mapElements

Quick Index

Steps
Demo
Problem Statement
Hints
Solution

Take a shot at writing the program after viewing the problem statement
When desired, look at the hints
When desired, look at the solution

Here is a demo (1 min 54 seconds)

The function mapElements returns a new collection which is the passed collection mapped (converted) to new elements using the passed mapping function.

Write an algorithm (human language) and then write pseudocode.

Function header: function mapElements(elements, mapFct)

The passed mapFct is invoked with input that is an element (from the passed elements array) and outputs a new element.

Example Hand Calculation #1:

elements = [2, 3, 4];
mapFct = (x) => x * x;
mapElements(elements, mapFct) outputs [4, 9, 16]

Example Hand Calculation #2:

elements = ['Asha', 'Acheampong', 'Mo'];
mapFct = (str) => str.length;
mapElements(elements, mapFct) outputs [4, 10, 2]

Hints

General Hints:

Write algorithm in human language using wording/terms of your choice
Keep as simple as possible
Think through solutions using the example data
Take initial shot, then fine tune (improve) it
Use all parameters passed to function

Specific Hints:

You may want to start with the last line of the algorithm (the "Return" statement)
Iterate over elements

Solution

Algorithm:

/**Returns new collection using mapFct to produce new elements */
function mapElements(elements, mapFct)
	Let newElements = new dynamic (growable) array
	Iterate over collection "elements" (let "nextElement" be the iteration variable)
		Let newElement = mapFct(nextElement)
		Add newElement to newElements
	Return newElements

Pseudocode:

/**Returns new collection using mapFct to produce new elements */
function mapElements(elements, mapFct) {
	let newElements = [];
	for (let nextElem of elements) {
		let newElem = mapFct(nextElem);
		newElements.add(newElem);
	}
	return newElements
}

//-------------------------------------------
//Tests
var elements, squareFct, lengthFct, result;

elements = [2, 3, 4];
squareFct = (x) => x * x;
println("Data: " + elements);
println("Squares: " + mapElements(elements, squareFct));

elements = ['Asha', 'Acheampong', 'Mo'];
lengthFct= (str) => str.length;
println("\nData: " + elements);
println("Lengths: " + mapElements(elements, lengthFct));

Object Oriented Programming

mapElements

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