OCAML-Discussion 3 Introduction to OCaml Solved

This exercise consists of a few short functions to help you familiarize yourself with OCaml.  You can review the content of the discussion in [notes.rb](notes.rb), which includes the topics and examples from the discussion video.  Also, check out [utop-tutorial.md](utop-tutorial.md) for an introduction to using `utop`.

 

### Testing & Submitting

 

You will submit this project to [Gradescope](https://www.gradescope.com/courses/171498/assignments/681774).  You may only submit the **disc3.rb** file.  To test locally, run `dune runtest -f`.

 

## Part 1: Type inference

 

At the top of [disc3.ml](src/disc3.ml), there are a few function definitions. Try determining the types of these functions and check your answers with `utop`.  This portion of the discussion is not tested (and thus not graded), but these kinds of exercises may appear on quizzes and exams!

 

## Part 2: Type definitions

 

You will have to fill in definitions for the functions `tf1`, `tf2`, `tf3` such that they have the type that is expected in the `.mli`. The operation of the function does not matter, as long as they have the correct types.

 

#### `tf1 a`

 

- **Type**: `string - int`

 

#### `tf2 a b c`

 

- **Type**: `'a - 'b - 'b - bool`

 

#### `tf3 a b`

 

- **Type**: `'a list - 'a list - 'a`

- **Note**: For this one, you can assume that the lists `a` and `b` are not empty.

 

## Part 3: Functions

 

#### `concat str1 str2`

 

- **Type**: `string - string - string`

- **Description**: Appends `str2` to the end of `str1`.

- **Examples**:

  ```ocaml

  concat "" "" = ""

  concat "" "abc" = "abc"

  concat "xyz" "" = "xyz"

  concat "abc" "xyz" = "abcxyz"

  ```

 

#### `add_to_float integer flt`

 

- **Type**: `int - float - float`

- **Description**: Adds `integer` and `flt` and returns a float representation of the sum.

- **Examples**:

  ```ocaml

  add_to_float 3 4.8 = 7.8

  add_to_float 0 0.0 = 0.0

  ```

 

#### `fib n`

 

- **Type**: `int - int`

- **Description**: Calculates the nth [Fibonacci number](https://en.wikipedia.org/wiki/Fibonacci_number).

- **Examples**:

  ```ocaml

  fib 0 = 0

  fib 1 = 1

  fib 2 = 1

  fib 3 = 2

  fib 6 = 8

  ```

 

## Part 4: Lists

 

#### `add_three lst`

 

- **Type**: `int list - int list`

- **Description**: Adds 3 to each element in `lst`.

- **Examples**:

  ```ocaml

  add_three [] = []

  add_three [1] = [4]

  add_three [1; 3; 5] = [4; 6; 8]

  ```

 

#### `filter n lst`

 

- **Type**: `int - int list - int list`

- **Description**: Given an integer `n` and a list `lst`, Remove elements from `lst` that are greater than `n`.

- **Examples**:

  ```ocaml

  filter 2 [1; 2; 3; 3; 2; 1] = [1; 2; 2; 1]

  filter 5 [-1; 2; 3; 4] = [-1; 2; 3; 4]

  ```

 

#### `double lst`

 

- **Type**: `'a list - 'a list`

- **Description**: Given a list `lst`, return a new list that has two copies of every element in `lst`.

- **Examples**: 

  ```ocaml

  double [1;2;3;4] = [1;1;2;2;3;3;4;4]

  double ["a"; "b"; "c"] = ["a"; "a"; "b"; "b"; "c"; "c"]

  ```