gno.land/p/nym-moultest123/xmath

Max, Min, Clamp, Abs and Sign for every built-in numeric type, one concrete function per type. Gno has no generics, so the alternative is writing the same three-line helper again in each realm.

1xmath.MaxInt(3, 7)             // 7
2xmath.ClampInt64(x, 0, 100)    // x, bounded to [0,100]
3xmath.AbsFloat64(-2.5)         // 2.5
4xmath.SignInt(-9)              // -1

Unsigned types get no Abs or Sign: both are trivially themselves and 1, and offering them would only invite an overflow bug at the call site.

The name is the type suffix: MaxInt8, MinUint64, ClampFloat32.

Sign returns -1, 0 or 1. Clamp does not validate its bounds: calling it with min > max returns one bound or the other depending on the value, so check the bounds yourself if they are computed.

Generated

xmath.gen.gno and xmath.gen_test.gno are written by tools/xmathgen and carry a DO NOT EDIT header. Edit the generator, never the output:

1go -C tools run ./xmathgen           # rewrite both files
2go -C tools run ./xmathgen -check    # fail if they are stale

Adding a type is one row in the types table in tools/xmathgen/main.go; it expands to 5 functions plus their tests.

The header used to name a generator.go that was never committed, so it was a rule nobody could follow. The generator above was reconstructed from the output it describes and reproduces both committed files byte for byte, which go test ./tools/xmathgen asserts on every run.

MulDiv: the proportional share, through a 128-bit intermediate

Hand-written rather than generated, in muldiv.gno, because it is one function and not a per-type family.

1xmath.MulDiv(pot, stake, total)    // this stake's cut, rounded toward zero
2xmath.MulDivUp(pot, stake, total)  // the same ratio, rounded away from zero

a*b/c computes a*b first, and an int64 product that does not fit wraps silently to a plausible number. Measured with a = 2^62, b = 4, c = 8: the true share is 2305843009213693952 and the naive form answers 0, because 2^62 * 4 is exactly 2^64 and wraps to zero. Nothing fails, nothing logs, and a payout split is simply wrong.

Ten realms deployed on gnoland-1 carry their own copy of this, all reaching for math/bits the same way: bubblerumble (several versions) and kourt, whose mulDiv128 is the same function with its own panic strings. It had no owner in p/moul or p/nt until now.

MulDiv panics rather than returning a wrong number: on a negative operand, on a denominator at or below zero, and on a quotient that does not fit.

MulDivUp exists because rounding is a money question, not a style one. Rounding a fee down and a payout up is how a pool pays out more than it holds. Use MulDiv for what someone receives and MulDivUp for what someone owes; TestRoundingDirectionIsTheMoneyQuestion pins that they never differ by more than one and never cross.

Adding these is a non-breaking change, so xmath stays at its current version and every existing importer is untouched.

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

⚠️ Disclaimer: provided as-is, without warranty; not security-audited. Full disclaimer: DISCLAIMER.