Discount

An amount off a price or a percentage off it, a choice: money.apply_discount takes one off a Price. An amount off is never below 0, and a percentage off is from 0% to 100%.

Money and banking; not ordered; since Jadpo 0.1.0.

Make one

Pick one of its variants and give its fields, Discount.amount_off { amount: ... }.

Variants

Text, JSON and storage

It has no single text form, so text.from and text.parse don't take it. JSON sends an object of its variant's name, as tag, and the variant's fields.

It is stored in 4 columns, each named for the field, _ and its suffix. This is {"tag":"percentage_off","percentage":"20%"}:

Shown to people

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

With locale: Locale.en_gb:

Operations

• money.apply_discount(price: Price, discount: Discount) -> Price: price with discount taken off its amount, keeping whether it includes tax: an amount off in the price's currency, or that percentage of the amount, rounded half to even to a minor unit, so 15% off £10.05 is £1.51 off. More off than the price leaves nothing. It fails with currency_mismatch for an amount off in another currency.

Like every standard type, it also has the contract's own operations: text.format, json.read, json.write and ==. It isn't ordered, so < and sorting don't take it. Every standard type meets one contract says how they work.