initial impl and test

multiversx · Jun 12, 2024 · f2a3463 · f2a3463
1 parent a2e4697
commit f2a3463
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Showing 4 changed files with 43 additions and 5 deletions.
diff --git a/contracts/feature-tests/big-float-features/tests/big_float_scenario_rs_test.rs b/contracts/feature-tests/big-float-features/tests/big_float_scenario_rs_test.rs
@@ -56,6 +56,19 @@ fn big_float_overflow_test_rs() {
     assert_eq!(forth, &BigUint::from(2184473079534488064u64));
 }
 
+#[test]
+fn big_float_ln_test_rs() {
+    let fixed = BigFloat::<StaticApi>::from_frac(23i64, 2i64);
+
+    let ln_fixed = fixed.ln(BigUint::from(10u64)); // precision of 10 decimal points
+
+    println!("{ln_fixed:?}");
+    assert_eq!(
+        ln_fixed,
+        BigFloat::from_frac(31355146488i64, 10_000_000_000i64)
+    );
+}
+
 #[test]
 fn big_float_new_from_big_int_rs() {
     world().run("scenarios/big_float_new_from_big_int.scen.json");

diff --git a/framework/base/src/types/managed/basic/big_float.rs b/framework/base/src/types/managed/basic/big_float.rs
@@ -168,8 +168,33 @@ impl<M: ManagedTypeApi> BigFloat<M> {
         (self * denominator).trunc()
     }
 
-    pub fn to_managed_decimal<T: Decimals>(self, decimals: T) -> ManagedDecimal<M, T> {
-        ManagedDecimal::<M, T>::from_big_float(self, decimals)
+    pub fn to_managed_decimal<T: Decimals>(&self, decimals: T) -> ManagedDecimal<M, T> {
+        ManagedDecimal::<M, T>::from_big_float(&self, decimals)
+    }
+
+    pub fn ln(&self, precision: BigUint<M>) -> Self {
+        // find the highest power of 2 less than or equal to self
+        let mng_dec = self
+            .to_fixed_point(&BigFloat::from(precision))
+            .into_big_uint()
+            .unwrap_or_sc_panic("can't calculate ln for this number");
+
+        let log2 = mng_dec.log2(); // most significant bit
+        let divisor = BigFloat::from(1 << log2);
+        let x = self / &divisor; // normalize to [1.0, 2.0]
+
+        let ln_of_2 = BigFloat::from_frac(69314718i64, 100_000_000i64); // 0.69314718 8 decimals
+        let first = BigFloat::from_frac(17417939i64, 10_000_000i64); // 1.7417939, 7 decimals
+        let second = BigFloat::from_frac(28212026i64, 10_000_000i64); // 2.8212026, 7 decimals
+        let third = BigFloat::from_frac(14699568i64, 10_000_000i64); // 1.4699568, 7 decimals
+        let fourth = BigFloat::from_frac(44717955i64, 100_000_000i64); // 0.44717955, 8 decimals
+        let fifth = BigFloat::from_frac(56570851i64, 1_000_000_000i64); // 0.056570851, 9 decimals
+
+        // approximating polynom to get the result
+        let result =
+            (((fourth - fifth * x.clone()) * x.clone() - third) * x.clone() + second) * x - first;
+        let add_member = BigFloat::from_big_uint(&BigUint::from(log2)) * ln_of_2;
+        result + add_member
     }
 }
 

diff --git a/framework/base/src/types/managed/wrapped/managed_decimal.rs b/framework/base/src/types/managed/wrapped/managed_decimal.rs
@@ -126,7 +126,7 @@ impl<M: ManagedTypeApi, D: Decimals> ManagedDecimal<M, D> {
     }
 
     pub fn from_big_float<T: Decimals>(
-        big_float: BigFloat<M>,
+        big_float: &BigFloat<M>,
         num_decimals: T,
     ) -> ManagedDecimal<M, T> {
         let scaling_factor: &BigUint<M> = &num_decimals.scaling_factor();

diff --git a/framework/scenario/tests/managed_decimal_test.rs b/framework/scenario/tests/managed_decimal_test.rs
@@ -64,10 +64,10 @@ pub fn test_managed_decimal() {
 
     let float_1 = BigFloat::<StaticApi>::from_frac(3i64, 2i64);
     let fixed_float_1 = ManagedDecimal::<StaticApi, ConstDecimals<1>>::from_big_float(
-        float_1.clone(),
+        &float_1,
         ConstDecimals::<1>,
     );
-    let fixed_float_2 = ManagedDecimal::<StaticApi, NumDecimals>::from_big_float(float_1, 1usize);
+    let fixed_float_2 = ManagedDecimal::<StaticApi, NumDecimals>::from_big_float(&float_1, 1usize);
 
     assert_eq!(
         fixed_float_1,