Jadpo is experimental and not ready for production. These docs follow the compiler's main branch as of 5 Nov 2026. What's built · Install 0.3.0
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ReferenceMoney and banking

LanguageValues and typesStandard typesMoney and banking

ExchangeRate

On this page

A rate between two currencies at a moment in time.

Use it to record the rate you were given and to convert: money.convert applies one. Jadpo doesn't fetch rates, so your app gets them from a provider.

Shape

Field Type Required?
from Currency Yes
to Currency Yes
rate Decimal Yes
at Instant Yes

Example

example
ExchangeRate { from: Currency.gbp to: Currency.eur rate: 1.17 at: "2026-10-18T09:00:00Z" }

text.parse(raw, as: ExchangeRate) reads one from text that comes from outside. Text that isn't one at all fails malformed, such as GBP/EUR 1.17, GBP-EUR 1.17 2026-10-18T09:00:00Z or GBP/XYZ 1.17 2026-10-18T09:00:00Z.

Good to know

  • It holds when the rate applied, so keep it with what you converted to show later how a figure was reached.
  • == tells you whether two are the same. < and list.sort_by don't take it, so sort by one of its parts instead.

In JSON

An object of its parts, in a request, a response or json.write:

json
{"from":"GBP","to":"EUR","rate":"1.17","at":"2026-10-18T09:00:00Z"}{"from":"EUR","to":"JPY","rate":"162.4031","at":"2026-10-18T09:30:00Z"}

Details

Text form, storage, how it is shown, and operations

ExchangeRate is in the group Money and banking, and has been in Jadpo since 0.1.0.

Text form

text.from writes one standard text form, the same form text.parse reads back: GBP/EUR 1.17 2026-10-18T09:00:00Z and EUR/JPY 162.4031 2026-10-18T09:30:00Z.

How it is stored

It is stored in 4 columns, each named for the field, _ and its suffix. This is EUR/JPY 162.4031 2026-10-18T09:30:00Z:

Column Type Holds
<field>_from char(3) 'EUR'
<field>_to char(3) 'JPY'
<field>_rate numeric 162.4031
<field>_at timestamptz(3) '2026-10-18 09:30:00.000000+00'::timestamptz

How it is shown to people

text.format(value, locale:) shows it to people in their locale.

With locale: Locale.en_gb:

Value Shown
GBP/EUR 1.17 2026-10-18T09:00:00Z GBP/EUR 1.17 2026-10-18T09:00:00Z
EUR/JPY 162.4031 2026-10-18T09:30:00Z EUR/JPY 162.4031 2026-10-18T09:30:00Z

Operations

  • money.convert(value: Money, rate: ExchangeRate) -> Money: value in rate's to currency, from its from one: the major units times rate.rate, rounded half to even to a minor unit, so £10.50 at a GBP/EUR rate of 1.17 is €12.28. It fails with currency_mismatch when value isn't in rate.from, unless that is known: an inverted rate is then a compile error. The rate is one the app holds; nothing here fetches one.

It also takes text.parse, text.from, text.format, json.read, json.write and ==. How every standard type behaves says how they work.

Related

Markdown for agents: /docs/types/type-exchange-rate.md.Built from Jadpo main at aee2e8f.