(impl-trait .trait-ownable.ownable-trait)
;; simple-equation
;; simple-equation implements 50:50 weighted-equation-v1-01 (i.e. uniswap)
;; implementation of Balancer WeightedMath (https://github.com/balancer-labs/balancer-monorepo/blob/master/pkg/pool-weighted/contracts/WeightedMath.sol)
;; constants
;;
(define-constant ERR-NOT-AUTHORIZED (err u1000))
(define-constant ERR-NO-LIQUIDITY (err u2002))
(define-constant ERR-WEIGHT-SUM (err u4000))
(define-constant ERR-MAX-IN-RATIO (err u4001))
(define-constant ERR-MAX-OUT-RATIO (err u4002))
(define-data-var contract-owner principal tx-sender)
;; max in/out as % of liquidity
(define-data-var MAX-IN-RATIO uint (* u1 (pow u10 u6))) ;; 1%
(define-data-var MAX-OUT-RATIO uint (* u1 (pow u10 u6))) ;; 1%
;; @desc get-contract-owner
;; @returns principal
(define-read-only (get-contract-owner)
(ok (var-get contract-owner))
)
;; @desc set-contract-owner
;; @param new-contract-owner; new contract-owner
;; @returns (response bool uint)
(define-public (set-contract-owner (new-contract-owner principal))
(begin
(try! (check-is-owner))
(ok (var-set contract-owner new-contract-owner))
)
)
(define-private (check-is-owner)
(ok (asserts! (is-eq tx-sender (var-get contract-owner)) ERR-NOT-AUTHORIZED))
)
;; @desc get-max-in-ratio
;; @returns uint
(define-read-only (get-max-in-ratio)
(var-get MAX-IN-RATIO)
)
;; @desc set-max-in-ratio
;; @param new-max-in-ratio; new MAX-IN-RATIO
;; @returns (response bool)
(define-public (set-max-in-ratio (new-max-in-ratio uint))
(begin
(try! (check-is-owner))
;; MI-03
(asserts! (and (> new-max-in-ratio u0) (< new-max-in-ratio ONE_8)) ERR-MAX-IN-RATIO)
(ok (var-set MAX-IN-RATIO new-max-in-ratio))
)
)
;; @desc get-max-out-ratio
;; @returns unit
(define-read-only (get-max-out-ratio)
(var-get MAX-OUT-RATIO)
)
;; @desc set-max-out-ratio
;; @param new-max-out-ratio; new MAX-OUT-RATIO
;; @returns (response bool uint)
(define-public (set-max-out-ratio (new-max-out-ratio uint))
(begin
(try! (check-is-owner))
;; MI-03
(asserts! (and (> new-max-out-ratio u0) (< new-max-out-ratio ONE_8)) ERR-MAX-OUT-RATIO)
(ok (var-set MAX-OUT-RATIO new-max-out-ratio))
)
)
;; @desc get-invariant
;; @desc invariant = b_x * b_y
;; @param balance-x; balance of token-x
;; @param balance-y; balance of token-y
;; @returns (response uint uint)
(define-read-only (get-invariant (balance-x uint) (balance-y uint))
(ok (pow-down (mul-down balance-x balance-y) u50000000))
)
;; @desc get-y-given-x
;; @desc d_y = dy
;; @desc b_y = balance-y
;; @desc b_x = balance-x / / b_x \ \
;; @desc d_x = dx d_y = b_y * | 1 - | --------------------------- | |
;; @desc w_x = weight-x \ \ ( b_x + d_x ) / /
;; @desc w_y = weight-y
;; @param balance-x; balance of token-x
;; @param balance-y; balance of token-y
;; @param weight-x; weight of token-x
;; @param weight-y; weight of token-y
;; @param dx; amount of token-x added
;; @returns (response uint uint)
(define-read-only (get-y-given-x (balance-x uint) (balance-y uint) (dx uint))
(begin
(asserts! (< dx (mul-down balance-x (var-get MAX-IN-RATIO))) ERR-MAX-IN-RATIO)
(let
(
(dy (div-down (mul-down balance-y dx) (+ balance-x dx)))
)
(asserts! (< dy (mul-down balance-y (var-get MAX-OUT-RATIO))) ERR-MAX-OUT-RATIO)
(ok dy)
)
)
)
;; @desc d_y = dy
;; @desc b_y = balance-y
;; @desc b_x = balance-x / / b_y \ \
;; @desc d_x = dx d_x = b_x * | 1 - | -------------------------- | |
;; @desc w_x = weight-x \ \ ( b_y + d_y ) / /
;; @desc w_y = weight-y
;; @param balance-x; balance of token-x
;; @param balance-y; balance of token-y
;; @param weight-x; weight of token-x
;; @param weight-y; weight of token-y
;; @param dy; amount of token-y added
;; @returns (response uint uint)
(define-read-only (get-x-given-y (balance-x uint) (balance-y uint) (dy uint))
(begin
(asserts! (< dy (mul-down balance-y (var-get MAX-OUT-RATIO))) ERR-MAX-OUT-RATIO)
(let
(
(dx (div-down (mul-down balance-x dy) (+ balance-y dy)))
)
(asserts! (< dx (mul-down balance-x (var-get MAX-IN-RATIO))) ERR-MAX-IN-RATIO)
(ok dx)
)
)
)
;; @desc d_y = dy
;; @desc b_y = balance-y
;; @desc b_x = balance-x / / b_y \ \
;; @desc d_x = dx d_x = b_x * | | -------------------------- | - 1 |
;; @desc w_x = weight-x \ \ ( b_y - d_y ) / /
;; @desc w_y = weight-y
;; @param balance-x; balance of token-x
;; @param balance-y; balance of token-y
;; @param weight-x; weight of token-x
;; @param weight-y; weight of token-y
;; @param dy; amount of token-y added
;; @returns (response uint uint)
(define-read-only (get-x-in-given-y-out (balance-x uint) (balance-y uint) (dy uint))
(begin
(asserts! (< dy (mul-down balance-y (var-get MAX-OUT-RATIO))) ERR-MAX-OUT-RATIO)
(let
(
(dx (div-down (mul-down balance-x dy) (- balance-y dy)))
)
(asserts! (< dx (mul-down balance-x (var-get MAX-IN-RATIO))) ERR-MAX-IN-RATIO)
(ok dx)
)
)
)
;; @desc d_y = dy
;; @desc b_y = balance-y
;; @desc b_x = balance-x / / b_x \ \
;; @desc d_x = dx d_y = b_y * | | -------------------------- | - 1 |
;; @desc w_x = weight-x \ \ ( b_x - d_x ) / /
;; @desc w_y = weight-y
;; @param balance-x; balance of token-x
;; @param balance-y; balance of token-y
;; @param weight-x; weight of token-x
;; @param weight-y; weight of token-y
;; @param dy; amount of token-y added
;; @returns (response uint uint)
(define-read-only (get-y-in-given-x-out (balance-x uint) (balance-y uint) (dx uint))
(begin
(asserts! (< dx (mul-down balance-x (var-get MAX-IN-RATIO))) ERR-MAX-IN-RATIO)
(let
(
(dy (div-down (mul-down balance-y dx) (- balance-x dx)))
)
(asserts! (< dy (mul-down balance-y (var-get MAX-OUT-RATIO))) ERR-MAX-OUT-RATIO)
(ok dy)
)
)
)
;; @desc d_x = dx
;; @desc d_y = dy
;; @desc b_x = balance-x
;; @desc b_y = balance-y
;; @desc spot = b_y / b_x
;; @desc d_x = b_x * ((spot / price) ^ 0.5 - 1)
;; @param balance-x; balance of token-x
;; @param balance-y; balance of token-y
;; @param price; target price
;; @returns (response uint uint)
(define-read-only (get-x-given-price (balance-x uint) (balance-y uint) (price uint))
(let
(
(spot (div-down balance-y balance-x))
(power (pow-down (div-down spot price) u50000000))
)
(asserts! (< price spot) ERR-NO-LIQUIDITY)
(ok (mul-down balance-x (if (<= power ONE_8) u0 (- power ONE_8))))
)
)
;; @desc follows from get-x-given-price
;; @desc d_y = b_y * ((price / spot) ^ 0.5 - 1)
;; @param balance-x; balance of token-x
;; @param balance-y; balance of token-y
;; @param price; target price
;; @returns (response uint uint)
(define-read-only (get-y-given-price (balance-x uint) (balance-y uint) (price uint))
(let
(
(spot (div-down balance-y balance-x))
(power (pow-down (div-down price spot) u50000000))
)
(asserts! (> price spot) ERR-NO-LIQUIDITY)
(ok (mul-down balance-y (if (<= power ONE_8) u0 (- power ONE_8))))
)
)
;; @desc get-token-given-position
;; @param balance-x; balance of token-x
;; @param balance-y; balance of token-y
;; @param total-supply; total supply of pool tokens
;; @param dx; amount of token-x added
;; @param dy; amount of token-y added
;; @returns (response (tutple uint uint) uint)
(define-read-only (get-token-given-position (balance-x uint) (balance-y uint) (total-supply uint) (dx uint) (dy uint))
(ok
(if (is-eq total-supply u0)
{token: (unwrap-panic (get-invariant dx dy)), dy: dy}
{token: (div-down (mul-down total-supply dx) balance-x), dy: (div-down (mul-down balance-y dx) balance-x)}
)
)
)
;; @desc get-position-given-mint
;; @param balance-x; balance of token-x
;; @param balance-y; balance of token-y
;; @param total-supply; total supply of pool tokens
;; @param token; amount of pool token minted
;; @returns (response (tuple uint uint) uint)
(define-read-only (get-position-given-mint (balance-x uint) (balance-y uint) (total-supply uint) (token uint))
(begin
(asserts! (> total-supply u0) ERR-NO-LIQUIDITY)
(ok {dx: (div-down (mul-down balance-x token) total-supply), dy: (div-down (mul-down balance-y token) total-supply)})
)
)
;; @desc get-position-given-burn
;; @param balance-x; balance of token-x
;; @param balance-y; balance of token-y
;; @param total-supply; total supply of pool tokens
;; @param token; amount of pool token to be burnt
;; @returns (response (tuple uint uint) uint)
(define-read-only (get-position-given-burn (balance-x uint) (balance-y uint) (total-supply uint) (token uint))
(get-position-given-mint balance-x balance-y total-supply token)
)
;; math-fixed-point
;; Fixed Point Math
;; following https://github.com/balancer-labs/balancer-monorepo/blob/master/pkg/solidity-utils/contracts/math/FixedPoint.sol
;; constants
;;
(define-constant ONE_8 u100000000) ;; 8 decimal places
;; TODO: this needs to be reviewed/updated
;; With 8 fixed digits you would have a maximum error of 0.5 * 10^-8 in each entry,
;; which could aggregate to about 8 x 0.5 * 10^-8 = 4 * 10^-8 relative error
;; (i.e. the last digit of the result may be completely lost to this error).
(define-constant MAX_POW_RELATIVE_ERROR u4)
;; public functions
;;
;; @desc scale-up
;; @params a
;; @returns uint
(define-read-only (scale-up (a uint))
(* a ONE_8)
)
;; @desc scale-down
;; @params a
;; @returns uint
(define-read-only (scale-down (a uint))
(/ a ONE_8)
)
;; @desc mul-down
;; @params a
;; @params b
;; @returns uint
(define-read-only (mul-down (a uint) (b uint))
(/ (* a b) ONE_8)
)
;; @desc mul-up
;; @params a
;; @params b
;; @returns uint
(define-read-only (mul-up (a uint) (b uint))
(let
(
(product (* a b))
)
(if (is-eq product u0)
u0
(+ u1 (/ (- product u1) ONE_8))
)
)
)
;; @desc div-down
;; @params a
;; @params b
;; @returns uint
(define-read-only (div-down (a uint) (b uint))
(if (is-eq a u0)
u0
(/ (* a ONE_8) b)
)
)
;; @desc div-up
;; @params a
;; @params b
;; @returns uint
(define-read-only (div-up (a uint) (b uint))
(if (is-eq a u0)
u0
(+ u1 (/ (- (* a ONE_8) u1) b))
)
)
;; @desc pow-down
;; @params a
;; @params b
;; @returns uint
(define-read-only (pow-down (a uint) (b uint))
(let
(
(raw (unwrap-panic (pow-fixed a b)))
(max-error (+ u1 (mul-up raw MAX_POW_RELATIVE_ERROR)))
)
(if (< raw max-error)
u0
(- raw max-error)
)
)
)
;; @desc pow-up
;; @params a
;; @params b
;; @returns uint
(define-read-only (pow-up (a uint) (b uint))
(let
(
(raw (unwrap-panic (pow-fixed a b)))
(max-error (+ u1 (mul-up raw MAX_POW_RELATIVE_ERROR)))
)
(+ raw max-error)
)
)
;; math-log-exp
;; Exponentiation and logarithm functions for 8 decimal fixed point numbers (both base and exponent/argument).
;; Exponentiation and logarithm with arbitrary bases (x^y and log_x(y)) are implemented by conversion to natural
;; exponentiation and logarithm (where the base is Euler's number).
;; Reference: https://github.com/balancer-labs/balancer-monorepo/blob/master/pkg/solidity-utils/contracts/math/LogExpMath.sol
;; MODIFIED: because we use only 128 bits instead of 256, we cannot do 20 decimal or 36 decimal accuracy like in Balancer.
;; constants
;;
;; All fixed point multiplications and divisions are inlined. This means we need to divide by ONE when multiplying
;; two numbers, and multiply by ONE when dividing them.
;; All arguments and return values are 8 decimal fixed point numbers.
(define-constant UNSIGNED_ONE_8 (pow 10 8))
;; The domain of natural exponentiation is bound by the word size and number of decimals used.
;; The largest possible result is (2^127 - 1) / 10^8,
;; which makes the largest exponent ln((2^127 - 1) / 10^8) = 69.6090111872.
;; The smallest possible result is 10^(-8), which makes largest negative argument ln(10^(-8)) = -18.420680744.
;; We use 69.0 and -18.0 to have some safety margin.
(define-constant MAX_NATURAL_EXPONENT (* 69 UNSIGNED_ONE_8))
(define-constant MIN_NATURAL_EXPONENT (* -18 UNSIGNED_ONE_8))
(define-constant MILD_EXPONENT_BOUND (/ (pow u2 u126) (to-uint UNSIGNED_ONE_8)))
;; Because largest exponent is 69, we start from 64
;; The first several a_n are too large if stored as 8 decimal numbers, and could cause intermediate overflows.
;; Instead we store them as plain integers, with 0 decimals.
(define-constant x_a_list_no_deci (list
{x_pre: 6400000000, a_pre: 62351490808116168829, use_deci: false} ;; x1 = 2^6, a1 = e^(x1)
))
;; 8 decimal constants
(define-constant x_a_list (list
{x_pre: 3200000000, a_pre: 78962960182680695161, use_deci: true} ;; x2 = 2^5, a2 = e^(x2)
{x_pre: 1600000000, a_pre: 888611052050787, use_deci: true} ;; x3 = 2^4, a3 = e^(x3)
{x_pre: 800000000, a_pre: 298095798704, use_deci: true} ;; x4 = 2^3, a4 = e^(x4)
{x_pre: 400000000, a_pre: 5459815003, use_deci: true} ;; x5 = 2^2, a5 = e^(x5)
{x_pre: 200000000, a_pre: 738905610, use_deci: true} ;; x6 = 2^1, a6 = e^(x6)
{x_pre: 100000000, a_pre: 271828183, use_deci: true} ;; x7 = 2^0, a7 = e^(x7)
{x_pre: 50000000, a_pre: 164872127, use_deci: true} ;; x8 = 2^-1, a8 = e^(x8)
{x_pre: 25000000, a_pre: 128402542, use_deci: true} ;; x9 = 2^-2, a9 = e^(x9)
{x_pre: 12500000, a_pre: 113314845, use_deci: true} ;; x10 = 2^-3, a10 = e^(x10)
{x_pre: 6250000, a_pre: 106449446, use_deci: true} ;; x11 = 2^-4, a11 = e^x(11)
))
(define-constant ERR-X-OUT-OF-BOUNDS (err u5009))
(define-constant ERR-Y-OUT-OF-BOUNDS (err u5010))
(define-constant ERR-PRODUCT-OUT-OF-BOUNDS (err u5011))
(define-constant ERR-INVALID-EXPONENT (err u5012))
(define-constant ERR-OUT-OF-BOUNDS (err u5013))
;; private functions
;;
;; Internal natural logarithm (ln(a)) with signed 8 decimal fixed point argument.
;; @desc ln-priv
;; @params a
;; @ returns (response uint)
(define-private (ln-priv (a int))
(let
(
(a_sum_no_deci (fold accumulate_division x_a_list_no_deci {a: a, sum: 0}))
(a_sum (fold accumulate_division x_a_list {a: (get a a_sum_no_deci), sum: (get sum a_sum_no_deci)}))
(out_a (get a a_sum))
(out_sum (get sum a_sum))
(z (/ (* (- out_a UNSIGNED_ONE_8) UNSIGNED_ONE_8) (+ out_a UNSIGNED_ONE_8)))
(z_squared (/ (* z z) UNSIGNED_ONE_8))
(div_list (list 3 5 7 9 11))
(num_sum_zsq (fold rolling_sum_div div_list {num: z, seriesSum: z, z_squared: z_squared}))
(seriesSum (get seriesSum num_sum_zsq))
)
(+ out_sum (* seriesSum 2))
)
)
;; @desc accumulate_division
;; @params x_a_pre ; tuple(x_pre a_pre use_deci)
;; @params rolling_a_sum ; tuple (a sum)
;; @returns uint
(define-private (accumulate_division (x_a_pre (tuple (x_pre int) (a_pre int) (use_deci bool))) (rolling_a_sum (tuple (a int) (sum int))))
(let
(
(a_pre (get a_pre x_a_pre))
(x_pre (get x_pre x_a_pre))
(use_deci (get use_deci x_a_pre))
(rolling_a (get a rolling_a_sum))
(rolling_sum (get sum rolling_a_sum))
)
(if (>= rolling_a (if use_deci a_pre (* a_pre UNSIGNED_ONE_8)))
{a: (/ (* rolling_a (if use_deci UNSIGNED_ONE_8 1)) a_pre), sum: (+ rolling_sum x_pre)}
{a: rolling_a, sum: rolling_sum}
)
)
)
;; @desc rolling_sum_div
;; @params n
;; @params rolling ; tuple (num seriesSum z_squared)
;; @Sreturns tuple
(define-private (rolling_sum_div (n int) (rolling (tuple (num int) (seriesSum int) (z_squared int))))
(let
(
(rolling_num (get num rolling))
(rolling_sum (get seriesSum rolling))
(z_squared (get z_squared rolling))
(next_num (/ (* rolling_num z_squared) UNSIGNED_ONE_8))
(next_sum (+ rolling_sum (/ next_num n)))
)
{num: next_num, seriesSum: next_sum, z_squared: z_squared}
)
)
;; Instead of computing x^y directly, we instead rely on the properties of logarithms and exponentiation to
;; arrive at that result. In particular, exp(ln(x)) = x, and ln(x^y) = y * ln(x). This means
;; x^y = exp(y * ln(x)).
;; Reverts if ln(x) * y is smaller than `MIN_NATURAL_EXPONENT`, or larger than `MAX_NATURAL_EXPONENT`.
;; @desc pow-priv
;; @params x
;; @params y
;; @returns (response uint)
(define-read-only (pow-priv (x uint) (y uint))
(let
(
(x-int (to-int x))
(y-int (to-int y))
(lnx (ln-priv x-int))
(logx-times-y (/ (* lnx y-int) UNSIGNED_ONE_8))
)
(asserts! (and (<= MIN_NATURAL_EXPONENT logx-times-y) (<= logx-times-y MAX_NATURAL_EXPONENT)) ERR-PRODUCT-OUT-OF-BOUNDS)
(ok (to-uint (try! (exp-fixed logx-times-y))))
)
)
;; @desc exp-pos
;; @params x
;; @returns (response uint)
(define-read-only (exp-pos (x int))
(begin
(asserts! (and (<= 0 x) (<= x MAX_NATURAL_EXPONENT)) ERR-INVALID-EXPONENT)
(let
(
;; For each x_n, we test if that term is present in the decomposition (if x is larger than it), and if so deduct
;; it and compute the accumulated product.
(x_product_no_deci (fold accumulate_product x_a_list_no_deci {x: x, product: 1}))
(x_adj (get x x_product_no_deci))
(firstAN (get product x_product_no_deci))
(x_product (fold accumulate_product x_a_list {x: x_adj, product: UNSIGNED_ONE_8}))
(product_out (get product x_product))
(x_out (get x x_product))
(seriesSum (+ UNSIGNED_ONE_8 x_out))
(div_list (list 2 3 4 5 6 7 8 9 10 11 12))
(term_sum_x (fold rolling_div_sum div_list {term: x_out, seriesSum: seriesSum, x: x_out}))
(sum (get seriesSum term_sum_x))
)
(ok (* (/ (* product_out sum) UNSIGNED_ONE_8) firstAN))
)
)
)
;; @desc accumulate_product
;; @params x_a_pre ; tuple (x_pre a_pre use_deci)
;; @params rolling_x_p ; tuple (x product)
;; @returns tuple
(define-private (accumulate_product (x_a_pre (tuple (x_pre int) (a_pre int) (use_deci bool))) (rolling_x_p (tuple (x int) (product int))))
(let
(
(x_pre (get x_pre x_a_pre))
(a_pre (get a_pre x_a_pre))
(use_deci (get use_deci x_a_pre))
(rolling_x (get x rolling_x_p))
(rolling_product (get product rolling_x_p))
)
(if (>= rolling_x x_pre)
{x: (- rolling_x x_pre), product: (/ (* rolling_product a_pre) (if use_deci UNSIGNED_ONE_8 1))}
{x: rolling_x, product: rolling_product}
)
)
)
;; @desc rolling_div_sum
;; @params n
;; @params rolling ; tuple (term seriesSum x)
;; @returns tuple
(define-private (rolling_div_sum (n int) (rolling (tuple (term int) (seriesSum int) (x int))))
(let
(
(rolling_term (get term rolling))
(rolling_sum (get seriesSum rolling))
(x (get x rolling))
(next_term (/ (/ (* rolling_term x) UNSIGNED_ONE_8) n))
(next_sum (+ rolling_sum next_term))
)
{term: next_term, seriesSum: next_sum, x: x}
)
)
;; public functions
;;
;; Exponentiation (x^y) with unsigned 8 decimal fixed point base and exponent.
;; @desc pow-fixed
;; @params x
;; @params y
;; @returns (response uint)
(define-read-only (pow-fixed (x uint) (y uint))
(begin
;; The ln function takes a signed value, so we need to make sure x fits in the signed 128 bit range.
(asserts! (< x (pow u2 u127)) ERR-X-OUT-OF-BOUNDS)
;; This prevents y * ln(x) from overflowing, and at the same time guarantees y fits in the signed 128 bit range.
(asserts! (< y MILD_EXPONENT_BOUND) ERR-Y-OUT-OF-BOUNDS)
(if (is-eq y u0)
(ok (to-uint UNSIGNED_ONE_8))
(if (is-eq x u0)
(ok u0)
(pow-priv x y)
)
)
)
)
;; Natural exponentiation (e^x) with signed 8 decimal fixed point exponent.
;; Reverts if `x` is smaller than MIN_NATURAL_EXPONENT, or larger than `MAX_NATURAL_EXPONENT`.
;; @desc exp-fixed
;; @params x
;; @returns (response uint)
(define-read-only (exp-fixed (x int))
(begin
(asserts! (and (<= MIN_NATURAL_EXPONENT x) (<= x MAX_NATURAL_EXPONENT)) ERR-INVALID-EXPONENT)
(if (< x 0)
;; We only handle positive exponents: e^(-x) is computed as 1 / e^x. We can safely make x positive since it
;; fits in the signed 128 bit range (as it is larger than MIN_NATURAL_EXPONENT).
;; Fixed point division requires multiplying by UNSIGNED_ONE_8.
(ok (/ (* UNSIGNED_ONE_8 UNSIGNED_ONE_8) (try! (exp-pos (* -1 x)))))
(exp-pos x)
)
)
)
;; Logarithm (log(arg, base), with signed 8 decimal fixed point base and argument.
;; @desc log-fixed
;; @params arg
;; @params base
;; @returns (response uint)
(define-read-only (log-fixed (arg int) (base int))
;; This performs a simple base change: log(arg, base) = ln(arg) / ln(base).
(let
(
(logBase (* (ln-priv base) UNSIGNED_ONE_8))
(logArg (* (ln-priv arg) UNSIGNED_ONE_8))
)
(ok (/ (* logArg UNSIGNED_ONE_8) logBase))
)
)
;; Natural logarithm (ln(a)) with signed 8 decimal fixed point argument.
;; @desc ln-fixed
;; @params a
;; @returns (response uint)
(define-read-only (ln-fixed (a int))
(begin
(asserts! (> a 0) ERR-OUT-OF-BOUNDS)
(if (< a UNSIGNED_ONE_8)
;; Since ln(a^k) = k * ln(a), we can compute ln(a) as ln(a) = ln((1/a)^(-1)) = - ln((1/a)).
;; If a is less than one, 1/a will be greater than one.
;; Fixed point division requires multiplying by UNSIGNED_ONE_8.
(ok (- 0 (ln-priv (/ (* UNSIGNED_ONE_8 UNSIGNED_ONE_8) a))))
(ok (ln-priv a))
)
)
)
;; contract initialisation
;; (set-contract-owner .executor-dao)