CMPT-111 demo

examples.cpp

//Just run this code in eclipse or whatever you have set up

/* MOST IMPORTANT THINGS I HAVE TO SAY:
 * 1: Be careful! There are a lot of SMALL mistakes that can be hard to catch
 * eg. every { has a }
 * this may cause the program not even to compile and run 
 * -Every statement has a ; at the end
 *
 * Mistakes like forgetting a ;
 * have caused me to spend hours trying to figure out why seemingly perfect code wasn't working
 * and then when you realize you've forgotten a semicolon and the code works perfectly
 * it's  a (╯°□°)╯︵ ┻━┻ moment
 *
 * Anyways. Be careful! Keep an eye out for this kind of mistake.
 *
 * Another mistake I've seen once or twice with other 111 students in the last week has an easy fix,
 * -cout uses <<
 * -cin uses >>    and they are NOT interchangeable!!!!
 *
 *****************************************************
 * 2: Order of operations
 * When you manipulate numbers, like two integers x, y,
 * THERE ARE ORDER OF OPERATIONS!
 * x + y / 2 is equal to x + (y/2),
 * NOT equal to  (x + y) / 2 
 *
 *This is because *, /, % are calculated before +, -
 ****************************************************
 * 3: Getting user input.
 * Whenever you need the user to enter something, you NEED a place to store what they will enter.
 * So for example, before you use 
 * cin >> someInteger;
 * to get an integer from a user,
 * you need to have declared a variable of type int called someInteger.
 * int someInteger;
 * cin >>someInteger;
 * so in your code,  can be broken into
 *   //Variable declarations BEFORE input
 *   int x, y, z;
 *   string a;
 *   string b;
 *   ...ETC
 *   //User input
 *   cin >>x;
 *   cin >>y >> z; 
 *   ...
 *   //More code using the variable 
 *
 *****************************************************
 *3: BREAKING DOWN PROBLEMS! 
 * Read the question carefully. If the question involves getting information from the user, 
 * doing something with that information,
 * Generally the code  miiiiiight  look something like this: 
 * //1. Declare variables you need.
 * int someNumber;
 * string someString;
 * //now that you have variables, you can read user input into them!
 * 
 * cout <<"Please enter a number and a word, seperated by spaces." <<endl;
 * 
 * cin >>someNumber >>someString;
 *
 * 4. Do what you need to do with the variables.
 * //more code
 */
 
 
#include <iostream>
using namespace std;
int main() {
  //In this program, there will be 
  /*Examples of input and output*/
  
  cout <<"Hello, how are you?"<< endl;
  //is the same as:
  cout <<"Hello, " <<"how " << "are " << "you?" <<endl;
  
  string greeting = "Hello, ";
  // is the same as: 
  cout <<greeting <<"how are you?" <<endl;


  
  /*An important thing to note: 
   * You can mix together "Things you write" and data from variables you already have when you output to the screen.
   * This next example will demonstrate that.
   */ 
   
  //Two Sample problems   
  

  //Problem 1:  Ask a user for their first name, last name, and age, and then output the user's information with 
  //the data entered.
  
  cout <<endl <<endl <<endl <<"Problem 1:" <<endl;

  
  //My approach to the problem:
  
  //1. What do I need? Declare the variables for the data you need to use: first name, last name, and age 
  string firstName;
  string lastName;
  int age;
  //2. Get the data from the user:

  //Use cout to display to the user what you want,
  //and then use cin to get the user input and store it in variabels you declared.
  
  cout <<"Please enter your first name: " <<endl;
  cin >>firstName;
  cout <<"Please enter your last name: " <<endl;
  cin >>lastName;
  cout <<"Please enter your age (in years, no decimals): " <<endl;
  cin >>age;
  
  //3. Output the sentence
  cout <<"Thanks! Here is your information:" <<endl <<endl;
  
  //First: 
  //What do I want to tell the user?
  
  //If I want to write:
  //"Your name is ___ ___, and you are __ years old"
  //the ___ is where variables I already have will go. Break it down into multiple <<___'s
  cout <<"Your name is " <<firstName <<" " <<lastName <<", and you are " <<age <<" years old." <<endl;
  //Double check that each thing you write has a opening and closing ", and that there's a semicolon at the end
  //those are easy mistakes that can be harder to catch at first!
  
  //If I want to write:
  //Name: ___ ___
  //Age: __
  
  //It would look like:
  cout <<"Name: " <<firstName <<" " <<lastName <<endl  //Note the space between the names, and a new line (endl)
       <<"Age: "  <<age <<endl;

  //For the above, I only used cout once - so there is only one semicolon. I could have done:
  //cout <<"Name: " <<firstName <<" " <<lastName <<endl;
  //cout <<"Age: " <<age <<endl; //The semicolon is the end of the cout
  //So you can use one cout and multiple lines, or multiple cout's, just make sure that there's one and only ONE ; for each cout you use.
  
  
  cout <<"End of problem 1...\n Problem 2: \n";
  
  //Problem 2: Declare integer variables x0, x1, x2, x3
  //and get the input from a user,
  //and then output the following equation:
  // ((x0 + x1)/2 + x2/5 + x3*4) % 5
  
  //So this is a mess. Step one:
  //DECLARE THE VARIABLES! you need a place to store the user input.
  int x0, x1, x2, x3;
  // you could also do
  //  int x0;
  //  int x1;
  //  int x2;
  //  int x3;
  
  //Next, get the input!
  
  cout <<"Please enter four integers (numbers without decimals) seperated by spaces: " <<endl; 
  cin >>x0 >>x1 >>x2 >>x3;
  //now that we have the data, let's break down the equation
  // The order of operations is important. saying:
  // x0 + x1 / 2
  // would be the same as
  // x0 + (x1/2) 
  //This is because of the order of operations:
  // *, /, % happen before +,-
  
  //I could write: 
  //cout <<"((x0 + x1)/2 + x2/5 + x3*4) % 5 is: " <<endl;
  //but instead, I'll write the same thing, but use the numbers the user entered.

  cout <<"((" <<x0 <<" + " <<x1 <<")/2 + "<<x2 <<"/5 + "<<x3 <<"*4) % 5 is: " <<endl;
  cout << ( ((x0 + x1)/2) + (x2/5) + (x3*4) ) % 5;
  
  //If I wanted, rather than doing the calculations inside of the cout statement,
  //I could first declare a variable equal to the result of the calculation
  //int result = ( ((x0 + x1)/2) + (x2/5) + (x3*4) ) % 5;
  //and then display it:
  //cout << result <<endl;
  //and it would be the same.
  
  return 0;
}