Ruby: Map Function to List

By Xah Lee. Date:

Map Function to List

Use array.map {…} method on array object to create a new array. Example:

# -*- coding: utf-8 -*-
# ruby

def ff(n)
 n*n
end

aa = 0..4 # array 0 to 4

p aa.map {|xx| ff xx} # [0, 1, 4, 9, 16]

Use method array.map! {…} to have the original array modified.

Removing Elements in a List

To remove elements, use “select” method and pass it a block.

In Ruby, many methods can take a “block” argument. The “block” is a kind of lambda expression. The syntax has the form: object_name.method_name { |x| expression_on_x}. Example:

# -*- coding: utf-8 -*-
# ruby

aa = 0..10 # a array 0 to 10

p aa.select { |xx| xx % 2 == 0 } # [0, 2, 4, 6, 8, 10]

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  1. Ruby Basics
  2. Doc Lookup
  3. Print Version String
  4. Unicode 💎
  5. Quote String
  6. Quote Long String
  7. Format String
  8. String Operations
  9. True, False
  10. “if then else”
  11. for, while, Loop
  12. List
  13. Loop Thru List
  14. Hash Table
  15. Function Optional Parameter
  16. Map f to List
  17. Complex Numbers
  18. Intro to Reading Ruby Doc: What's M, C, ::, # ?
  19. Predefined Global Variables
  20. What's RVM, Gem, Rake, Bundler, RDoc, ri, irb?