Fixes rounding for negative number

uzyn · Jun 24, 2020 · 03ad45c · 03ad45c
1 parent 44fd767
commit 03ad45c
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Showing 4 changed files with 39 additions and 21 deletions.
diff --git a/mod.test.ts b/mod.test.ts
@@ -219,12 +219,13 @@ Deno.test("valueOf()", () => {
 
 Deno.test("toFixed()", () => {
   assertEquals(new BigDenary("12345678.1468").toFixed(), "12345678.1468");
-  assertEquals(new BigDenary("12345678.1468").toFixed(2), "12345678.14");
+  assertEquals(new BigDenary("12345678.1468").toFixed(2), "12345678.15");
   assertEquals(new BigDenary("12345678.1468").toFixed(5), "12345678.14680");
   assertEquals(new BigDenary("12").toFixed(5), "12.00000");
   assertEquals(new BigDenary("0.1234").toFixed(5), "0.12340");
   assertEquals(new BigDenary("-0.1234").toFixed(2), "-0.12");
   assertEquals(new BigDenary("-0.1234").toFixed(5), "-0.12340");
+  assertEquals(new BigDenary("-0.1234898").toFixed(5), "-0.12349");
 });
 
 Deno.test("trimTrailingZeros()", () => {

diff --git a/mod.ts b/mod.ts
@@ -1,4 +1,9 @@
-import { countTrailingZeros, extractExp, getDecimals } from "./util.ts";
+import {
+  bigIntAbs,
+  countTrailingZeros,
+  extractExp,
+  getDecimals,
+} from "./util.ts";
 
 export interface BigDenaryRaw {
   base: bigint;
@@ -92,23 +97,12 @@ export class BigDenary {
   }
 
   toFixed(digits?: number): string {
-    const str = this.toString();
-    if (!digits || digits < 0) {
-      return str;
+    if (!digits) {
+      return this.toString();
     }
-
-    const decimals = getDecimals(str);
-
-    if (digits === decimals) {
-      return str;
-    } else if (digits > decimals) {
-      const addZeros = _strOfZeros(digits - decimals);
-      if (this._decimals === 0) {
-        return `${str}.${addZeros}`;
-      }
-      return `${str}${addZeros}`;
-    }
-    return str.substr(0, str.length - (decimals - digits));
+    const temp = new BigDenary(this);
+    temp.scaleDecimalsTo(digits);
+    return temp.toString();
   }
 
   get decimals(): number {
@@ -127,8 +121,12 @@ export class BigDenary {
       const multiplier = BigDenary.getDecimalMultiplier(adjust);
       const remainder = this.base % multiplier;
       this.base = this.base / multiplier;
-      if (remainder * 2n >= multiplier) {
-        this.base += 1n;
+      if (bigIntAbs(remainder * 2n) >= multiplier) {
+        if (this.base >= 0) {
+          this.base += 1n;
+        } else {
+          this.base -= 1n;
+        }
       }
     }
     this._decimals = _decimals;

diff --git a/util.test.ts b/util.test.ts
@@ -2,7 +2,12 @@ import {
   assertEquals,
   assertThrows,
 } from "https://deno.land/std/testing/asserts.ts";
-import { countTrailingZeros, extractExp, getDecimals } from "./util.ts";
+import {
+  bigIntAbs,
+  countTrailingZeros,
+  extractExp,
+  getDecimals,
+} from "./util.ts";
 
 Deno.test("getDecimals() with string input", () => {
   assertEquals(getDecimals("0.52135"), 5);
@@ -41,3 +46,10 @@ Deno.test("countTrailingZeros()", () => {
   assertEquals(countTrailingZeros(-9846515000000000000000n, 100), 15);
   assertEquals(countTrailingZeros(-9846515000000000000000n, 10), 10);
 });
+
+Deno.test("bigIntAbs()", () => {
+  assertEquals(bigIntAbs(0n), 0n);
+  assertEquals(bigIntAbs(-0n), 0n);
+  assertEquals(bigIntAbs(698465465n), 698465465n);
+  assertEquals(bigIntAbs(-98498465n), 98498465n);
+});
diff --git a/util.ts b/util.ts
@@ -1,3 +1,10 @@
+export function bigIntAbs(n: bigint): bigint {
+  if (n >= 0n) {
+    return n;
+  }
+  return n * -1n;
+}
+
 export function getDecimals(n: number | string): number {
   if (isNaN(n as any)) {
     throw new Error("InvalidNumber");