Note: This repo contains the lecture notes and code examples for a lecture I prepared for Lighthouse Labs (W1D2).
-
What are some examples of web apps you use in your day-to-day life?
-
What makes [example app] useful?
-
What concerns do you have about using [example app], or if you don't use it, why not?
-
What is [example app] made of? What is required to make [example app] useful?
-
Given our answers to questions 2-4, how might we define 'web app'?
-
Given our answer to question 5, how might we define 'web development'?
This BBC Ideas video is a short introduction to where the concept of the algorithm originates, and how it became applied to computer science.
- The word algorithm is a latinized version of 8th century scholar Muhammad Ibn Musa al-Khwarizmi's name. Al-Kwharizmi made important contributions to mathematics, astronomy, geography and cartography. 'Algorithm' initially referred to the foundations of the modern numerical system, but over time came to mean a series of steps to solving a problem. Mathematician Alan Turing, one of the first computer scientists, applied the concept to machines.
Here's a more formal definition by Anany Levitin:
An algorithm is a sequence of unambiguous instructions for solving a problem, i.e., for obtaining a required output for any legitimate input in a finite amount of time.
Unambiguous: There should be no doubts about what each instruction means. This often requires that we break down all actions into very small and concrete steps.
Problem/required output: What, specifically, concretely, are we trying to accomplish? What problems are we trying to solve, and how do we define such that a computer can solve it? What does correct output look like?
This is often one of the hardest parts of programming – defining what exactly we're trying to get computers to do. That is, finding ways to interpret real-world situations so that we can make useful computations related to them.
Legitimate input: What kind of data is required to reach the required output? Where does this data come from, and how is it made computable?
Finite amount of time: The algorithm has to produce the desired output before the end of the universe.
We're going to watch a short video about following recipes for making peanut butter sandwiches.
As we watch the video, think about the following:
-
What are legitimate inputs to the recipes?
-
What are legitimate outputs, that is, how do we know that the result of following the recipe is 'correct'?
-
Why did the recipes in the video produce incorrect outputs?
Write a Node program that takes in an unlimited number of command line arguments that are numbers, goes through each of them, and prints out their sum.
Write a Node program that calculates the sum of all the numbers in a hard-coded array, and prints it out.
- A hard-coded array of numbers
- A single number, which is the sum of all the numbers in the input
| Inputs | Output |
|---|---|
| 1, 2, 3, 4, 5 | 15 |
| 1, 2, 3, 4, -5 | 5 |
| 10, 5, 10 | 25 |
| 11, 0 | 11 |
-
Prepare the input:
- Define a hard-coded array of numbers.
-
Calculate running sum using a loop:
- Declare a variable for storing the sum as it's being calculated.
- Loop over each number, adding it to the running sum.
-
Print output:
- Log the final sum to the console.
Write a Node program that takes in an unlimited number of command line arguments that are numbers, goes through each of them, and prints out their sum.
-
An unlimited amount of numbers that are passed in from the command line
-
Stretch: What should happen if no numbers are given?
-
Stretch: What should happen if the arguments passed in aren't numbers?
- A single number, which is the sum of all the numbers in the input
| Inputs | Output |
|---|---|
| 1, 2, 3, 4, 5 | 15 |
| 1, 2, 3, 4, -5 | 5 |
| 10, 5, 10 | 25 |
| 11, 0 | 11 |
-
Get and prepare input:
- Get all numbers passed in as command line arguments – these will be strings.
- Convert all the numbers as strings to numbers as integers.
-
Calculate running sum using a loop
- Declare a variable for storing the sum as it's being calculated.
- Loop over each number, adding it to the running sum.
-
Print output
- Log the final sum to the console.
Keep the following tips in mind:
-
Don't start by going to your favourite search engine! Start by writing down, perhaps as a comment in your code, what exactly you are looking for.
When we first learn how to code, it takes a lot of our brain power to understand other people's code. It's easy therefore to get lost in code we find online, and to forget what we were looking for in the first place.
If we keep a record of what exactly we are looking for, we can refer to it if we get lost, confused, or stuck.
-
Phrase your search query in the form of a question, for example:
how do you get command line arguments in node js
Make sure to include "node js" in your query if we're working in Node, or "javascript" if we're working in the browser. Answers in other programming languages aren't the most useful :)
-
Stack Overflow is your friend.
Your search results will usually include links to Stack Overflow, official documentation, and blogs/tutorials. Official documentation is dense and written for more experienced programmers, so for the time being, you'll have more luck with Stack Overflow.
-
Skip to the highest rated answer, or the one with the green checkmark (marked as the approved answer).
Learning how to ask the right questions about programming is part of learning programming. This means that many questions asked by beginners might confuse us, because they're still learning how to ask the right questions. The top or approved answers are usually more clear and are therefore a better place to start on a Stack Overflow page.
-
Don't get stuck for too long – ask a mentor for help or to search with you.
You can learn a lot by watching how a more experienced developer makes sense of Stack Overflow or other resources.
For an overview of the Lighthouse Labs curriculum, see these Google slides
-
A blog post on why we should teach/learn programming by Mark Guzdial
-
Introduction to the design & analysis of algorithms by Anany Levitin