how-haskell-improved-my-programming-skills.rb

# How learning Haskell changed my programming skill


# Pascal's triangle BEFORE Haskell:

def triangle_before_haskell iterations
  rows = []
  iterations.times { |r|
    new_row = [1]
    if r >= 1
      row = rows[r-1]
      (r-1).times { |i|
        new_row << row[i]+row[i+1]
      }
      new_row << 1
    end
    rows << new_row
  }
  rows
end

# took me 20 minutes or more, not knowing how to operate
# on arrays properly is the main issue here, also the code
# is not recursive


# Pascal's triangle AFTER learnign some Haskell:

def triangle depth, last_row = [1], triangle = [last_row]
  if depth == 1
    triangle
  else
    row = [1] + last_row.enum_cons(2).map { |a, b| a+b } + [1]
    triangle(depth-1, row, triangle+[row])
  end
end

# after learning some Haskell, this took me only 5 minutes to write.
# the code is recursive, much cleaner and since learning Haskell
# I know that it is very important to know what your language does for you



# both produce the same output

triangle_before_haskell(8).each { |row| puts row.inspect }
triangle(8).each { |row| puts row.inspect }