foundation-money — IMP FORGE

Immutable money type with decimal precision for financial calculations

Tier	foundation
Role	unclassified (baselined)
Path	`crates/foundation/money`
Edition	2021
Targets	foundation_money
Public items	43 across 1 module
Tests	51

What it is for

# foundation-money

Immutable money type with decimal precision for financial calculations.

Core Features

Exact decimal precision: No floating-point errors
Immutability: All operations return new values
Currency enforcement: Operations require matching currencies
Banker's rounding: Fair rounding for financial calculations

Example

use foundation_money::{Money, dec};
use rust_decimal::Decimal;

// Create money values
let price = Money::usd(dec!(19.99));
let quantity = Decimal::from(3);
let subtotal = price * quantity;  // $59.97

// Tax calculation with quantization
let tax_rate = dec!(0.0825);  // 8.25%
let tax = (subtotal * tax_rate).quantized();  // Rounds to $4.95

// Currency safety - this would return an error:
// let usd = Money::usd(dec!(100));
// let eur = Money::eur(dec!(100));
// let sum = (usd + eur)?;  // CurrencyMismatch error

Capabilities

`Decimal`

# foundation-money

Item
`Decimal :: fn mul(self, money : Money) -> Self::Output`

`Money:Money`

# foundation-money

Item
`pub struct Money`

`Money:abs`

# foundation-money

Item
`Money :: fn abs(& self) -> Self`

`Money:add`

# foundation-money

Item
`Money :: fn add(self, other : Self) -> Self::Output`

`Money:amount`

# foundation-money

Item
`Money :: fn amount(& self) -> Decimal`

`Money:aud`

# foundation-money

Item
`Money :: fn aud(amount : Decimal) -> Self`

`Money:btc`

# foundation-money

Item
`Money :: fn btc(amount : Decimal) -> Self`

`Money:cad`

# foundation-money

Item
`Money :: fn cad(amount : Decimal) -> Self`

`Money:chf`

# foundation-money

Item
`Money :: fn chf(amount : Decimal) -> Self`

`Money:cny`

# foundation-money

Item
`Money :: fn cny(amount : Decimal) -> Self`

`Money:currency`

# foundation-money

Item
`Money :: fn currency(& self) -> & 'static str`

`Money:decimals`

# foundation-money

Item
`Money :: fn decimals(& self) -> u32`

`Money:deserialize`

# foundation-money

Item
`Money :: fn deserialize <D>(deserializer : D) -> Result <Self, D::Error> where D : Deserializer <'de>,`

`Money:eq`

# foundation-money

Item
`Money :: fn eq(& self, other : & Self) -> bool`

`Money:eur`

# foundation-money

Item
`Money :: fn eur(amount : Decimal) -> Self`

`Money:fmt`

# foundation-money

Item
`Money :: fn fmt(& self, f : & mut fmt::Formatter <'_>) -> fmt::Result`

`Money:gbp`

# foundation-money

Item
`Money :: fn gbp(amount : Decimal) -> Self`

`Money:hash`

# foundation-money

Item
`Money :: fn hash <H : Hasher>(& self, state : & mut H)`

`Money:is`

# foundation-money

Item
`Money :: fn is_positive(& self) -> bool`
`Money :: fn is_negative(& self) -> bool`
`Money :: fn is_zero(& self) -> bool`

`Money:jpy`

# foundation-money

Item
`Money :: fn jpy(amount : Decimal) -> Self`

`Money:krw`

# foundation-money

Item
`Money :: fn krw(amount : Decimal) -> Self`

`Money:mul`

# foundation-money

Item
`Money :: fn mul(self, scalar : Decimal) -> Self::Output`
`Money :: fn mul(self, scalar : i32) -> Self::Output`
`Money :: fn mul(self, scalar : i64) -> Self::Output`

`Money:mxn`

# foundation-money

Item
`Money :: fn mxn(amount : Decimal) -> Self`

`Money:neg`

# foundation-money

Item
`Money :: fn neg(self) -> Self::Output`

`Money:new`

# foundation-money

Item
`Money :: fn new(amount : Decimal, currency : & 'static str) -> Self`

`Money:quantized`

# foundation-money

Item
`Money :: fn quantized(& self) -> Self`

`Money:same`

# foundation-money

Item
`Money :: fn same_currency(& self, other : & Self) -> bool`

`Money:serialize`

# foundation-money

Item
`Money :: fn serialize <S>(& self, serializer : S) -> Result <S::Ok, S::Error> where S : Serializer,`

`Money:sub`

# foundation-money

Item
`Money :: fn sub(self, other : Self) -> Self::Output`

`Money:try`

# foundation-money

Item
`Money :: fn try_add(& self, other : & Self) -> Result <Self, MoneyError>`
`Money :: fn try_sub(& self, other : & Self) -> Result <Self, MoneyError>`
`Money :: fn try_cmp(& self, other : & Self) -> Result <Ordering, MoneyError>`

`Money:usd`

# foundation-money

Item
`Money :: fn usd(amount : Decimal) -> Self`

`Money:zero`

# foundation-money

Item
`Money :: fn zero(currency : & 'static str) -> Self`

`MoneyError`

# foundation-money

Item
`pub enum MoneyError`
`MoneyError :: fn currency_mismatch(operation : & 'static str, left : & str, right : & str) -> Self`

`i32`

# foundation-money

Item
`i32 :: fn mul(self, money : Money) -> Self::Output`

`i64`

# foundation-money

Item
`i64 :: fn mul(self, money : Money) -> Self::Output`

`currency_decimals (other)`

_No module-level documentation is present in the source._

Item
`fn get(currency : & str) -> u32`

How to use it

From this crate's own rustdoc:

use foundation_money::{Money, dec};
use rust_decimal::Decimal;

// Create money values
let price = Money::usd(dec!(19.99));
let quantity = Decimal::from(3);
let subtotal = price * quantity;  // $59.97

// Tax calculation with quantization
let tax_rate = dec!(0.0825);  // 8.25%
let tax = (subtotal * tax_rate).quantized();  // Rounds to $4.95

// Currency safety - this would return an error:
// let usd = Money::usd(dec!(100));
// let eur = Money::eur(dec!(100));
// let sum = (usd + eur)?;  // CurrencyMismatch error

Module structure

foundation_money

currency_decimals

Public surface

`crate root`

Item	What it is
`pub enum MoneyError`	Money-related errors.
`MoneyError :: fn currency_mismatch(operation : & 'static str, left : & str, right : & str) -> Self`	Create a currency mismatch error.
`pub struct Money`	An immutable monetary amount with currency
`Money :: fn serialize <S>(& self, serializer : S) -> Result <S::Ok, S::Error> where S : Serializer,`	—
`Money :: fn deserialize <D>(deserializer : D) -> Result <Self, D::Error> where D : Deserializer <'de>,`	—
`Money :: fn new(amount : Decimal, currency : & 'static str) -> Self`	Create a new Money value
`Money :: fn usd(amount : Decimal) -> Self`	Create a Money value in USD.
`Money :: fn eur(amount : Decimal) -> Self`	Create a Money value in EUR.
`Money :: fn gbp(amount : Decimal) -> Self`	Create a Money value in GBP.
`Money :: fn jpy(amount : Decimal) -> Self`	Create a Money value in JPY.
`Money :: fn mxn(amount : Decimal) -> Self`	Create a Money value in MXN.
`Money :: fn cad(amount : Decimal) -> Self`	Create a Money value in CAD.
`Money :: fn aud(amount : Decimal) -> Self`	Create a Money value in AUD.
`Money :: fn chf(amount : Decimal) -> Self`	Create a Money value in CHF.
`Money :: fn cny(amount : Decimal) -> Self`	Create a Money value in CNY.
`Money :: fn krw(amount : Decimal) -> Self`	Create a Money value in KRW.
`Money :: fn btc(amount : Decimal) -> Self`	Create a Money value in BTC.
`Money :: fn zero(currency : & 'static str) -> Self`	Create a zero Money value in the given currency.
`Money :: fn amount(& self) -> Decimal`	Get the amount.
`Money :: fn currency(& self) -> & 'static str`	Get the currency code.
`Money :: fn decimals(& self) -> u32`	Get the number of decimal places for this currency.
`Money :: fn is_positive(& self) -> bool`	Check if the amount is positive (> 0).
`Money :: fn is_negative(& self) -> bool`	Check if the amount is negative (< 0).
`Money :: fn is_zero(& self) -> bool`	Check if the amount is zero.
`Money :: fn abs(& self) -> Self`	Get the absolute value.
`Money :: fn quantized(& self) -> Self`	Round to the currency's decimal places using banker's rounding
`Money :: fn same_currency(& self, other : & Self) -> bool`	Check if this money has the same currency as another.
`Money :: fn try_add(& self, other : & Self) -> Result <Self, MoneyError>`	Try to add two Money values (requires matching currencies)
`Money :: fn try_sub(& self, other : & Self) -> Result <Self, MoneyError>`	Try to subtract two Money values (requires matching currencies)
`Money :: fn try_cmp(& self, other : & Self) -> Result <Ordering, MoneyError>`	Compare two Money values (requires matching currencies)
`Money :: fn fmt(& self, f : & mut fmt::Formatter <'_>) -> fmt::Result`	—
`Money :: fn eq(& self, other : & Self) -> bool`	—
`Money :: fn hash <H : Hasher>(& self, state : & mut H)`	—
`Money :: fn add(self, other : Self) -> Self::Output`	—
`Money :: fn sub(self, other : Self) -> Self::Output`	—
`Money :: fn neg(self) -> Self::Output`	—
`Money :: fn mul(self, scalar : Decimal) -> Self::Output`	—
`Decimal :: fn mul(self, money : Money) -> Self::Output`	—
`Money :: fn mul(self, scalar : i32) -> Self::Output`	—
`i32 :: fn mul(self, money : Money) -> Self::Output`	—
`Money :: fn mul(self, scalar : i64) -> Self::Output`	—
`i64 :: fn mul(self, money : Money) -> Self::Output`	—

`currency_decimals`

Item	What it is
`fn get(currency : & str) -> u32`	Get the number of decimal places for a currency.

Re-exports. Exported here, defined elsewhere.

Export	Defined in
`dec`	`rust_decimal_macros::dec`

Boundary

Depends on no other workspace tier.

Shares tier foundation with 27 other crates: foundation-audit-log, foundation-basemodels, foundation-bounded-io, foundation-conversation-closure, foundation-crypto-sign, foundation-decisioning, foundation-encounter-vocabulary, foundation-fs-metadata, … (27 total).

_What this crate deliberately does NOT own is a judgment. No committed registry records one for it, so none is stated here._

Where it sits

Tier (ontology)	`foundation`
Architectural role (taxonomy)	`unclassified (baselined)`
Location	`crates/foundation/money`
Vocabulary in force (lexicon)	`current`

Dependencies

Runtime, from outside the workspace.

Crate	Requirement	Features	Optional	Only on
`rust_decimal`	`^1.36`	`serde`	no	always
`rust_decimal_macros`	`^1`	—	no	always
`serde`	`^1`	`derive`	no	always
`serde_json`	`^1`	—	no	always
`thiserror`	`^2`	—	no	always

Development, from outside the workspace.

Crate	Requirement	Features	Optional	Only on
`tokio-test`	`^0.4`	—	no	always

Build. None.

Depended on by. 12 workspace crates.

Signal flow — what reaches this crate, and what it reaches.

flowchart LR
  n_application_conversation["application-conversation"] -->|uses| SELF
  n_application_crm["application-crm"] -->|uses| SELF
  n_application_money["application-money"] -->|uses| SELF
  n_domain_billing["domain-billing"] -->|uses| SELF
  n_domain_catalog["domain-catalog"] -->|uses| SELF
  n_domain_crm["domain-crm"] -->|uses| SELF
  n_domain_ledger["domain-ledger"] -->|uses| SELF
  n_domain_legal_matter["domain-legal-matter"] -->|uses| SELF
  n_domain_pricing_rules["domain-pricing-rules"] -->|uses| SELF
  n_operations_control_plane["operations-control-plane"] -->|uses| SELF
  n_platform_privacy_scan_api["platform-privacy-scan-api"] -->|uses| SELF
  n_tools_corpus["tools-corpus"] -->|uses| SELF
  SELF["foundation-money"]
  classDef self fill:#1f883d,stroke:#1f883d,color:#fff;
  class SELF self;

Feature flags

Feature	Enables	On by default
`default`	—	yes

flowchart LR
  n_default["default"]

Targets

Kind	Name	Source
lib	`foundation_money`	`src/lib.rs`

Error model

Error type	Named by
`MoneyError`	declared, no public signature returns it

Operational characteristics

Property	Evidence
async public surface	none detected
async runtime	none detected
database access	none detected
network I/O	none detected
unsafe code	none detected
environment variables	none detected

No unsafe block, unsafe fn, unsafe impl or unsafe trait was found by the parser anywhere in this crate's source.

Configuration

No environment variable is read with a literal name anywhere in this crate. A variable whose key is computed at run time cannot be listed here, and is not claimed to be absent.

12 workspace crates depend on this one: application-conversation, application-crm, application-money, domain-billing, domain-catalog, domain-crm, domain-ledger, domain-legal-matter, domain-pricing-rules, operations-control-plane, platform-privacy-scan-api, tools-corpus.

Verification

Kind	Count
Unit tests	51
Integration tests	0
Examples	0
Doctests	1

Evidence by module. How often each public module is named by something executable.

Module	Tests	Examples	Consumers
`crate root`	2	0	9
`currency_decimals`	1	0	7

What the tests establish, by name:

test_abs — src/lib.rs
test_add_same_currency — src/lib.rs
test_bankers_rounding — src/lib.rs
test_bill_split — src/lib.rs
test_create_money — src/lib.rs
test_currency_constructors — src/lib.rs
test_currency_conversion_workflow — src/lib.rs
test_currency_decimals — src/lib.rs
test_currency_decimals_contract — src/lib.rs
test_discount — src/lib.rs
test_display — src/lib.rs
test_equality — src/lib.rs
test_equality_different_currency — src/lib.rs
test_error_message_add — src/lib.rs
test_error_message_compare — src/lib.rs
test_error_message_subtract — src/lib.rs
test_hash — src/lib.rs
test_hash_observes_amount_and_currency — src/lib.rs
test_immutability — src/lib.rs
test_is_negative — src/lib.rs
test_is_positive — src/lib.rs
test_is_zero — src/lib.rs
test_money_decimals — src/lib.rs
test_multiply_by_decimal — src/lib.rs
test_multiply_by_i32 — src/lib.rs
test_multiply_by_i64 — src/lib.rs
test_multiply_decimal_by_money — src/lib.rs
test_multiply_i32_by_money — src/lib.rs
test_negate — src/lib.rs
test_negative_results — src/lib.rs
_… 21 more_

Documentation coverage

Measure	Documented	Total
Public items with rustdoc	29	43
Public modules with a `//!` block	0	1

pie showData
    title Public items with rustdoc
    "Documented" : 29
    "No rustdoc detected" : 14

Metrics

Metric	Value
Rust source files	1
Source lines	1012
Code lines	687
Public API items	43
Public modules	1
Tests	51
Examples	0
Cargo features	1
Direct runtime dependencies	5
Workspace reverse dependencies	12

pie showData
    title Public API by kind
    "enum" : 1
    "function" : 1
    "method" : 40
    "struct" : 1

pie showData
    title Rust source composition
    "Code" : 687
    "Blank or comment" : 325

Generation

Rendered by tools-corpus corpus readme from repository evidence alone, renderer schema 2, lexicon current. No model, network service or database was consulted. Regenerate with tools-corpus corpus readme --write; verify with --check.

What it is for

Core Features

Example

Capabilities

Decimal

Money:Money

Money:abs

Money:add

Money:amount

Money:aud

Money:btc

Money:cad

Money:chf

Money:cny

Money:currency

Money:decimals

Money:deserialize

Money:eq

Money:eur

Money:fmt

Money:gbp

Money:hash

Money:is

Money:jpy

Money:krw

Money:mul

Money:mxn

Money:neg

Money:new

Money:quantized

Money:same

Money:serialize

Money:sub

Money:try

Money:usd

Money:zero

MoneyError

i32

i64

currency_decimals (other)

How to use it

Module structure

Public surface

Boundary

Where it sits

Dependencies

Feature flags

Targets

Error model

Operational characteristics

Configuration

Related capabilities

Verification

Documentation coverage

Metrics

Generation

`Decimal`

`Money:Money`

`Money:abs`

`Money:add`

`Money:amount`

`Money:aud`

`Money:btc`

`Money:cad`

`Money:chf`

`Money:cny`

`Money:currency`

`Money:decimals`

`Money:deserialize`

`Money:eq`

`Money:eur`

`Money:fmt`

`Money:gbp`

`Money:hash`

`Money:is`

`Money:jpy`

`Money:krw`

`Money:mul`

`Money:mxn`

`Money:neg`

`Money:new`

`Money:quantized`

`Money:same`

`Money:serialize`

`Money:sub`

`Money:try`

`Money:usd`

`Money:zero`

`MoneyError`

`i32`

`i64`

`currency_decimals (other)`