BYU CS classes

Learn the basics of the Julia Language.

For this lab, you should use at least Julia v.0.4. You may use the binary hosted in Dr. Wingate's home directory, at

/users/faculty/wingated/cs330/languages/julia-2e358ce975/bin

or you may install Julia yourself.

For this lab, you will need to implement the following functions and data structures in Julia:

• area
• in_shape
• greyscale
• invert
• count_person
• average_age
• tree_map
• add_last_name
• eye_colors

Define the following data structures.

abstract Shape
 
type Position
  x::Real
  y::Real
end
 
type Circ <: Shape
  center::Position
  radius::Real
end
 
type Square <: Shape
  upper_left::Position
  length::Real
end
 
type Rect <: Shape
  upper_left::Position
  width::Real
  height::Real
end

function area(shape) ...

Returns the area of the given shape. where Shape is some concrete instance of the abstract shape type class. For this a few of the following instead of testing for class member ship it is easier to write three different functions, one for each concrete instance of shape. ie: function area(shape::rect)…

function in_shape(shape::Shape, position::Position) ...

Returns if the position is inside the shape. Assume standard math coordinates where y is positive going up. The bounds are inclusive.

Define the Following type in your code

type Pixel
  r::Real
  g::Real
  b::Real
end

function greyscale(picture::Array{Pixel,2}) ...

Takes a 2d array of pixels and greys out each pixel. This is done by averaging together the r g b values and then setting r g b to the average.

Hint: Julias map works over multi-dimensional arrays

function invert(picture::Array{Pixel,2}) ...

Takes a 2d array and pixels and inverts each one. Inverting is done by setting r to `255 - r` and the other two in the same manner.

Define the following types in your code

abstract TreeItem
 
type Person <: TreeItem
  name::AbstractString
  birthyear::Integer
  eyecolor::Symbol
  father::TreeItem
  mother::TreeItem
end
 
type Unknown <: TreeItem
end

function count_persons(tree)

Counts the number of people in the tree. Unknowns do not count as people.

function average_age(tree)

Calculates the average age of the people in the tree. Use this years date 2017. Unknowns do not count as people.

function tree_map(f, tree)

Takes a function f and applies it to each known member of the tree. The function f takes one parameter and returns a treeItem. Tree_map will return a *new* tree. Tree_map should leave the original tree unchanged, unless f applies a mutation.

function add_last_name(name::AbstractString, tree)

Appends name to the end of the name of each member of the tree. You should use tree_map. You do not need to add a space in front of the name.

Hint: Julia uses * for string concatenation.

function eye_colors(tree)

Returns a list of all eye colors in the tree. A color can appear more than once. For grading visit the order child, father, mother.

hint: Julia arrays can be appended using the ; for example [a;b;c] will create a list with a, b, and c in it. The empty list [] is ignored.