Reference · Decimals and money

money.compare

money.compare(map, map) -> int

What it does

How two amounts of one currency stand: -1 when the first is smaller, 0 when they are equal, 1 when it is larger. Comparing across currencies is a runtime error, as is adding them. Use it where < and > would be used on numbers: is the balance enough, is the total over the limit.

Examples

let a = money.of("10.25", "USD")let b = money.of("0.75", "USD")print(money.compare(a, b), money.compare(b, a), money.compare(a, a))print(money.compare(a, b) > 0, money.compare(money.of(-1, "USD"), money.zero("USD")))

1 -1 0true -1

Edge cases

• Zeros at the end do not count: 10.25 and 10.250 compare equal.
• A map made by hand or read from JSON compares too, read as money.of reads an amount: an int or numeric text, the code trimmed and in any case. More decimals than the currency has is a runtime error, so 1.005 dollars is never more than 1.00: round it first with money.round.
• For a sort, sort_by on the amount is simpler; money.compare is for one decision.

let a = money.of("10.25", "USD")print(money.compare(a, { amount: "10.250", currency: "usd" }))let enough = money.compare(money.of(50, "USD"), a) >= 0print(enough)print([money.of(3, "USD"), money.of(1, "USD"), money.of(2, "USD")] | sort_by((m) => m.amount) | map((m) => m.amount))

0true[1.00m, 2.00m, 3.00m]

Errors

Two currencies, or a value that is not money (a map with more decimals than its currency has, too), are runtime errors, not error values.

print(money.compare(money.of(1, "USD"), money.of(1, "EUR")))

line 1: cannot compare USD and EUR: convert one currency to the other first

print(money.compare(money.of(1, "USD"), { amount: "1.005", currency: "USD" }))

line 1: `money.compare`: 1.005 has more decimals than USD has (2): round it first with money.round(m, mode)

Chaining

let limit = money.of(100, "USD")print(money.of(120, "USD") | money.compare(limit))print([money.of(120, "USD"), money.of(80, "USD")] | filter((m) => money.compare(m, limit) > 0) | len)

11

See also

money.is_zero, money.sub, money.add, sort_by

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