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extend Algebrick::Matching # => main
# Simple data structures like trees
Tree = Algebrick.type do |tree|
variants Tip = type,
Node = type { fields value: Object, left: tree, right: tree }
end # => Tree(Tip | Node)
module Tree
def depth
match self,
Tip.to_m >> 0,
Node.(any, ~any, ~any) >-> left, right do
1 + [left.depth, right.depth].max
end
end
end
tree = Node[2,
Tip,
Node[5,
Node[4, Tip, Tip],
Node[6, Tip, Tip]]]
# => Node[value: 2, left: Tip, right: Node[value: 5, left: Node[value: 4, left: Tip, right: Tip], right: Node[value: 6, left: Tip, right: Tip]]]
tree.depth # => 3
# Whenever you find yourself to pass around too many fragile Hash-Array structures
# e.g. for menus.
Menu = Algebrick.type do |menu|
Item = Algebrick.type do
variants Delimiter = atom,
Link = type { fields! label: String, url: String },
Group = type { fields! label: String, submenu: menu }
end
fields! item: Item, next: menu
variants None = atom, menu
end # => Menu(None | Menu(item: Item, next: Menu))
None # => None
Item # => Item(Delimiter | Link | Group)
module Link
def self.new(*fields)
super(*fields).tap { |menu| valid! menu.url }
end
def self.valid!(url)
# stub
end
end
module Item
def draw_menu(indent = 0)
match self,
Delimiter >-> { [' '*indent + '-'*10] },
Link.(label: ~any) >-> label { [' '*indent + label] },
(on ~Group do |(label, sub_menu)|
[' '*indent + label] + sub_menu.draw_menu(indent + 2)
end)
end
end
module Menu
def self.build(*items)
items.reverse_each.reduce(None) { |menu, item| Menu[item, menu] }
end
include Enumerable
def each(&block)
it = self
loop do
break if None === it
block.call it.item
it = it.next
end
end
def draw_menu(indent = 0)
map { |item| item.draw_menu indent }.reduce(&:+)
end
end
sub_menu = Menu.build Link['Red Hat', '#red-hat'],
Delimiter,
Link['Ubuntu', '#ubuntu'],
Link['Mint', '#mint']
# => Menu[item: Link[label: Red Hat, url: #red-hat], next: Menu[item: Delimiter, next: Menu[item: Link[label: Ubuntu, url: #ubuntu], next: Menu[item: Link[label: Mint, url: #mint], next: None]]]]
menu = Menu.build Link['Home', '#home'],
Delimiter,
Group['Linux', sub_menu],
Link['About', '#about']
# => Menu[item: Link[label: Home, url: #home], next: Menu[item: Delimiter, next: Menu[item: Group[label: Linux, submenu: Menu[item: Link[label: Red Hat, url: #red-hat], next: Menu[item: Delimiter, next: Menu[item: Link[label: Ubuntu, url: #ubuntu], next: Menu[item: Link[label: Mint, url: #mint], next: None]]]]], next: Menu[item: Link[label: About, url: #about], next: None]]]]
menu.draw_menu.join("\n")
# => "Home\n----------\nLinux\n Red Hat\n ----------\n Ubuntu\n Mint\nAbout"
# Group['Products',
# Menu[]],
# Link['About', '#about']
#]]
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