I'm in the process of making my own package for an Ada main program. I read a string followed by an integer and another string and the problem is I need to cut the first string at sign of first space. I don't know how to do it and I've searched stack overflow only to find solutions in other languages.
My code right now in the package body is:
Get_Line(Item.String, Item.X1)
where X1 is an integer and String is the string. This works if you define the length in the type to match the exact length of your input but of course you want to be able to insert whatever you want and thus it doesn't work.
Can somebody point me in the right direction?
Thanks
Why do you need to make a package for an Ada main program? Most compilers need them to be parameterless library-level procedures.
Anyway, this might give you some tips.
with Ada.Text_IO;
with Ada.Integer_Text_IO;
procedure Agrell is
begin
declare
Line : constant String := Ada.Text_IO.Get_Line;
This is how to deal with reading a string of unknown length. You have to work out how to preserve it for future use (maybe use an Unbounded_String?)
The_Integer : Integer;
begin
Looking_For_Space :
for J in Line'Range loop
if Line (J) = ' ' then
Everything from Line’First to J - 1 is the string you wanted.
declare
Dummy : Positive;
begin
Ada.Integer_Text_IO.Get (From => Line (J .. Line'Last),
Item => The_Integer,
Last => Dummy);
end;
OK, now we have The Integer...
...
exit Looking_For_Space;
... and we’re done with the first line.
end if;
end loop Looking_For_Space;
end;
end Agrell;
Related
I am learning Ada (by trying https://adventofcode.com/2018/ problems). To start with, I am trying to develop a number of "utility" packages that will help with text processing etc.
I have successfully written a function that will read from stdin and return an array of Unbounded_Strings for each input line.
I am trying to modify that function to do the same, but instead convert each Unbounded_String to an Integer before insertion into the array.
Here is my package:
get_stdin.ads:
with Ada.Strings.Unbounded;
package get_stdin is
type IntegerArray is array (Natural range <>) of Integer;
function get_ints return IntegerArray;
end get_stdin;
get_stdin.adb:
with Ada.Text_IO;
with Ada.Text_IO.Unbounded_IO;
with Ada.Strings.Unbounded;
with Ada.Strings;
package body get_stdin is
function get_ints return IntegerArray is
Counter : Natural := 0;
Str : Ada.Strings.Unbounded.Unbounded_String;
Arr : IntegerArray(0..10000);
begin
while not Ada.Text_IO.End_Of_File loop
Str := Ada.Text_IO.Unbounded_IO.Get_Line;
Arr(Counter) := Integer'Value(Ada.Strings.Unbounded.To_String(Str));
Counter := Counter + 1;
end loop;
return Arr(0..Counter-1);
end get_ints;
end get_stdin;
I am calling using this package inside this procedure:
procedure d1 is
StdinArr : get_stdin.IntegerArray := get_stdin.get_ints;
begin
null; -- Array processing to follow
end;
This successfully compiles, and I then pipe in my input text file:
me#mypc /cygdrive/c/Users/me/aoc2018
$ cat d1.txt
-6
-1
-18
-10
...etc
me#mypc /cygdrive/c/Users/me/aoc2018
$ cat d1.txt | ./d1.exe
raised CONSTRAINT_ERROR : bad input for 'Value: "-6"
"-6" is the first value in the text file. My string-to-integer conversion code was essentially copied from this question.
I am not sure why a bad input error is raised.
It raises the same error if I replace -6 with a positive integer in the file
This is running under Cygwin on Windows 10.
Compiled/linked with gnatmake version 7.3.0
Note: I'm just getting started with Ada so there's probably lots of issues with my code in general.
What am I doing wrong and how can I fix this function/package to return my IntegerArray type correctly filled with Integers?
This was a line endings issue. I was running under cygwin on Windows 10. My text file has Windows-style line endings.
Using dos2unix:
$ cat d1.txt | dos2unix.exe | ./d1.exe
was sufficient to make it work correctly.
If anyone can explain precisely why, that would be interesting. I'm guessing that Get_Line only strips off the \n character, not the \r.
So I can easily grab the int value I am looking for from my .txt file through standard input but when there is a white space (or multiple white spaces) before it, it doesn't work and a data error occurs, Since its an integer though, my code below which works for a grabbing a string, does not work when I put an int in there because you cannot compare an Int to a String. Any ideas on workarounds?
Until_loop: -- Loop to get chars even if space is between
loop
get(int_variable);
exit Until_loop when int_variable) /= " "; --won't work
end loop Until_loop;
ajb was right integers already go the space checking, my code was only messing it up. No loop needed for getting ints but it works well for String's/Characters.
So you can use the 'Value attribute to go from string to int and 'Image to go from int to string. These are attributes in Ada. Learning how to effectively use attributes will definitely increase your Ada productivity.
Basically I think this does what you want. You can read the string in and convert the string to an integer with
with Ada.Text_IO; use Ada.Text_IO;
procedure Foo is
Str: String(1 .. 10) := (others => ' ');
Last_Char : Integer;
begin
Put("Enter num: ");
Get_Line(Str, Last_Char);
Put_Line("Str = """ & Str & """");
Put_Line("Last = " & Integer'Image(Last_Char));
Put_Line("The num is " & Integer'Value(Str));
end Foo;
It yields the output:
Enter num: 1239
Str = "1239 "
Last_Char = 4
The num is 1239
If you want help iterating on this idea and morphing your original question into a slightly different method, let me know. I will gladly work with you on this ;)
I am attempting to understand how to fix this circular dependency. All the examples I can find online suggest using a limited with, but then they demonstrate the use with two basic types, whereas this is a bit more advanced. The circular dependency is between the two files below. I thought it was between package Chessboard ... and the Piece type, but now I am not so sure. Attempting to put the package Chessboard ... line within chess_types.ads after the Piece type is declared and removing the use and with of Chessboard results in an error: this primitive operation is declared too late for the Move procedure. I am stuck on how to get out of this dependency. Any help would be much appreciated!
Thank you
chessboard.ads:
with Ada.Containers.Indefinite_Vectors;
use Ada.Containers;
with Chess_Types;
use Chess_Types;
package Chessboard is new Indefinite_Vectors(Board_Index, Piece'Class);
chess_types.ads:
with Ada.Containers.Indefinite_Vectors;
use Ada.Containers;
with Chessboard;
use Chessboard;
package Chess_Types is
subtype Board_Index is Integer range 1 .. 64;
type Color is (Black, White);
type Piece is tagged
record
Name : String (1 .. 3) := " ";
Alive : Boolean := False;
Team : Color;
Coordinate : Integer;
end record;
procedure Move_Piece(Board: in Vector; P: in Piece; Move_To: in Integer);
end Chess_Types;
More Code for question in comments:
Chess_Types.Piece_Types.ads:
package Chess_Types.Piece_Types is
type Pawn is new Piece with
record
First_Move : Boolean := True;
end record;
overriding
procedure Move_Piece(Board: in CB_Vector'Class; Po: in Pawn; Move_To: in Board_Index);
-- Other piece types declared here
end Chess_Types.Piece_Types;
Chess_Types.Piece_Types.adb:
with Ada.Text_IO;
use Ada.Text_IO;
package body Chess_Types.Piece_Types is
procedure Move_Piece(Board: in CB_Vector'Class; Po: in Pawn; Move_To: in Board_Index) is
Index_From, Index_To : Board_Index;
Move_From : Board_Index := Po.Coordinate;
begin
-- Obtain locations of Pawn to move from (Index_From) and to (Index_To)
-- in terms of the single dimension vector
for I in Board.First_Index .. Board.Last_Index loop
if Board.Element(I).Coordinate = Move_From then
Index_From := I;
end if;
if Board.Element(I).Coordinate = Move_To then
Index_To := I;
end if;
end loop;
-- Determine if the requested move is legal, and if so, do the move.
-- More possibilties to be entered, very primitive for simple checking.
if Move_To - Move_From = 2 and then Po.First_Move = True then
Board.Swap(I => Index_From, J => Index_To); -- "actual for "Container" must be a variable"
Board.Element(Index_From).First_Move := False; -- "no selector for "First_Move" for type "Piece'Class"
elsif Move_To - Po.Coordinate = 1 then
Board.Swap(Index_From, Index_To); -- "actual for "Container" must be a variable"
end if;
-- Test to make sure we are in the right Move_Piece procedure
Put_Line("1");
end Move_Piece;
-- Other piece type move_piece procedures defined here
end Chess_types.Piece_Types;
As a note to understand further, the Coordinate component of each piece correspond to ICCF numeric notation, which is two digits, so there needs to be some type of conversion between the vector and the ICCF notation, hence the reason for the whole for loop at the start.
This is a tough one. It looks like limited with and generics don't play nice together. The only way to make it work is to go back to using your own access type:
with Ada.Containers.Vectors;
use Ada.Containers;
limited with Chess_Types;
use Chess_Types;
package Chessboard_Package is
subtype Board_Index is Integer range 1 .. 64;
type Piece_Acc is access all Piece'Class;
package Chessboard is new Vectors(Board_Index, Piece_Acc);
end Chessboard_Package;
I had to put the instantiation into a new package, and move the Board_Index there too. Also, I changed it to Vectors since Piece_Acc is a definite type and there's no point in using Indefinite_Vectors. But in any event, this defeats the purpose. I'm just not sure Ada gives you a way to do what you want with two packages like this.
Even doing it in one package is not easy:
with Ada.Containers.Indefinite_Vectors;
use Ada.Containers;
package Chess_Types is
subtype Board_Index is Integer range 1 .. 64;
type Color is (Black, White);
type Piece is tagged record ... end record;
type CB_Vector is tagged;
procedure Move_Piece (Board : in CB_Vector'Class;
P : in Piece;
Move_To : in Board_Index);
package Chessboard is new Indefinite_Vectors(Board_Index, Piece'Class);
type CB_Vector is new Chessboard.Vector with null record;
end Chess_Types;
This compiles, but I had to add extra stuff to get around some of the language rules (in particular, when you instantiate a generic, that "freezes" all prior tagged types so that you can no longer declare a new primitive operation of the type); also, I had to make the Board parameter a classwide type to avoid running into the rule about primitive operations of multiple tagged types.
As I understand it, this will do what you want.
with Ada.Containers.Indefinite_Vectors;
use Ada.Containers;
package Chess_Types is
subtype Board_Index is Integer range 1 .. 64;
type Color is (Black, White);
type Piece is abstract tagged
record
Name : String (1 .. 3) := " ";
Alive : Boolean := False;
Team : Color;
Coordinate : Board_Index;
end record;
type Piece_Ptr is access all Piece'Class;
package Chessboard is new Indefinite_Vectors(Board_Index, Piece_Ptr);
procedure Move_Piece (Board : in Chessboard.Vector;
P : in Piece'Class;
Move_To : in Board_Index) is abstract;
end Chess_Types;
NOTES:
Piece is now abstract, as is the Move_Piece method. This will mean you now need to derive your other piece types (package piece_type-rook.ads, with a move_piece method for rook) etc...
Chessboard now contains pointers (Class wide pointers), beware allocating, deallocating, deep copy, shallow copy issues when using it.
You should now be able to call Move_Piece on any dereference of a piece_ptr and have it dispatch to the correct method.
The Move_To parameter is now the same type as the Board_Index. (Coordinate also brought in line) -- this seems a bit clunky, perhaps rethink this. (Row & Column Indices defining a 2D array perhaps? --No need for Indefinite_Vectors)
To answer the second question in the comment:
To use First_Move, the procedure has to know that it's a Pawn. If the object is declared with type Piece'Class, you can't access components that are defined only for one of the derived types. (That's true in most OO languages.) This may indicate a flaw in your design; if you have a procedure that takes a Piece'Class as a parameter, but you want to do something that makes sense only for a Pawn, then maybe you should add another operation to your Piece that does a default action for most pieces (perhaps it does nothing) and then override it for Pawn. Other possibilities are to use a type conversion:
procedure Something (P : Piece'Class) is ...
if Pawn(P).First_Move then ...
which will raise an exception if P isn't a Pawn. If you want to test first, you can say "if P in Pawn". I sometimes write code like:
if P in Pawn then
declare
P_Pawn : Pawn renames Pawn(P);
begin
if P_Pawn.First_Move then ...
end;
end if;
But defining a new polymorphic operation is preferable. (Note: I haven't tested the above code, hope I didn't make a syntax error somewhere.)
I'm an absolute beginner in Ada and I'm trying to calculate sin(x) [sin(3) now] by using Taylor-series, but I just can't get it to work.
So here is my procedure:
with Ada.Float_Text_IO;
with Mat;
procedure SinKoz is
X:Float:=3.0;
Szamlalo:Float:=0.0;
begin
for I in 1..100 loop
Szamlalo := Szamlalo + ((-1.0)**I)*(X**(2.0*I+1.0))/Mat.Faktorialis(2*I+1);
end loop;
Ada.Float_Text_IO.Put( Szamlalo );
end SinKoz;
And inside Mat, here is my Faktorialis, which calculates the factorial of 2*I+1:
function Faktorialis( N: Float ) return Float is
Fakt : Float := 1.0;
begin
for I in 1..N loop
Fakt := Fakt * I;
end loop;
return Fakt;
end Faktorialis;
When i'm trying to compile my code, this error comes up:
exponent must be of type Natural, found type "Standard.Float"
I hope you can help me trying to figure out what went wrong with my types!
The first question is : do you need to raise X to a non-integer power?
It looks to me as if you don't : in which case replace X**(2.0*I+1.0) with X**(2*I+1) and all will be well.
But if you really do (perhaps not here, but in another application) you just need to make such an operator visible : there's one for Float in the package Ada.Numerics.Elementary_Functions so precede your function with
with Ada.Numerics.Elementary_Functions;
use Ada.Numerics.Elementary_Functions;
and it should work as written.
Finally, if you have created your own float type, you can instantiate the generic package Ada.Numerics.Generic_Elementary_Functions with your type as its parameter, to create a set of these functions specifically for your type.
Gotta love Ada's strong typing.
Off the top of my head, I suspect your problem may be this line:
Szamlalo := Szamlalo + ((-1.0)**I)*(X**(2.0*I+1.0))/Mat.Faktorialis(2*I+1);
2.0*I+1.0 is going to return a Float. Not a Natural. You could try wrapping that in Integer() or Natural() (Natural is a subtype of Integer) and see if that helps.
I have a function that returns a string for a particular item, and I need to call that function numerous times and combine those strings into one. The combined string is bounded. I've made sure to fill it when space characters when it initializes but I keep getting "length check failed" errors. Is there something basic I'm doing wrong here?
FOR I IN 1..Collection.Size LOOP
Combined_String := combined_string & Tostring(Collection.Book(I));
END LOOP;
Unbounded_String is probably the easiest way to go:
with Ada.Strings.Unbounded;
use Ada.Strings.unbounded;
...
Temp_Unbounded_String : Unbounded_String; -- Is empty by default.
...
for I in 1 .. Collection.Size loop
Append(Temp_Unbounded_String, ToString(Collection.Book(I));
end loop;
If you then need to have the result placed in your fixed length standard string:
declare
Temp_String : constant String := To_String(Temp_Unbounded_String);
begin
-- Beware! If the length of the Temp_String is greater than that of the
-- fixed-length string, a Constraint_Error will be raised. Some verification
-- of source and target string lengths must be performed!
Combined_String(Temp_String'Range) := Temp_String;
end;
Alternatively, you can use the Ada.Strings.Fixed Move() procedure to bring the Unbounded_String into the target fixed-length string:
Ada.Strings.Fixed.Move(To_String(Temp_Unbounded_String), Combined_String);
In this case, if the source string is "too long", by default a Length_Error exception is raised. There are other parameters to Move() that can modify the behavior in that situation, see the provided link on Move for more detail.
In order to assign Combined_String, you must assign the full correct length at once. You can't "build up" a string and assign it that way in Ada.
Without seeing the rest of your code, I think Ada.Strings.Unbounded is probably what you should be using.
I know this is an ancient question, but now that Ada 2012 is out I thought I'd share an idiom I've been finding myself using...
declare
function Concatenate(i: Collection'index)
is
(tostring(Collection(i) &
if (i = Collection'last) then
("")
else
(Concatenate(i+1))
);
s: string := Concatenate(Collection'first);
begin
Put_Line(s);
end;
Typed off the top of my head, so it'll be full of typos; and if you want it to work on empty collections you'll need to tweak the logic (should be obvious).
Ada 2012's expression functions are awesome!
Ada works best when you can use perfectly-sized arrays and strings. This works wonderfully for 99% of string uses, but causes problems any time you need to progressively build a string from something else.
Given that, I'd really like to know why you need that combined string.
If you really need it like that, there are two good ways I know of to do it. The first is to use "unbounded" (dynamically-sized) strings from Ada.Strings.Unbounded, as Dave and Marc C suggested.
The other is to use a bit of functional programming (in this case, recursion) to create your fixed string. Eg:
function Combined_String (String_Collection : in String_Collection_Type) return String is
begin
if String_Collection'length = 1 then
return String_Collection(String_Collection'first);
end if;
return String_Collection(String_Collection'first) &
Combined_String (String_Collection'first + 1 .. String_Collection'last);
end Combined_String;
I don't know what type you used for Collection, so I'm making some guesses. In particular, I'm assuming its an unconstrained array of fixed strings. If it's not, you will need to replace some of the above code with whatever your container uses to return its bounds, access elements, and perform slicing.
From AdaPower.com:
function Next_Line(File : in Ada.Text_IO.File_Type :=
Ada.Text_Io.Standard_Input) return String is
Answer : String(1..256);
Last : Natural;
begin
Ada.Text_IO.Get_Line(File => File,
Item => Answer,
Last => Last);
if Last = Answer'Last then
return Answer & Next_Line(File);
else
return Answer(1..Last);
end if;
end Next_Line;
As you can see, this method builds a string (using Get_Line) of unlimited* length from the file it's reading from. So what you'll need to do, in order to keep what you have is something on the order of:
function Combined_String (String_Collection : in String_Collection_Type)
Return String is
begin
if String_Collection'length = 1 then
Return String_Collection(String_Collection'First).All;
end if;
Recursion:
Declare
Data : String:= String_Collection(String_Collection'First).All;
SubType Constraint is Positive Range
Positive'Succ(String_Collection'First)..String_Collection'Last;
Begin
Return Data & Combined_String( String_Collection(Constraint'Range) );
End Recursion;
end Combined_String;
Assuming that String_Collection is defined as:
Type String_Collection is Array (Positive Range <>) of Access String;
*Actually limited by Integer'Range, IIRC