月: 2017年3月

defmodule Sales do
  def csv_to_list(filename) do
    {:ok, file} = File.open(filename, [:read])
    headers = (IO.read(file, :line) |> parse_csv_atom)
    IO.stream(file, :line)
    |> Enum.map(fn l -> parse_csv(l) end)
    |> Enum.map(fn sales -> Enum.zip(headers, sales) end)
  end

  defp parse_csv_atom(line) do
    String.trim(line, "\n")
    |> String.split(",")
    |> Enum.map(&String.to_atom/1)
  end

  defp parse_csv(line) do
    [id, ship_to, net_amount] = (String.trim(line, "\n") |> String.split(","))
    [String.to_integer(id), String.to_atom(String.trim(ship_to, ":")), String.to_float(net_amount)]
  end
end

IO.inspect Sales.csv_to_list("sales.csv")

^o^ > cat sales.csv
id,ship_to,net_amount
123,:NC,100.00
124,:OK,35.50
125,:TX,24.00
126,:TX,44.80
127,:NC,25.00
128,:MA,10.00
129,:CA,102.00
130,:NC,50.00

^o^ > elixir practice_11_7.exs
[[id: 123, ship_to: :NC, net_amount: 100.0],
 [id: 124, ship_to: :OK, net_amount: 35.5],
 [id: 125, ship_to: :TX, net_amount: 24.0],
 [id: 126, ship_to: :TX, net_amount: 44.8],
 [id: 127, ship_to: :NC, net_amount: 25.0],
 [id: 128, ship_to: :MA, net_amount: 10.0],
 [id: 129, ship_to: :CA, net_amount: 102.0],
 [id: 130, ship_to: :NC, net_amount: 50.0]]

defmodule Str do
  def capitalize(word) do
    String.to_charlist(word)
    |> to_upper([])
    |> to_string
  end

  defp to_upper([], result) do
    Enum.reverse(result)
  end
  defp to_upper([32|tail], result) do
    to_upper(tail, [32|result])
  end
  defp to_upper([?.|tail], result) do
    to_upper(tail, result)
  end
  defp to_upper([c|tail], result) do
    to_lower(tail, [upcase(c)|result])
  end
  defp upcase(c) when c <= ?Z, do: c
  defp upcase(c),              do: c - 32

  defp to_lower([], result) do
    Enum.reverse(result)
  end
  defp to_lower([32|tail], result) do
    to_lower(tail, [32|result])
  end
  defp to_lower([?.|tail], result) do
    to_upper(tail, [?.|result])
  end
  defp to_lower([c|tail], result) do
    to_lower(tail, [lowcase(c)|result])
  end
  defp lowcase(c) when c >= 97, do: c
  defp lowcase(c),              do: c + 32
end


IO.puts Str.capitalize("oh. a DOG. woof. ")

^o^ > elixir practice_11_6.exs
Oh. A dog. Woof.

defmodule Str do
  def center(slist) do
    len = longest(slist)
    slist
    |> Enum.map(fn s -> _center(s, len) end)
    |> Enum.each(&IO.puts/1)
  end

  defp longest(slist) do
    slist
    |> Enum.map(&String.length/1)
    |> Enum.max
  end

  defp _center(str, len) do
    l = div(len - String.length(str), 2)
    String.duplicate(" ", l) <> str
  end
end


Str.center(["cat", "zebra", "elephant"])

^o^ > elixir practice_11_5.exs
  cat
 zebra
elephant

defmodule Calculater do
  def calculate(charlist) do
    parse(charlist)
    |> calc
  end

  defp parse(charlist) do
    tokenize(charlist, [[]])
    |> _parse
  end

  defp tokenize([], result) do
    Enum.reverse(result)
  end
  defp tokenize([32|tail], result) do
    tokenize(tail, [[] | result])
  end
  defp tokenize([head|tail], [cur|rest]) do
    tokenize(tail, [cur ++ [head] | rest])
  end

  defp _parse([opnd1, op, opnd2]) do
    num1 = number(opnd1, 0)
    num2 = number(opnd2, 0)
    {op, num1, num2}
  end

  defp number([], value) do
    value
  end
  defp number([digit|tail], value) do
    number(tail, value * 10 + digit - ?0)
  end

  defp calc({'+', n1, n2}), do: n1 + n2
  defp calc({'-', n1, n2}), do: n1 - n2
  defp calc({'*', n1, n2}), do: n1 * n2
  defp calc({'/', n1, n2}), do: n1 / n2
end


IO.puts Calculater.calculate('123 + 27')
IO.puts Calculater.calculate('123 - 23')
IO.puts Calculater.calculate('100 * 2')
IO.puts Calculater.calculate('100 / 5')

^o^ > elixir practice_11_4.exs
150
100
200
20.0