Starby Four

Global Variables–Variable References Lecture $–Use this sign to create a global variable in Ruby. Ex: def say_hello $message = “hello globe” end say_hello p $message # => “hello globe” More Methods! object_id can be used to see what memory location a particular variable points to . ex: variable.object_id => 7018903, or whatever number the computer assigned. Initializing an Array! *(Variable References Lecture) So we know that ‘arr = [ ]‘ will create a new empty array. We can use ‘arr = Array.new()‘ to initialize an array of a certain length by passing the length we want into the parameter (argument). ex: Array.new(3) #a new array with 3 elements => [nil,…

Sorting & Swapping Elements, & Bubble Sort Algorithms!!! Algorithm a sequence of actions to take! Sorting Algorithms Swapping Elements Operation: array = [“a”, “b”, “c”, “d”] #let’s swap “a” & “b” temp = array[0]; #save a copy of the first ele array[0] = array[1]; #overwrite the 1st ele with the 2nd ele array[1] = temp; #overwrite the 2nd ele with the 1st ele copy p array # => [“b”, “a”, “c”, “d”] This works but is a bit messy. Ruby has a clean shortcut (that also works in Python!)! array = [“a”, “b”, “c”, “d”] #let’s swap “a” & “b” array[0], array[1] = array[1], array[0] p array # => [“b”,…

Symbols in Ruby Symbols are an additional data type, similar to strings, but different. str = ” “ strings are wrapped in quotes. Symbol = : symbols begin with a colon. Ex: str = “hello # the string sym = :hello # the symbol p str.length # => 5 p sym.length # => 5 p str[1] # => “e” p sym[1] # => “e” p str == sym # => false #Lesson…A string is DIFFERENT from a symbol! Strings are mutable (can be changed, or mutated). Symbols are immutable (can never be changed, or mutated). Because strings are mutable, they are always stored in a new memory location (even if…

More Common Enumerable’s .all?–return ‘true’ when all elements result in true when passed into the block. Ex: p [2,4,6].all? { |el| el.even? } # =>(returns) true Ex: p [2,3,6].all? { |el| el.even? } # => false .any?–return ‘true’ when at least one element results in true when passed into the block Ex: p [3,4,7].any? { |el| el.even? } # => true Ex: p [3,5,7].any? { |el| el.even? } # => false .none?–return ‘true’ when no elements result in true when passed into the block. Ex: p[1,3,5].none? { |el| el.even? } # => true Ex: p[1,4,5].none? { |el| el.even? } # => false .one?–return ‘true’ when exactly one element results in…

array.map–allows us to take in an array and modify it a certain way. (Returns a new array!) (This can let us skip the step of shoveling a desired result into a new array[].) arr = [“a”, “b”, “c”, “d”] Old way: new_arr = [ ] arr.each { |ele| new_arr << ele.upcase + “!” } print new_arr puts Output: [“A!”, “B!”, “C!”, “D!”] New way with .map: arr = [“a”, “b”, “c”, “d”] #(.map is still an enumerable, so when we call it we have to pass in a block.) #This block accepts the element as well, like .each. new_arr = arr.map { |ele| ele.upcase + “!” } #In the block…