[Sync Iteration] javascript/coordinate-transformation/1

solutions/javascript/coordinate-transformation/1/coordinate-transformation.js

@@ -0,0 +1,79 @@
+// @ts-check
+//
+// The line above enables type checking for this file. Various IDEs interpret
+// the @ts-check directive. It will give you helpful autocompletion when
+// implementing this exercise.
+
+/**
+ * Create a function that returns a function making use of a closure to
+ * perform a repeatable 2d translation of a coordinate pair.
+ *
+ * @param {number} dx the translate x component
+ * @param {number} dy the translate y component
+ *
+ * @returns {function} a function which takes an x, y parameter, returns the
+ *  translated coordinate pair in the form [x, y]
+ */
+export function translate2d(dx, dy) {
+  return function coordinates(x, y) {
+   return [dx + x, dy + y]; 
+  }
+}
+
+/**
+ * Create a function that returns a function making use of a closure to
+ * perform a repeatable 2d scale of a coordinate pair.
+ *
+ * @param {number} sx the amount to scale the x component
+ * @param {number} sy the amount to scale the y component
+ *
+ * @returns {function} a function which takes an x, y parameter, returns the
+ *  scaled coordinate pair in the form [x, y]
+ */
+export function scale2d(sx, sy) {
+  return function coordinates(x, y) {
+    return [sx * x, sy * y]
+  };
+}
+
+/**
+ * Create a composition function that returns a function that combines two
+ * functions to perform a repeatable transformation
+ *
+ * @param {function} f the first function to apply
+ * @param {function} g the second function to apply
+ *
+ * @returns {function} a function which takes an x, y parameter, returns the
+ *  transformed coordinate pair in the form [x, y]
+ */
+export function composeTransform(f, g) {
+  return function (x, y) {
+    const [x1, y1] = f(x, y)
+    return g(x1, y1)    
+  }  
+}
+
+/**
+ * Return a function that memoizes the last result.  If the arguments are the same as the last call,
+ * then memoized result returned.
+ *
+ * @param {function} f the transformation function to memoize, assumes takes two arguments 'x' and 'y'
+ *
+ * @returns {function} a function which takes x and y arguments, and will either return the saved result
+ *  if the arguments are the same on subsequent calls, or compute a new result if they are different.
+ */
+export function memoizeTransform(f) {
+  let lastX
+  let lastY
+  let lastResult
+
+  return function (x, y) {
+    if (x === lastX && y === lastY) {
+      return lastResult
+   }
+   lastX = x
+   lastY = y
+   lastResult = f(x, y)
+   return lastResult
+  }
+}