yield-amm

yield-amm is an AMM purpose-built for trading a principal token (PT) against its underlying. The invariant $x \cdot y^t = k$ makes prices converge to 1:1 as time-to-maturity $t$ approaches 0.

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Accounts

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Pool

["pool", market].

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Pool methods

• time_factor(now) = clamp((maturity - now) / total_duration, 0, 1).
• compute_k(t) = underlying_reserves × pt_reserves^t.
• get_pt_out(underlying_in, t), solve k / (x + amount_in) for the exponent $t$.
• get_underlying_out(pt_in, t), inverse.

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Instructions

Swap is disabled within t < 0.001 of maturity to avoid exponent blow-up. At that point PT is essentially at par, just call redeem_pt on the split engine.

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Math helpers (kimia-math)

• pow_frac(base, exponent), exp(exponent × ln(base)) via range-reduced Taylor series. Error < 0.05%.
• mul_fp, div_fp, u128-intermediate fixed-point ops, always rounds down.

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Errors

SwapDisabledNearMaturity, SlippageExceeded, InsufficientLiquidity, MathOverflow, AlreadyMatured.

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