refactor(utils): Extract trampoline and identity utility functions

Author: sargalias

src/recursion-practice/power/power.js

@@ -1,3 +1,5 @@
+import { trampoline, identity } from '../utils';
+
 // Power
 const power = (base, exponent) => {
   if (exponent === 0) {
@@ -16,7 +18,6 @@ const powerPTC = (base, exponent, resultSoFar = 1) => {
 };
 
 // Power continuous passing style
-const identity = x => x;
 const powerCPS = (base, exponent, cont = identity) => {
   if (exponent === 0) {
     return cont(1);
@@ -25,16 +26,6 @@ const powerCPS = (base, exponent, cont = identity) => {
 };
 
 // Power with trampolining
-const trampoline = fn => (...args) => {
-  let result = fn(...args);
-
-  while (typeof result === 'function') {
-    result = result();
-  }
-
-  return result;
-};
-
 const powerTrampoline = trampoline(function _power(
   base,
   exponent,

src/recursion-practice/sumRange/sumRange.js

@@ -1,3 +1,5 @@
+import { trampoline, identity } from '../utils';
+
 // sumRange with no optimisations
 const sumRange = n => {
   if (n <= 1) return n;
@@ -29,7 +31,6 @@ const sumRangePTCFacade = (() => {
 })();
 
 // sumRange with continuous passing style
-const identity = x => x;
 const sumRangeCPS = (n, cont = identity) => {
   if (n <= 1) return cont(n);
 
@@ -38,14 +39,6 @@ const sumRangeCPS = (n, cont = identity) => {
 };
 
 // sumRange with trampolining
-const trampoline = fn => (...args) => {
-  let result = fn(...args);
-  while (typeof result === 'function') {
-    result = result();
-  }
-  return result;
-};
-
 const sumRangeTrampoline = trampoline(function _sumRange(n, totalSoFar = 0) {
   const newTotalSoFar = n + totalSoFar;
 

src/recursion-practice/utils/index.js

@@ -0,0 +1 @@
+export * from './utils';

src/recursion-practice/utils/utils.js

@@ -0,0 +1,13 @@
+const trampoline = fn => (...args) => {
+  let result = fn(...args);
+
+  while (typeof result === 'function') {
+    result = result();
+  }
+
+  return result;
+};
+
+const identity = x => x;
+
+export { trampoline, identity };