fix Decimal code

Author: dynst

packages/math/src/decimal.ts

@@ -127,7 +127,7 @@ export class Decimal {
 
   /** Returns the greatest decimal <= this which has no fractional part (rounding down) */
   public floor(): Decimal {
-    const factor = 10n ** BigNum(this.data.fractionalDigits);
+    const factor = 10n ** BigInt(this.data.fractionalDigits);
     const whole = this.data.atomics / factor;
     const fractional = this.data.atomics % factor;
 
@@ -195,7 +195,7 @@ export class Decimal {
   public minus(b: Decimal): Decimal {
     if (this.fractionalDigits !== b.fractionalDigits) throw new Error("Fractional digits do not match");
     const difference = this.data.atomics - b.data.atomics;
-    if (difference.ltn(0)) throw new Error("Difference must not be negative");
+    if (difference < 0n) throw new Error("Difference must not be negative");
     return new Decimal(difference.toString(), this.fractionalDigits);
   }
 
@@ -205,7 +205,7 @@ export class Decimal {
    * We only allow multiplication by unsigned integers to avoid rounding errors.
    */
   public multiply(b: Uint32 | Uint53 | Uint64): Decimal {
-    const product = this.data.atomics * b.toBigInt());
+    const product = this.data.atomics * b.toBigInt();
     return new Decimal(product.toString(), this.fractionalDigits);
   }