gno.land/p/moul/x/daily/fraction/v0

Exact rational arithmetic — New, Int, Zero, Add, Sub, Mul, Div, Neg, Cmp, Equal, String, Decimal.

Values are p/q with int64 numerator and denominator, always in lowest terms with a positive denominator.

1import "gno.land/p/moul/x/daily/fraction/v0"
2
3third, _ := fraction.New(1, 3)
4sum, ok := third.Add(third)      // 2/3, ok
5sum, ok = sum.Add(third)         // exactly 1 — not 0.9999…
6fraction.Decimal(third, 5)       // "0.33333"

This exists because there are no floats worth trusting on chain. 0.1 + 0.2 is not 0.3 in binary floating point, and a consensus system cannot afford an answer that depends on rounding. A fraction is exact; it only becomes lossy at the moment you ask for a decimal, and Decimal makes that moment explicit — the caller chooses how much to lose and when.

Overflow is reported, never wrapped. Every operation returns ok=false on int64 overflow rather than silently producing a wrapped numerator, which would be a wrong answer that looks perfectly fine.

Cmp cross-multiplies, so comparison is exact too: 1/3 and 33333/100000 are identical to five decimal places, and it still knows which is larger.

The sign always lives in the numerator, so 1/-2 and -1/2 are the same value. The zero value of the type behaves as 0/1 rather than dividing by zero.

Live demo: r/moul/x/daily/fractiondemo · render it at /r/moul/x/daily/fractiondemo/v0.

Part of moul/gno-contracts — moul's versioned gno.land contracts. See the repository for the full catalog, build/test tooling, and usage.

🧪 Highly experimental — potentially vibe-coded. Not audited; may break, change, or be removed at any time. Do not use with anything of value. Full disclaimer: DISCLAIMER.