add – Addition – Computer Science by Example

add – Addition

If I have two oranges and three tomatoes, how many items to I have?

Write a program that reads several pairs of numbers and, for each pair, prints the sum. The standard input and output devices are usually the keyboard and screen of a command line session. Here is an example session with this program:

Input and Output

Each line of input contains two numbers x and y where -2 000 000 000 ≤ x, y ≤ 2 000 000 000

For each line of input there should be a line of output with the result of adding x to y.

Numbers may be given in the input with leading zeroes. The output should have no leading zeroes. Input is terminated by the end-of-file (EOF)

Example input

Example output

The `add` function

In order to get a full score, your program should be implemented using an add function that receives two integers as arguments and returns an integer. Please refer to the information for the chosen language:

C prototype: int add(int x, int y);
Python definition: def add(x,y):
Haskell type: add :: Int -> Int -> Int
C++ prototype: int add(int x, int y);
C# definition: public static int Add(int x, int y) inside a class Program
Java definition: public static int add(int x, int y) inside a public class Add
JavaScript definition: function add(x, y)
Lua definition: function add(x, y)
Ruby definition: def add(x,y)
Racket definition: (define (add x y) ...)
Scheme definition: (define (add x y) ...)

The add function should not print anything. It should just perform the computation and return an integer. The function and input/output processing must exist in the same program. Create a single submission with the function and main program. If you are confused by the above, try earning a partial score first.

Specifically for this exercise when using Python, JavaScript, Lua or Ruby, avoid using sys.exit(), process.exit(), os.exit() or exit, as your program is appended with some extra assertions in one of the test sets.

Scoring

Submit your solution to be graded according to the following list:

1/6: works for the above example but produces output in an incorrect format
2/6: works for the above example and produces output in the correct format
3/6: works for 100 sums
4/6: works for 10 000 sums
5/6: works for edge cases
6/6: implements the add function

Hints

If you do not know where to start, read the Computer Science by Example book. First, setup your environment then learn the programming basics. Here are some hints:

Automated judge: Keep in mind that when your program is submitted it will not be run by a human but instead by an automated judge. Instructions should be followed exactly or the judge will not give you a full score.

Your program should not print messages like Please type two numbers: or The sum is:. Instead, just print the result followed by a line break as in the example output.
Produce output as you go: You do not need to accumulate input and then produce everything at the end. It is enough to produce output as you go. As soon as you read a pair of numbers write their sum to standard output.
Detecting the end of file. In this exercise, input is terminated by the end-of-file (EOF). Here are ways to detect EOF in C, Python and Haskell:
- In C. The scanf function returns the numbers of items read from stdin. Since this exercise requires you to read two numbers each line, you can compare scanf’s result to one as a while condition:
```
  while (scanf(...)==2) {
      ...
  }
```
  Which translates to, “while you’re able to read two items from standard input, do …”
- In Python. The pattern for line in sys.stdin: can be used to create a loop where a file is processed line by line until the end-of-file (EOF).
- In Haskell. You can use interact to declare the main function and implement your solution as a function from String to String:
```
  io :: String -> String
  io = ...

  main :: IO
  main = interact io
```
  EOF is then represented as the nil list constructor ("" or []) at the end of the argument String.
On the terminal, you can simulate the end-of-file (EOF) by holding “Ctrl” and pressing “D”, i.e., Ctrl-D.
Beware of leading zeroes. C users should beware of leading zeroes. Use %d instead of %i to avoid treating numbers with leading zeroes as octals.

try first: repeat add1

try next: mult

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