Ada：从文件中读取 [英] Ada: reading from a file

问题描述

我试图读取 Ada 中的 Long_Float 值的单个文件，如下所示： p>

 与Ada.Text_IO;使用Ada.Text_IO; 
与Ada.Long_Float_Text_IO; 
与Ada.Sequential_IO; 
 
 
过程Test_Read是
 
包Seq_Float_IO是新的Ada.Sequential_IO（Element_Type => Long_Float）; 
 
 Input_File：File_Type; 
值：Long_Float; 
 
 begin 
 
 Seq_Float_IO.Open（File => Input_File，Mode => Seq_Float_IO.In_File，Name =>fx.txt）; 
而不是End_OF_File（Input_File）循环
 Seq_Float_IO.Read（Input_File，value）; 
 Ada.Long_Float_Text_IO.Put（Item => value，Fore => 3，Aft => 5，Exp => 0）; 
结束循环; 
 Seq_Float_IO.close（File => Input_File）; 
 
 end Test_Read; 
  

我在编译时收到很多错误消息：

  17。 Seq_Float_IO.Open（File => Input_File，Mode => Seq_Float_IO.In_File，Name =>fx.txt）; 
 | 
>>>期望在第10行的实例的私人类型Ada.Sequential_Io.File_Type
>>>找到私人类型Ada.Text_Io.File_Type
 
 18.而不是End_OF_File（Input_File）循环
 19. Seq_Float_IO.Read（Input_File，value）; 
 | 
>>>期望在第10行的实例的私人类型Ada.Sequential_Io.File_Type
>>>找到私人类型Ada.Text_Io.File_Type
  

文件 fx.txt 包含例如：



  11.0 
 23.0 
 35.0 
 46.0 
  

任何帮助都将得到最多赞赏。

<使用Ada.Text_IO更新代码：

 使用Ada.Text_IO; 
 
 
过程Test_Read是
 
 Input_File：File_Type; 
值：字符; 
 
 begin 
 
 Ada.Text_IO.Open（File => Input_File，Mode => Ada.Text_IO.In_File，Name =>fx.txt）; 
 
而不是End_OF_File（Input_File）循环
 Ada.Text_IO.Get（File => Input_File，Item => value）; 
 Ada.Text_IO.Put（Item => value）; 
 Ada.Text_IO.New_Line; 
结束循环; 
 Ada.Text_IO.Close（File => Input_File）; 
 
 end Test_Read; 
  

但现在输出结果是：

  1 
 1 
。 
 0 
 2 
 3 
。 
 0 
 3 
 5 
。 
 0 
 4 
 6 
。 
  

问题在于 value 被定义为一个字符。如果我希望 value 的类型为 Long_Float ，那么我可以使用数字 11.0 ，23.0,35.0和46.0 后来在我的程序中，那么怎么去？

谢谢。

基本上，你正在实例化Sequential_IO来对表示（长）浮点数的二进制值做I / O操作。这不是你的文件中的内容。你的文件包含浮点数字的文本表示。在你的例子中，摆脱Sequential_IO并使用普通的Text_IO.Open打开文件，Long_Float_Text_IO到Get（）值
$ b

这就是为什么你会得到类型冲突错误消息，你试图对Long_Float_Text_IO File_Type变量执行Sequential_IO操作。

I am trying to read a file with a single column of Long_Float values in Ada as follows:

with Ada.Text_IO; use Ada.Text_IO;
with Ada.Long_Float_Text_IO;
with Ada.Sequential_IO;


procedure Test_Read is

  package Seq_Float_IO is new Ada.Sequential_IO (Element_Type => Long_Float);

  Input_File    : File_Type;
  value         : Long_Float;

begin

  Seq_Float_IO.Open (File => Input_File, Mode => Seq_Float_IO.In_File, Name => "fx.txt");
  while not End_OF_File (Input_File) loop
    Seq_Float_IO.Read (Input_File, value);
    Ada.Long_Float_Text_IO.Put (Item => value, Fore => 3, Aft  => 5, Exp  => 0);
  end loop;
  Seq_Float_IO.close (File => Input_File);

end Test_Read;

I do get lots of error messages on compilation:

17.       Seq_Float_IO.Open (File => Input_File, Mode => Seq_Float_IO.In_File, Name => "fx.txt");
                                     |
    >>> expected private type "Ada.Sequential_Io.File_Type" from instance at line 10
    >>> found private type "Ada.Text_Io.File_Type"

18.       while not End_OF_File (Input_File) loop
19.         Seq_Float_IO.Read (Input_File, value);
                               |
    >>> expected private type "Ada.Sequential_Io.File_Type" from instance at line 10
    >>> found private type "Ada.Text_Io.File_Type"

The file fx.txt contains for example:

11.0
23.0
35.0
46.0

Any help will be most appreciated.

Updated Code:

with Ada.Text_IO; use Ada.Text_IO;


procedure Test_Read is

   Input_File    : File_Type;
   value         : Character;

begin

   Ada.Text_IO.Open (File => Input_File, Mode => Ada.Text_IO.In_File, Name => "fx.txt");

   while not End_OF_File (Input_File) loop
      Ada.Text_IO.Get (File => Input_File, Item => value);
      Ada.Text_IO.Put (Item => value);
      Ada.Text_IO.New_Line;
   end loop;
   Ada.Text_IO.Close (File => Input_File); 

end Test_Read;

But now the output is:

1
1
.
0
2
3
.
0
3
5
.
0
4
6
.

The problem is that value is defined as a character. If I want value to be of the type Long_Float so that I can use the numbers 11.0, 23.0, 35.0 and 46.0 later on in my program, then how to go about?

Thanks.

解决方案

Basically, you're instantiating Sequential_IO to do I/O on binary values representing (long) floating point numbers. That's not what's in your file. Your file contains textual representations of floating point numbers.

In your example, get rid of Sequential_IO and use the plain Text_IO.Open to open the file and Long_Float_Text_IO to Get() values.

This is why you're getting the type conflict error messages, you're attempting to execute Sequential_IO operations on a Long_Float_Text_IO File_Type variable.

这篇关于Ada：从文件中读取的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！