This section of my program is supposed to list all files within the directory containing ".txt" in the name but it's not returning anything when run. If I delete ".txt" and leave it as an empty string "" then it works perfectly and returns all file names including the .txt files so I can't figure out what I'm doing wrong here.
procedure Search_Directory is
use Ada.Directories;
procedure Write_Search_Item(Search_Item : in Directory_Entry_Type) is
begin
Put(Item => Simple_Name(Directory_Entry => Search_Item));
New_Line;
end Write_Search_Item;
Filter : Constant Filter_Type := (Ordinary_File => True,
Special_File => False,
Directory => True);
begin
Search(Directory => Current_Directory,
Pattern => (".txt"),
Filter => Filter,
Process => Write_Search_Item'Access);
end Search_Directory;
The Search function, defined in the package Ada.Directories, takes a pattern argument which is either a null string or a form that is implementation-defined RM A.16 (111/ 2). In GNAT, this pattern is supposed to be a regular expression (see also here) described in System.Regexp (see also here, second grammar, a "globbing pattern").
Related
I have the following fragment of code
with GNAT.Command_Line; use GNAT.Command_Line;
with GNAT.Strings; use GNAT.Strings;
....
Define_Switch
(Config => Config, Output => File_Name'Access,
Long_Switch => "--file=", Switch => "-f=",
Help => "File with Composition");
....
Getopt
After parsing command line via Getopt I have access object that points to actual file name
I would like to copy this name to Ada.String.Fixed string that definded as
File_Name : String(1 .. 256);
I can print to console data from File_Name'Access as
Put_Line(File_Name.all);
I think I should provide something like copy operation then free access object.
How can I do it?
Thanks.
Alex
I guess File_Name in the code snippet defined as 'aliased GNAT.Strings.String_Access'. This is a "fat pointer" to the string object. "Fat" means it is not an address only, it is range of indices of the string. C-style Nil terminator is not used in Ada, and Nil is valid character.
You can copy data inside this string object into the another standard String object playing with indexes computations, but usually you must not do this: there is no Nil terminator, you will need to pass length of the actual data; destination string object may be smaller than necessary, and data will be truncated or exception raised; etc.
There are two right ways to do this. First one is to declare unconstrained string object and assign value to it.
declare
Fixed_File_Name : String := File_Name.all;
begin
Free (File_Name);
or use variable length string (bounded or unbounded):
declare
Unbounded_File_Name : Ada.Strings.Unbounded.Unbounded_String;
begin
Unbounded_File_Name :=
Ada.Strings.Unbounded.To_Unbounded_String (File_Name.all);
Free (File_Name.all);
Use of fixed string has important restriction: string object must be initialized exactly at the point of declaration of the object, and available only inside corresponding block/subprogram. Use of variable length string allows to declare string object outside of the scope of particular block/subprogram.
I am writing a school project to store string to the doubly linked list, but I don't know how to save the final list to a text file. I also what the user to choose the text file name. Can someone show me how to do that? Also for Ada can I have a not fixed-length string as input? Right now I set the string length to 5 but I really wanted to have a flexible length for the string. Below is my code thank you.
with Ada.Containers.Doubly_Linked_Lists;
with Ada.Text_Io; use Ada.Text_Io;
with Ada.Strings.Unbounded; use Ada.Strings.Unbounded;
with Ada.Integer_Text_IO; use Ada.Integer_Text_IO;
with Ada.IO_Exceptions;
procedure main is
type Command is (A, C, P, E, M);
package Command_IO is new Ada.Text_IO.Enumeration_IO (Command);
package String_List is new Ada.Containers.Doubly_Linked_Lists(Unbounded_String);
use String_List;
Userinput : String(1 .. 5) := (others => ' '); --This string length is 5
InsertLocation : String(1 .. 5) := (others => ' '); --This string length is 5
text : List; -- List is from Doubly_Linked_Lists
F : File_Type;
begin
loop
declare
Cmd : Command;
procedure Print(Position : Cursor) is -- this subprogram print all string from list
begin
Put_Line(To_String(Element(Position)));
--Put_Line("K");
end Print;
begin
Put_Line("*****************************");
Put_Line("*Enter A to add a text *");
Put_Line("*Enter C to insert a text *");
Put_Line("*Enter P the print text list*");
Put_Line("*Enter E the exit program *");
Put_Line("*Enter M to save the list *");
Put_Line("*****************************");
Put_Line(" ");
Put(">> ");
Command_IO.Get (Cmd);
Ada.Text_IO.Skip_Line;
Put_Line ("read " & Cmd'Image); -- ' to sort out the not-fully-Ada-aware syntax highlighting
Put_Line (" " );
case Cmd is
when a =>
Put_Line("Enter a text " );
Put(">> " );
Get(Userinput);
text.Append(To_Unbounded_String(Userinput)); -- if letter is a add it to the doubly link list
Put_line(" " );
when c =>
Put_Line("Enter a text location you want to insert " );
Put(">> " );
Get(Userinput);
Put_Line("Enter a text " );
Put(">> " );
Get(InsertLocation);
text.Insert(Before => text.Find(To_Unbounded_String(Userinput)), New_Item => To_Unbounded_String( InsertLocation ));
when p =>
text.Iterate(Print'access);
Put_line(" " );
when m =>
Put_Line("Save to file");
Create (F, Out_File, "file.txt");
Put_Line (F, "This string will be written to the file file.txt");
Close (F);
when e =>
Put_Line("Program Exit");
exit;
end case;
exception
when Ada.IO_Exceptions.Data_Error =>
Put_Line ("unrecognised command");
Put_Line (" ");
end;
end loop;
end main;
You look like you have all the parts. You can use Text_IO for writing to the file and you can use Unbounded_String to hold strings of any size. For reading in strings of any size, you can use the procedure Get_Line in Text_IO which returns a string of any length or if you really want to use Unbounded_Strings, you can use Ada.Text_IO.Unbounded_IO.Get_Line. I could also optionally suggest looking at Indefinite_Doubly_Linked_List instead of using Unbounded_String, depending on your use case.
For writing to file, just loop over the List and write each element to a file using Text_IO style functions.
Here is some scaffolding showing some of this.
with Ada.Text_IO; use Ada.Text_IO;
with Ada.Containers.Indefinite_Doubly_Linked_Lists;
use Ada.Containers;
procedure Hello is
package Lists is new Indefinite_Doubly_Linked_Lists(String);
Text : Lists.List;
begin
Put_Line("Hello, world!");
Put_Line("Enter a text:" );
declare
User_Input : String := Get_Line;
begin
Text.Append(New_Item => User_Input);
end;
Put_Line("Enter Text to Insert at:");
declare
Location : String := Get_Line;
begin
Put_Line("Enter New Text:");
declare
User_Input : String := Get_Line;
begin
Text.Insert(Before => Text.Find(Location), New_Item => User_Input);
end;
end;
-- Loop through list and write each element
for Line of Text loop
Put_Line(Line);
-- Write to file here using Text_IO file operations
end loop;
end Hello;
Side note, if you spend more time searching your data than you do creating your list, you can also look at Map packages. Ada has both hashed and ordered maps (with indefinite options as well).
A couple of observations:
(1) Although a String is a fixed-length object, the length can be determined at initialisation:
declare
Str : constant String := Get_Line;
begin
...
You may have to be a bit creative about using the value in Str outside its scope, the declare block. For example, if it’s the name of a file to be opened, the File_Type object to be opened could be in an outer scope.
(2) If you want to read an integer, use Ada.Integer_Text_IO.Get (followed by Skip_Line, because the Get terminates when the number has been read, leaving the rest of the line, including the terminator, in the input buffer)
Looks like you are on the right path.
A couple of points :
you can ask the user to enter a filename (e.g. in a funciton returning String, used to initialise a variable as in Simon's answer. This function could suggest a default which will be used if the user just presses Return. Then you pass that string to the Create call.
Probably the best way to output complex things like lists is to learn Stream I/O. This may be more complex to set up than you need right now, but ultimately it would let you simply "Write" the whole list to file in a single operation. Each data type has 'Read and 'Write attributes, which are procedures you can overload with your own procedures to format the file however you wish. The default 'Write attribute for a list will iterate over the whole List calling each element's own 'Write procedure. (It may also insert information about the List you don't want, that's why it's overloadable...)
Hi im just wondering how to put data in an array if i loop txt and store it in A_Composite Name.
procedure Main is
type An_Array is array (Natural range <>) of A_Composite;
type A_Composite is
record
Name : Unbounded_String;
end record;
File : Ada.Text_IO.File_Type;
Line_Count : Integer := 0;
begin
Ada.Text_IO.Open (File => File,
Mode => Ada.Text_IO.In_File,
Name => "highscore.txt");
while not Ada.Text_IO.End_Of_File (File) loop
declare
Line :String := Ada.Text_IO.Get_Line (File);
begin
--I want to store Line String to array. but i don't know how to do it
end;
end loop;
Ada.Text_IO.Close (File);
end Main;
Ok, you have an unconstrained array here. This has implications; you see an unconstrained array gains its definite length when the object (general sense, not OOP) is declared or initialized.
As an example, let's look at strings (which are unconstrained arrays of characters) for an example to see how this works:
-- Create a string of 10 asterisks; the initialization takes those bounds.
A : constant string(1..10):= (others => '*');
-- Create a string of 10 asterisks; but determined by the initialization value.
B : constant string := (1..10 => '*');
-- Another way of declaring a string of 10 asterisks.
C : constant string := ('*','*','*','*','*','*','*','*','*','*');
Now, you can get these bounds from a function call; this means that we can use function-calls to return these values recursively.
Function Get_Text return An_Array is
Package Unbounded renames Ada.Strings.Unbounded;
-- You'll actually want the Get_Line that takes a file.
Function Get_Line return Unbounded.Unbounded_String
renames Unbounded.Text_IO.Get_Line;
begin
return (1 => (Name => Get_Line)) & Get_Text;
exception
when End_Error => return ( 1..0 => (Name => Unbounded.Null_Unbounded_String) );
end Get_Text;
So, that's how you'd do it using an unconstrained array.
I'm trying to return string "<a>" , but I received empty string.
That is,
"<a>" => (nothing but not nil)
"PP<a>" => PP
"R".."<a>" => R
"R:" .. (string.format("<%s>", "a")) => R
I haven't found in documentation this feature.
Can you help my understand why this happens?
It might be because you're viewing it in an application where the HTML tags are parsed. You'd need to escape the < and > characters:
"<a>"
I've been using Ada.Containers.Indefinite_Hased_Maps to create my own custom hashed maps, and it worked quite well until I tried to use a vector as the element type. Here is an example of the problematic code:
package String_Vectors is new Ada.Containers.Vectors(Element_Type => Unbounded_String, Index_Type => Natural);
subtype String_Vector is String_Vectors.Vector;
package Positive2StringVector_HashMaps is new Ada.Containers.Indefinite_Hashed_Maps --Compiler fails here
(Element_Type => String_Vector,
Key_Type => Positive,
Hash => Positive_Hash,
Equivalent_Keys => Positive_Equal);
Basically, I cannot Positive2StringVector_HashMaps package, because the compiler comes up with:
no visible subprogram matches the specification for "="
From what I understand, it isn't finding the equality operator for the String_Vector , am I correct? If I am, what is the proper way of implementing it? And if I'm not, what am I doing wrong??
You don’t need to implement
function “=“ (L, R : String_Vectors.Vector) return Boolean
yourself, because there already is one in String_Vectors; see ALRM A.18.2(12). So you write
package Positive2StringVector_HashMaps is new Ada.Containers.Indefinite_Hashed_Maps
(Element_Type => String_Vector,
Key_Type => Positive,
Hash => Positive_Hash,
Equivalent_Keys => Positive_Equal,
“=“ => String_Vectors.”=");
By the way, is there some reason you used Ada.Containers.Vectors on Unbounded_String rather than Indefinite_Vectors on String? (wanting to change the length of a contained string would count as a Good Reason!)