first and last

README.md

@@ -25,4 +25,8 @@ const result = bitset
   .toggleBE(1) // 0100 0010
   .unsign() // >>> 0
   .value
+
+const last6 = bitset
+  .last(6) // 00 0010
+  .toString() // "000010"
 ```

package.json

@@ -1,7 +1,7 @@
 {
   "type": "module",
   "name": "@hazae41/bitset",
-  "version": "1.0.0",
+  "version": "1.0.1",
   "description": "Utilities for arithmetic bitwise operations in JavaScript",
   "homepage": "https://github.com/hazae41/bitset",
   "repository": "github:hazae41/bitset",

src/mods/bitset/bitset.test.ts

@@ -70,13 +70,13 @@ test("Export Int32 to Uint32", async () => {
 test("First", async () => {
   const bitset = new Bitset(0b11100011, 8)
 
-  assert(bitset.first(2) === 3)
-  assert(bitset.first(3) === 7)
+  assert(bitset.first(2).value === 3)
+  assert(bitset.first(3).value === 7)
 })
 
 test("Last", async () => {
   const bitset = new Bitset(0b11100111, 8)
 
-  assert(bitset.last(2) === 3)
-  assert(bitset.last(3) === 7)
+  assert(bitset.last(2).value === 3)
+  assert(bitset.last(3).value === 7)
 })

src/mods/bitset/bitset.ts

@@ -8,7 +8,7 @@ export class Bitset {
   /**
    * Get the value as a left-padded binary string
    * 
-   * @returns 
+   * @returns string
    */
   toString() {
     return this.value.toString(2).padStart(this.length, "0")
@@ -17,7 +17,7 @@ export class Bitset {
   /**
    * Transform the value to an unsigned 32-bits number
    * 
-   * @returns 
+   * @returns the same Bitset
    */
   unsign() {
     this.value = this.value >>> 0
@@ -28,7 +28,7 @@ export class Bitset {
   /**
    * Bitwise NOT
    * 
-   * @returns 
+   * @returns the same Bitset
    */
   not() {
     for (let i = 0; i < this.length; i++)
@@ -40,18 +40,17 @@ export class Bitset {
    * Get the bit at big-endian index
    * 
    * @param index 
-   * @returns 
+   * @returns boolean
    */
   getBE(index: number) {
     return Boolean(this.value & (1 << (this.length - index - 1)))
   }
 
-
   /**
    * Get the bit at little-endian index
    * 
    * @param index 
-   * @returns 
+   * @returns boolean
    */
   getLE(index: number) {
     return Boolean(this.value & (1 << index))
@@ -61,7 +60,7 @@ export class Bitset {
    * Toggle the bit at big-endian index
    * 
    * @param index 
-   * @returns 
+   * @returns the same Bitset
    */
   toggleBE(index: number) {
     this.value ^= (1 << (this.length - index - 1))
@@ -73,7 +72,7 @@ export class Bitset {
    * Toggle the bit at little-endian index
    * 
    * @param index 
-   * @returns 
+   * @returns the same Bitset
    */
   toggleLE(index: number) {
     this.value ^= (1 << index)
@@ -85,7 +84,7 @@ export class Bitset {
    * Enable the bit at big-endian index
    * 
    * @param index 
-   * @returns 
+   * @returns the same Bitset
    */
   enableBE(index: number) {
     this.value |= (1 << (this.length - index - 1))
@@ -97,7 +96,7 @@ export class Bitset {
    * Enable the bit at little-endian index
    * 
    * @param index 
-   * @returns 
+   * @returns the same Bitset
    */
   enableLE(index: number) {
     this.value |= (1 << index)
@@ -109,7 +108,7 @@ export class Bitset {
    * Disable the bit at big-endian index
    * 
    * @param index 
-   * @returns 
+   * @returns the same Bitset
    */
   disableBE(index: number) {
     this.value &= ~(1 << (this.length - index - 1))
@@ -121,7 +120,7 @@ export class Bitset {
    * Disable the bit at little-endian index
    * 
    * @param index 
-   * @returns 
+   * @returns the same Bitset
    */
   disableLE(index: number) {
     this.value &= ~(1 << index)
@@ -134,7 +133,7 @@ export class Bitset {
    * 
    * @param index 
    * @param value 
-   * @returns 
+   * @returns the same Bitset
    */
   setBE(index: number, value: boolean) {
     if (value)
@@ -148,7 +147,7 @@ export class Bitset {
    * 
    * @param index 
    * @param value 
-   * @returns 
+   * @returns the same Bitset
    */
   setLE(index: number, value: boolean) {
     if (value)
@@ -161,19 +160,23 @@ export class Bitset {
    * Get first count bits
    * 
    * @param count number of bits to get
-   * @returns 
+   * @returns a new Bitset
    */
   first(count: number) {
-    return this.value >> (this.length - count)
+    const value = this.value >> (this.length - count)
+
+    return new Bitset(value, count)
   }
 
   /**
    * Get last count bits
    * 
    * @param count number of bits to get
-   * @returns 
+   * @returns a new Bitset
    */
   last(count: number) {
-    return this.value & ((1 << count) - 1)
+    const value = this.value & ((1 << count) - 1)
+
+    return new Bitset(value, count)
   }
 }