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generics - Ada 含糊不清的表达与 Get

问题描述

我正在尝试使用 IOredirection 来创建、添加、删除和打印两个数组，一个整数和一个使用泛型的浮点数。

整数数组的情况很好，但是在“get(fVal)”时，我收到错误“模糊表达式（无法解析“Get”）。

我认为这可能与浮点数组在整数数组之后有关。我把它放在整数数组之前，但浮点数组仍然出现同样的错误。

我对 Ada 还是很陌生，所以有时我很难掌握它。

with Ada.Text_IO;
use Ada.Text_IO;
with Ada.Float_Text_IO;
use Ada.Float_Text_IO;
with CreateList;

procedure Main is

   package IntIO is new Ada.Text_IO.Integer_IO(Integer); use IntIO;
   package FloatIO is new Ada.Text_IO.Float_IO(Float); use FloatIO;

begin

   declare
      max: integer;   --declaring integer named "max"
      val: integer;
      del: integer;
      pointer : integer := 0;
      len : integer := 0;
      procedure MyPut(x: integer) is begin
            IntIO.Put(x, 0, 10);
      end MyPut;

      package C_List is new CreateList(max, integer, MyPut); use C_List;

   begin
      get(max);                              --assigns input for array size and assigns value to "max"
      for row in 1 .. max loop
         get(val);
         C_List.add_to_list(val);            --calls procedure to add value 12 to array
      end loop;
      C_List.print_list;                     --calls procedure to print entire array
      len := C_List.length_of_list;          --calls function to determine the current length of array and assign the value to "len"
      for pointer in 1 .. len loop           --calls procedure to print individual value in array. Loops to print all values in array
         C_List.print_list(pointer);
      end loop;
      Put_Line("");
      get(del);
      C_List.delete_from_list(del);          --calls procedure to delete a value from array
      C_List.print_list;                     --calls procedure to print entire array
   end;

   

   declare
      max: integer;   --declaring integer named "max"
      fVal: float;
      del: integer;
      pointer : integer := 0;
      len : integer := 0;
      
      procedure MyPut(x: Float) is begin
         FloatIO.Put(x, 0, 0, 0);
      end MyPut;


      package B_List is new CreateList(max, float, MyPut); use B_List;

      begin
         get(max);                           --assigns input for array size and assigns value to "max"
      for row in 1 .. max loop
         get(fVal);
         B_List.add_to_list(fVal);           --calls procedure to add value 12 to array
      end loop;
         B_List.print_list;                  --calls procedure to print entire array
         len := B_List.length_of_list;       --calls function to determine the current length of array and assign the value to "len"
         for pointer in 1 .. len loop        --calls procedure to print individual value in array. Loops to print all values in array
            B_List.print_list(pointer);
         end loop;
         Put_Line("");
         get(del);
         B_List.delete_from_list(del);       --calls procedure to delete a value from array
         B_List.print_list;                  --calls procedure to print entire array
      end;

end Main;

创建列表.adb

with Ada.Text_IO;
use Ada.Text_IO;
with Ada.Float_Text_IO;
use Ada.Float_Text_IO;

package body CreateList is
   len: Integer;                       --declaring integer named "len"
   list: array(1..max) of itemType;    --making an integer array named "list"
   pnt: integer;                       --declaring integer named "pnt"

   procedure add_to_list (ListItem: in itemType) is begin   --procedure that adds new integer value to array "list"
      if pnt >= max then                                    --detects when array is full and can't fit more values
         Put_Line("**Detected Overflow**");
      else
         pnt := pnt + 1;                                    --moves pointer
         list(pnt) := ListItem;                             --adds new integer value to pointer index
      end if;
   end add_to_list;

   procedure delete_from_list (indx: in Integer) is begin   --procedure that removes an integer value from array "list"
      if indx = 0 then                                      --detects when array is empty and doesn't have any values to delete
         Put_Line("**Detected Underflow**");
      else
         for j in indx .. (pnt - 1) loop                    --loop to pop the stack after an integer has been removed from array
            if j < len then
               list(j) := list(j + 1);
            end if;
         end loop;

         pnt := pnt - 1;
      end if;
   end delete_from_list;

   function length_of_list return Integer is begin   --function to determine the current number of integers in array
      for i in 1 .. pnt loop
         len := len + 1;
      end loop;
      return len;
   end length_of_list;

   procedure print_list (indx: in Integer) is begin   --procedure that prints the integer at a given index of the array
      Put(list(indx));
      Put(" ");
   end print_list;

   procedure print_list is begin   --procedure that prints the entire array
      for i in 1 .. pnt loop
         Put(list(i));
         Put(" ");
      end loop;
      Put_Line("");
   end print_list;

begin
   pnt := 0;
   len := 0;

end CreateList;

创建列表.ads

generic
   max: integer;
   type itemType is private;
   
   with procedure Put(x: itemType);

package CreateList is
      
   procedure add_to_list (listItem: in itemType);
   --   
   procedure delete_from_list (indx: in Integer);
   --   
   function length_of_list return Integer;
   --
   procedure print_list (indx: in Integer);
   procedure print_list;

end CreateList;

谢谢@thindil。我将 get(fVal) 更改为 FloatIO.get(fVal) 并且它起作用了。

标签： genericsadaio-redirection

解决方案

您收到此消息的原因是您有两个为Float提供put的包：

  • 您的Ada.Text_IO.Float_IO (Float)实例化名为FloatIO

  • 名为Ada.Float_Text_IO的浮点标准包

根据您的需要，您可以同时使用和前缀或仅使用Ada.Float_Text_IO，因为您没有特定的浮点类型。

这些在错误消息中并不容易看到：

main.adb:23:40: warning: "max" may be referenced before it has a value
main.adb:61:10: ambiguous expression (cannot resolve "Get")
main.adb:61:10: possible interpretation at a-tiflio.ads:57, instance at line 9
main.adb:61:10: possible interpretation at a-tiflio.ads:57, instance at a-flteio.ads:20
gnatmake: "main.adb" compilation error

唯一的线索是最后一行说明解释来自 a-flteio.ads 中第 20 行的实例，它是Ada.Float_Text_IO的文件名。

请注意，即使Ada.Float_Text_IO是一个看起来像您的实例（即new Ada.Text_IO.Float_IO (Float)），但从编译器的角度来看，它并不是同一个包。

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