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Package ledger is gnosplit's arithmetic: amounts in cents, how an expense is split, and the fewest transfers that set...

Overview

Package ledger is gnosplit's arithmetic: amounts in cents, how an expense is split, and the fewest transfers that settle a group. It holds no state, so a later gnosplit release and an app can reuse it as is.

Constants 2

const MaxCents 

1const MaxCents int64 = 10_000_000_000
source

MaxCents bounds one amount: 100 million units of a currency. With rates up to MaxRate the products below stay far inside int64.

const MaxRate 

1const MaxRate int64 = 1_000_000_000_000
source

MaxRate bounds a conversion rate, in millionths: 1,000,000 units for one.

Functions 9

func Convert 

1func Convert(cents, rate int64) int64
source

Convert turns cents into cents of another currency at rate (millionths), rounding half up. It splits the rate so no product overflows.

func Equal 

1func Equal(total int64, n int) []int64
source

Equal splits total into n parts that differ by at most one cent; the first total%n parts take the extra cent. A negative total (money received) splits the same way, every part negative.

func Format 

1func Format(cents int64) string
source

Format writes cents as "1,234.56", "-12.00" or "0.00".

func ParseAmount 

1func ParseAmount(s string) (cents int64, note string, ok bool)
source

ParseAmount reads an amount in the group's currency ("42.50"), or a foreign one with its rate ("50 USD x0.92": 50 dollars at 0.92 each). note is the foreign amount as typed, cleaned up, and "" for a plain one.

func ParseCents 

1func ParseCents(s string) (int64, bool)
source

ParseCents reads a positive amount written "42", "42.5" or "42,50": digits, then at most one "." or "," and two decimals. Thousands separators are refused, since "1,234" would read as 1.234.

func ParseRate 

1func ParseRate(s string) (int64, bool)
source

ParseRate reads a positive rate with up to six decimals, in millionths.

func Signed 

1func Signed(cents int64) string
source

Signed is Format with a "+" on positive amounts, for balances.

func Weighted 

1func Weighted(total int64, weights []int64) []int64
source

Weighted splits total in proportion to weights, all positive, by largest remainder: each part is rounded down, then the cents left go to the largest remainders, ties to the first. The parts always sum to total.

func Settle 

1func Settle(balances []int64) []Transfer
source

Settle returns the transfers that bring every balance to zero (balances sum to zero; > 0 means the group owes that member). The largest debt pays the largest credit, ties to the lower index, so each step clears at least one member: at most n-1 transfers, in O(n²) for the few members of a group.

Types 1

type Transfer

struct 
1type Transfer struct {
2	From, To int
3	Amount   int64
4}
source

Transfer is one payment that settles part of a group: From pays To.

Dependencies

Imports 2

/p/nym-alexiscolin000/gnosplit/ledger/v0

Imported by indexer

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Source Files 3