Ruby/Collections/Set
Материал из Wiki.crossplatform.ru
a-b: is the elements of a except for those also in b
require "set" primes = Set[2, 3, 5, 7] odds = Set[1, 3, 5, 7, 9] p primes-odds # => #<Set: {2}> p odds-primes # => #<Set: {1, 9}> p primes.difference(odds) # A named method alias
a^b is the set of values that appear in one set but not both: (a|b)-(a&b)
require "set" primes = Set[2, 3, 5, 7] odds = Set[1, 3, 5, 7, 9] primes ^ odds # => #<Set: {1, 2, 9}>
Add element to a set
require "set" s = Set[] # start with an empty set s << 1 # => #<Set: {1}> s.add 2 # => #<Set: {1, 2}>: add is a synonym for << s << 3 << 4 << 5 # => #<Set: {5, 1, 2, 3, 4}>: can be chained s.add 3 # => #<Set: {5, 1, 2, 3, 4}>: value unchanged s.add? 6 # => #<Set: {5, 6, 1, 2, 3, 4}> s.add? 3 # => nil: the set was not changed
Add new method to set
require "set" class OrderedSet < Set def initialize @hash ||= OrderedHash.new end end
Add set operation to Array
require "set" class Array def classify h = {} each do |i| x = yield(i) (h[x] ||= self.class.new) << i end h end def divide(&block) Set.new(classify(&block).values) end end p [1,1,2,6,6,7,101].divide { |x| x % 2 } # => #<Set: {[2, 6, 6], [1, 1, 7, 101]}>
Classify a set into three
require "set" s = ["a","b","c",1, 2, 3, -1.0, -2.0, -4.0].to_set p s.classify { |x| x.class }
Classify set elements as even or odd
require "set" s = (0..3).to_set # => #<Set: {0, 1, 2, 3}> s.classify {|x| x%2} # => {0=>#<Set: {0, 2}>, 1=>#<Set: {1, 3}>}
Clear a set
require "set" s = Set.new(1..3) # Initial set s.clear # => #<Set: {}>
Collect in place
require "set" s = Set[1, 2, 3, 4, 5] # => #<Set: {5, 1, 2, 3, 4}> s.collect! {|x| x/2 } # => #<Set: {0, 12, 2, 8, 4}>
Compare two sets
require "set" s = (1..3).to_set s == Set[3,2,1] # => true: uses eql? to compare set elements
Convert a hash to set and divide
require "set" connections = { 1 => 2, 2 => 3, 3 => 1, 4 => 1 } [1,2,3,4].to_set.divide { |x,y| connections[x] == y } # => #<Set: {#<Set: {1, 2, 3}>, #<Set: {4}>}>
Convert set to array
require "set" s = (1..3).to_set s.to_a # => [1, 2, 3]
Create set with constant values
require "set" Set["cow", "pig", "hen"] # => #<Set: {"cow", "pig", "hen"}>
Create set with Set.new
require "set" p Set.new(1..5) # => #<Set: {5, 1, 2, 3, 4}> p Set.new([1,2,3]) # => #<Set: {1, 2, 3}> p Set.new([1,2,3]) {|x| x+1} # => #<Set: {2, 3, 4}>
Delete elements from a set with block
require "set" primes = Set[2, 3, 5, 7] # set of prime numbers primes.delete_if {|x| x%2==1} # => #<Set: {2}>: remove odds primes.delete_if {|x| x%2==1} # => #<Set: {2}>: unchanged
Divide a set by absolute value
require "set" s = [1, 2, 3, -1, -2, -4].to_set # Divide the set into sets of numbers with the same absolute value. p s.divide { |x,y| x.abs == y.abs } # => #<Set: {#<Set: {-1, 1}>, # => #<Set: {2, -2}>, # => #<Set: {-4}>, # => #<Set: {3}>}>
Divide a set by even and odd value
require "set" s = Set.new((1..10).collect) # Divide the set into the "0" subset and the "1" subset: that is, the # "even" subset and the "odd" subset. p s.divide { |x| x % 2 } # => #<Set: {#<Set: {6, 2, 8, 4, 10}>, #<Set: {5, 1, 7, 3, 9}>}>
Divide a set by its element"s class
require "set" s = Set.new([1, 2, 3, "a", "b", "c", -1.0, -2.0, -3.0]) # Divide the set into the "String subset, the "Fixnum" subset, and the # "Float" subset. p s.divide { |x| x.class } # => #<Set: {#<Set: {"a", "b", "c"}>, # => #<Set: {1, 2, 3}>, # => #<Set: {-1.0, -3.0, -2.0}>}>
Divide a set by value
require "set" s = Set.new((1..10).collect) # Divide the set into the "true" subset and the "false" subset: that # is, the "less than 5" subset and the "not less than 5" subset. p s.divide { |x| x < 5 } # => #<Set: {#<Set: {5, 6, 7, 8, 9, 10}>, #<Set: {1, 2, 3, 4}>}>
Divide set
require "set" s = (0..3).to_set # => #<Set: {0, 1, 2, 3}> s.divide {|x| x%2} # => #<Set: {#<Set: {0, 2}>, #<Set: {1, 3}>}>
Divide set into three sub sets
require "set" s = [1, 2, 3, -1, -2, -4].to_set # Divide the set into sets of adjacent numbers p s.divide { |x,y| (x-y).abs == 1 } # => #<Set: {#<Set: {1, 2, 3}>, # => #<Set: {-1}>, # => #<Set: {-4, -3}>}>
Divide with block
require "set" s = %w[ant ape cow hen hog].to_set # A set of words s.divide {|x,y| x[0] == y[0]} # Divide into subsets by first letter # => #<Set:{#<Set:{"hog", "hen"}>, #<Set:{"cow"}>, #<Set:{"ape", "ant"}>}>
Do an in-place intersection like this:
require "set" s = (1..5).to_set t = (4..8).to_set s.reject! {|x| not t.include? x} # => #<Set: {5, 4}>
Each loop
require "set" s = Set[1, 2, 3, 4, 5] # => #<Set: {5, 1, 2, 3, 4}> s.each {|x| print x } # prints "51234": arbitrary order before Ruby 1.9
Flatten the subsets
require "set" s = %w[ant ape cow hen hog].to_set # A set of words t = s.divide {|x,y| x[0] == y[0]} # Divide it into subsets t.flatten! # Flatten the subsets t == s # => true
Inspect a set
require "set" s = (1..3).to_set s.inspect # => "#<Set: {1, 2, 3}>": useful
Is it a subset
require "set" s = Set[2, 3, 5] t = Set[2, 3, 5, 7] p s.subset? t # => true p t.subset? s # => false p s.proper_subset? t # => true p t.superset? s # => true p t.proper_superset? s # => true p s.subset? s # => true p s.proper_subset? s # => false
Is it empty
require "set" s = Set.new(1..3) # Initial set s.empty? # => true
Is it in a set
require "set" s = Set.new(1..3) # => #<Set: {1, 2, 3}> p s.include? 1 # => true p s.member? 0 # => false: member? is a synonym
Map elements in a set
require "set" s = Set[1, 2, 3, 4, 5] # => #<Set: {5, 1, 2, 3, 4}> s.map! {|x| x*x } # => #<Set: {16, 1, 25, 9, 4}>
merge a range to a set
require "set" s = (1..3).to_set # => #<Set: {1, 2, 3}> s.merge(2..5) # => #<Set: {5, 1, 2, 3, 4}>
Partitioning or Classifying a Set
require "set" p s = Set.new((1..10).collect) # => #<Set: {5, 6, 1, 7, 2, 8, 3, 9, 4, 10}>
Reject elements from a set
require "set" primes = Set[2, 3, 5, 7] # set of prime numbers primes.reject! {|x| x%2==1} # => nil: unchanged
Remove elements from a set
require "set" s = (1..3).to_set # => #<Set: {1, 2, 3}> s.delete 1 # => #<Set: {2, 3}> s.delete 1 # => #<Set: {2, 3}>: unchanged s.delete? 1 # => nil: returns nil when no change s.delete? 2 # => #<Set: {3}>: otherwise returns set
Replace a set
require "set" s = Set.new(1..3) # Initial set s.replace(3..4) # Replace all elements. Argument is any enumerable
Set includes and membership
require "set" primes = Set[2, 3, 5, 7] primes.include? 2 # => true primes.member? 1 # => false
Set length, size and empty?
require "set" s = Set[2, 3, 5] p s.length # => 3 p s.size # => 3: a synonym for length p s.empty? # => false p Set.new.empty? # => true
Set subtraction
require "set" s = (1..3).to_set # => #<Set: {1, 2, 3}> s.subtract(2..10) # => #<Set: {1}>
Sort with block
require "set" w = Set["apple","Beet","carrot"] # A set of words to sort w.sort # ["Beet","apple","carrot"]: alphabetical w.sort {|a,b| b<=>a } # ["carrot","apple","Beet"]: reverse w.sort {|a,b| a.casecmp(b) } # ["apple","Beet","carrot"]: ignore case w.sort {|a,b| b.size<=>a.size} # ["carrot","apple","Beet"]: reverse length
The intersection is the set of values that appear in both
require "set" primes = Set[2, 3, 5, 7] odds = Set[1, 3, 5, 7, 9] p primes & odds # => #<Set: {5, 7, 3}> p primes.intersection(odds) # this is an explicitly named alias
The union is the set of values that appear in either
require "set" primes = Set[2, 3, 5, 7] odds = Set[1, 3, 5, 7, 9] p primes | odds # => #<Set: {5, 1, 7, 2, 3, 9}> p primes.union(odds) # an explicitly named alias
