[SOLVED] CS ocaml # Discussion 3: Introduction to OCaml

# Discussion 3: Introduction to OCaml

## Introduction

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

To test locally, run `dune runtest -f`.There is no submission for this assignment, it is just extra practice.

## 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 less than `n`.
**Examples**:
`ocaml
filter 3 [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]
`