Question

如何在Elixir或Erlang中执行字符串replace_at？

例如，给定此固定宽度文件：

EmployeeFundMappingID EmployeeID  FundID      IsActive EntryDate               ExitDate                ExitTypeID  DateCreated             CreatedByID DateModified            ModifiedByID ConfirmedBy DateConfirmed           GUID                                     IsPooled DatePooled
1                     1118544     1           1        2009-04-20 00:00:00.000 NULL                    NULL        2014-05-17 08:46:48.020 1           2014-10-30 13:34:47.177 NULL         1           2009-04-20 17:48:12.067 NULL                                     NULL     NULL
2                     1027350     1           1        2008-03-03 00:00:00.000 NULL                    NULL        2014-05-17 08:46:48.020 1           2014-10-30 13:34:47.177 NULL         1           2008-05-04 15:13:30.303 NULL                                     NULL     NULL
3                     1024795     1           1        2008-02-29 00:00:00.000 NULL                    NULL        2014-05-17 08:46:48.020 1           2014-10-30 13:34:47.177 NULL         1           2008-05-04 15:13:30.303 NULL                                     NULL     NULL
4                     1116497     1           1        2009-03-24 00:00:00.000 NULL                    NULL        2014-05-17 08:46:48.020 1           2014-10-30 13:34:47.177 NULL         1           2009-03-24 13:00:15.277 NULL                                     NULL     NULL
5                     1116569     1           1        2009-03-24 00:00:00.000 NULL                    NULL        2014-05-17 08:46:48.020 1           2014-10-30 13:34:47.177 NULL         1           2009-03-24 14:43:08.280 NULL                                     NULL     NULL
6                     1116920     1           1        2009-03-27 00:00:00.000 NULL                    NULL        2014-05-17 08:46:48.020 1           2014-10-30 13:34:47.177 NULL         1           2009-03-27 17:16:35.073 NULL                                     NULL     NULL

col位置：

[0, 22, 34, 46, 55, 79, 103, 115, 139, 151, 175, 188, 200, 224, 265, 274]

我们如何在每个col位置用\s替换\t？

我正在尝试将Fixed-Width文件转换为csv

Answer 1

我会使用一组函数来减少原始行，从而改变字符串中的各个位置。

funs =
  [22, 34, 46, 55, 79, 103, 115, 139, 151, 175, 188, 200, 224, 265, 274]
  |> Enum.map(& &1 - 1)
  |> Enum.map(fn len ->
       fn <<s :: binary-size(len), " ", rest :: binary>> ->
         s <> "\t" <> rest
       end
     end)

input
|> String.trim
|> String.split("\n")
|> Enum.map(fn line ->
     Enum.reduce(funs, line, fn fun, acc -> fun.(acc) end)
   end)

这可能是使用生成的宏，每个位置一次和递归调用以更优雅的方式完成的，但是在函数列表中减少对我来说更直接。

这种方法的优势在于它可以立即对任何不一致的数据进行失败，确保（或多或少）如果通过，转换工作正确完成，与其他所有更短的解决方案不同。

它也比任何Regex解决方案都快得多。

由于这将应用于16M行，这里可能是性能最高的版本，它一次匹配整行：

input
|> String.trim
|> String.split("\n")
|> Enum.map(
     # [22, 34, 46, 55, 79, 103,
     #  115, 139, 151, 175, 188,
     #  200, 224, 265, 274]
     # note: this assumes the listed positions above are 1-based
     fn <<
        c1 :: binary-size(21),
        " ",
        c2 :: binary-size(11),
        " ",
        c3 :: binary-size(11),
        " ",
        c4 :: binary-size(8),
        " ",
        c5 :: binary-size(23),
        " ",
        c6 :: binary-size(23),
        " ",
        c7 :: binary-size(11),
        " ",
        c8 :: binary-size(23),
        " ",
        c9 :: binary-size(11),
        " ",
        c10 :: binary-size(23),
        " ",
        c11 :: binary-size(12),
        " ",
        c12 :: binary-size(11),
        " ",
        c13 :: binary-size(23),
        " ",
        c14 :: binary-size(40),
        " ",
        c15 :: binary-size(8),
        " ",
        c16 :: binary
        >> ->
     c1 <> "\t" <> 
       c2 <> "\t" <> 
       c3 <> "\t" <> 
       c4 <> "\t" <> 
       c5 <> "\t" <> 
       c6 <> "\t" <> 
       c7 <> "\t" <> 
       c8 <> "\t" <> 
       c9 <> "\t" <> 
       c10 <> "\t" <> 
       c11 <> "\t" <> 
       c12 <> "\t" <> 
       c13 <> "\t" <> 
       c14 <> "\t" <> 
       c15 <> "\t" <> 
       c16
   end)

Answer 2

您可以做的是先加入日期时间，然后用逗号替换所有空格，然后将日期时间恢复为原始格式：

$this->sendemail($request); // $this just because it is on same controller or basecontroller

// For example
public function saveInvoice(Request $request){
    .
    .
    .
    $sendMail = $this->sendemail($request);
    if($sendMail == 'success'){
        // On success
    } else {
        // On Error 
    }
} 
public function sendemail(Request $request) {
    .
    .
    .
    return 'success';
}

Answer 3

比较超过16M行的数据集上的两个实现：

  def flat2csv1(src, dst) do
    Logger.info("START")

    t = System.system_time(:millisecond)

    funs =
      [12, 52, 76]
      |> Enum.map(&(&1 - 1))
      |> Enum.map(fn len ->
        fn <<s::binary-size(len), " ", rest::binary>> ->
          s <> "\t" <> rest
        end
      end)

    File.stream!(src)
    |> Enum.map(fn line ->
      Enum.reduce(funs, line, fn fun, acc -> fun.(acc) end)
    end)
    |> write(dst)

    log_elapsed("DONE", t)
  end

  def flat2csv0(src, dst) do
    Logger.info("START")

    t = System.system_time(:millisecond)

    File.stream!(src)
    |> Enum.map(fn <<
                     c1::binary-size(11),
                     " ",
                     c2::binary-size(39),
                     " ",
                     c3::binary-size(23),
                     " ",
                     ce::binary
                   >> ->
      c1 <> "\t" <> c2 <> "\t" <> c3 <> "\t" <> ce
    end)
    |> write(dst)

    log_elapsed("DONE", t)
  end

  defp log_elapsed(s, t) do
    t = System.system_time(:millisecond) - t
    Logger.debug("#{s}: #{t} ms")
  end

  defp write(s, dst) do
    File.write!(dst, s, [:append])
  end

结果

# flat2csv0
11:40:25.055 [info] START
11:42:26.028 [info] DONE: 120969 ms

# flat2csv1
11:45:17.521 [info] START
11:48:25.433 [info] DONE: 187906 ms

如何用另一个[ELIXIR / ERLANG]替换字符串中的第n个字符

3 个答案: