rounding_mode that defines how the number will be rounded. See Decimal.Context. The default is :half_even which is also known as “banker’s rounding”
- :cash which determines whether the rounding is being applied to an accounting amount or a cash amount. Some currencies, such as the :AUD and :CHF have a cash unit increment minimum which requires a different rounding increment to an arbitrary accounting amount. The default is false.

There are two kinds of rounding applied:

Round to the appropriate number of fractional digits
Apply an appropriate rounding increment. Most currencies round to the same precision as the number of decimal digits, but some such as :AUD and :CHF round to a minimum such as 0.05 when its a cash amount.

Examples

iex> Money.round Money.new("123.7456", :CHF), cash: true
#Money<:CHF, 125>

iex> Money.round Money.new("123.7456", :CHF)
#Money<:CHF, 123.75>

Money.round Money.new("123.7456", :JPY)
#Money<:JPY, 124>

split(money, parts)

split(Money.t(), non_neg_integer()) :: {Money.t(), Money.t()}

Split a Money value into a number of parts maintaining the currency’s precision and rounding and ensuring that the parts sum to the original amount.

Options

money is a %Money{} struct
parts is an integer number of parts into which the money is split

Returns a tuple {dividend, remainder} as the function result derived as follows:

Round the money amount to the required currency precision using Money.round/1
Divide the result of step 1 by the integer divisor
Round the result of the division to the precision of the currency using Money.round/1
Return two numbers: the result of the division and any remainder that could not be applied given the precision of the currency.

Examples

Money.split Money.new(123.5, :JPY), 3
{¥41, ¥1}

Money.split Money.new(123.4, :JPY), 3
{¥41, ¥0}

Money.split Money.new(123.7, :USD), 9
{$13.74, $0.04}

sub(money1, money2)

sub(money_1 :: Money.t(), money_2 :: Money.t()) ::
  {:ok, Money.t()} |
  {:error, {Exception.t(), String.t()}}

Subtract one Money value struct from another.

Options

money_1 and money_2 are any valid Money.t types returned by Money.new/2

Returns

{:ok, money} or
{:error, reason}

Example

iex> Money.sub Money.new(:USD, 200), Money.new(:USD, 100)
{:ok, Money.new(:USD, 100)}

sub!(a, b)

sub!(money_1 :: Money.t(), money_2 :: Money.t()) :: Money.t() | none()

Subtract one Money value struct from another and raise on error.

Returns either {:ok, money} or {:error, reason}.

Options

money_1 and money_2 are any valid Money.t types returned by Money.new/2

Returns

a Money.t struct or
raises an exception

Examples

iex> Money.sub! Money.new(:USD, 200), Money.new(:USD, 100)
#Money<:USD, 100>

Money.sub! Money.new(:USD, 200), Money.new(:CAD, 500)
** (ArgumentError) Cannot subtract monies with different currencies. Received :USD and :CAD.

to_currency(money, to_currency, rates \\ Money.ExchangeRates.latest_rates())

to_currency(Money.t(), Money.currency_code(), Map.t()) ::
  {:ok, Map.t()} |
  {:error, {Exception.t(), String.t()}}

Convert money from one currency to another.

Options

money is any Money.t struct returned by Cldr.Currency.new/2
to_currency is a valid currency code into which the money is converted
rates is a Map of currency rates where the map key is an upcased atom or string and the value is a Decimal conversion factor. The default is the latest available exchange rates returned from Money.ExchangeRates.latest_rates()

Examples

Money.to_currency(Money.new(:USD, 100), :AUD, %{USD: Decimal.new(1), AUD: Decimal.new(0.7345)})
{:ok, #Money<:AUD, 73.4500>}

Money.to_currency(Money.new("USD", 100), "AUD", %{"USD" => Decimal.new(1), "AUD" => Decimal.new(0.7345)})
{:ok, #Money<:AUD, 73.4500>}

iex> Money.to_currency Money.new(:USD, 100) , :AUDD, %{USD: Decimal.new(1), AUD: Decimal.new(0.7345)}
{:error, {Cldr.UnknownCurrencyError, "The currency :AUDD is invalid"}}

iex> Money.to_currency Money.new(:USD, 100) , :CHF, %{USD: Decimal.new(1), AUD: Decimal.new(0.7345)}
{:error, {Money.ExchangeRateError, "No exchange rate is available for currency :CHF"}}

to_currency!(money, currency)

Convert money from one currency to another and raises on error

Options

money is any Money.t struct returned by Cldr.Currency.new/2
to_currency is a valid currency code into which the money is converted
rates is a Map of currency rates where the map key is an upcased atom or string and the value is a Decimal conversion factor. The default is the latest available exchange rates returned from Money.ExchangeRates.latest_rates()

Examples

iex> Money.to_currency! Money.new(:USD, 100) , :AUD, %{USD: Decimal.new(1), AUD: Decimal.new(0.7345)}
#Money<:AUD, 73.4500>

iex> Money.to_currency! Money.new("USD", 100) , "AUD", %{"USD" => Decimal.new(1), "AUD" => Decimal.new(0.7345)}
#Money<:AUD, 73.4500>

Money.to_currency! Money.new(:USD, 100) , :ZZZ, %{USD: Decimal.new(1), AUD: Decimal.new(0.7345)}
** (Cldr.UnknownCurrencyError) Currency :ZZZ is not known

to_currency!(money, currency, rates)

to_decimal(money)

to_decimal(money :: Money.t()) :: Decimal.t()

Returns the amount part of a Money type as a Decimal

Options

money is any valid Money.t type returned by Money.new/2

Returns

a Decimal.t

Example

iex> m = Money.new("USD", 100)
iex> Money.to_decimal(m)
#Decimal<100>

to_integer_exp(money)

Returns a tuple comprising the currency code, integer amount, exponent and remainder

Some services require submission of money items as an integer with an implied exponent that is appropriate to the currency.

Rather than return only the integer, Money.to_integer_exp returns the currency code, integer, exponent and remainder. The remainder is included because to return an integer money with an implied exponent the Money has to be rounded potentially leaving a remainder.

Options

money is any Money.t struct returned by Cldr.Currency.new/2

Notes

Since the returned integer is expected to have the implied fractional digits the Money needs to be rounded which is what this function does.

Example

iex> m = Money.new(:USD, "200.012356")
#Money<:USD, 200.012356>
iex> Money.to_integer_exp(m)
{:USD, 20001, -2, Money.new(:USD, "0.002356")}

iex> m = Money.new(:USD, "200.00")
#Money<:USD, 200.00>
iex> Money.to_integer_exp(m)
{:USD, 20000, -2, Money.new(:USD, "0.00")}

to_string(money, options \\ [])

Returns a formatted string representation of a Money{}.

Formatting is performed according to the rules defined by CLDR. See Cldr.Number.to_string/2 for formatting options. The default is to format as a currency which applies the appropriate rounding and fractional digits for the currency.

Options

money_1 is any valid Money.t type returned by Money.new/2

Returns

{:ok, string} or
{:error, reason}

Examples

iex> Money.to_string Money.new(:USD, 1234)
{:ok, "$1,234.00"}

iex> Money.to_string Money.new(:JPY, 1234)
{:ok, "¥1,234"}

iex> Money.to_string Money.new(:THB, 1234)
{:ok, "THB1,234.00"}

iex> Money.to_string Money.new(:USD, 1234), format: :long
{:ok, "1,234 US dollars"}

to_string!(money, options \\ [])

Returns a formatted string representation of a Money{} or raises if there is an error.

Formatting is performed according to the rules defined by CLDR. See Cldr.Number.to_string!/2 for formatting options. The default is to format as a currency which applies the appropriate rounding and fractional digits for the currency.

Examples

iex> Money.to_string! Money.new(:USD, 1234)
"$1,234.00"

iex> Money.to_string! Money.new(:JPY, 1234)
"¥1,234"

iex> Money.to_string! Money.new(:THB, 1234)
"THB1,234.00"

iex> Money.to_string! Money.new(:USD, 1234), format: :long
"1,234 US dollars"

validate_currency(currency_code)