Using multidimensional array in Ada - ada

Question

In this code, I need help writing a multidimensional array with a range between 2020-01-01 to 2119-12-31.
My code works but as you see there are no arrays in it. How can I write this code with only arrays?
with Ada.Text_IO; use Ada.Text_IO;
with Ada.Integer_Text_IO; use Ada.Integer_Text_IO;
Procedure Date is
type date_type is record
Str : string (1..8);
Length : Natural := 0; end record;
A: date_type;
begin
loop
Put ("Enter a date between 2020-01-01 to 2119-12-31 : ");
Get_Line (A.Str, A.Length);
exit when A.Length = 8;
Put_Line ("Wrong input. Try again.");
end loop;
Put_Line (A.Str (1 .. 4) & "-" & A.Str (5 .. 6) & "-" & A.Str (7 .. 8));
end Date;

Answer 1

Perhaps, rather than a multi-dimensional array you should consider using a record such as
type Year_Number is range 1900..3000;
type Month_Number is range 1..12;
type Day_Number is range 1..31;
type Date_Rec is record
Year : Year_Number;
Month : Month_Number;
Day : Day_Number;
end record;
subtype Year_String is string (1..4);
subtype Month_String is string (1..2);
subtype Day_String is string (1..2);
function To_Date (Yr : Year_String; Mnth : Month_String; Dy : Day_String)
return Date_Rec is
Result : Date_Rec;
begin
Result.Year := Year_Number'Value (Yr);
Result.Month := Month_Number'Value (Mnth);
Result.Day := Day_Number'Value (Dy);
return Result;
end To_Date;
You can now pass around instances of Date_
Rec doing whatever you want with the date.
If you go this far then you might want to consider using the Time type described in Ada Language Reference Manual sections 9.6 and 9.6.1.

Answer 2

You haven't asked a reasonable question here because "I want to use arrays" is not a good reason to use an array.
"This problem can be best solved with an array ... but how do I deal with ... ?" would be a reasonable question, but you haven't stated a problem,let alone one that needs an array.
This is important because "using an array" is thinking in the solution domain, like "using a chisel". It's not the way to think about programming in Ada, (or IMO in any language).
Try thinking in the problem domain first : instead of "I want to use a chisel", I think "I want to recess this hinge so the door fits precisely" and a chisel is the neatest way of doing the job.
Then "How can I best validate a date?" would be one reasonable question, or "how can I store events that happen on each day for 100 years?"
The answer to the first question is probably in the Ada.Calendar package. Possibly the Value function in Ada.Calendar.Formatting, with an exception handler to catch incomprehensible strings and make the user try again.
with Ada.Text_IO; use Ada.Text_IO;
with Ada.Calendar;
with Ada.Calendar.Formatting;
procedure date is
Date : Ada.Calendar.Time;
Done : Boolean;
begin
loop
Put ("Enter a date between 2020-01-01 to 2119-12-31 : ");
Done := TRUE;
declare
A : String := Get_Line & " 12:00:00";
begin
Date := Ada.Calendar.Formatting.Value(A); -- validate it's a date
Done := Ada.Calendar.Year(Date) >= 2020
and Ada.Calendar.Year(Date) < 2120; -- validate correct range
exception
when Constraint_Error => Done := False; -- Formatting.Value failed
end;
exit when Done;
Put("Try Again : ");
end loop;
end date;
The answer to the second is probably a 1-dimensional array indexed by Day_Count from Ada.Calendar.Arithmetic but let's use the wrong tool : a 3D array indexed by your range of years, Month_Number and Day_Number from the Ada.Calendar base package.
with Ada.Text_IO; use Ada.Text_IO;
with Ada.Calendar; use Ada.Calendar;
with Ada.Calendar.Formatting;
with Ada.Strings.Unbounded; use Ada.Strings.Unbounded;
procedure date is
Date : Ada.Calendar.Time;
Done : Boolean := TRUE;
Event_Array : array(2020 .. 2119,
Ada.Calendar.Month_Number,
Ada.Calendar.Day_Number) of Unbounded_String;
begin
Event_Array := (others => (others => (others => Null_Unbounded_String)));
Event_Array(2020,11,3) := To_Unbounded_String("nothing much");
loop
Put ("Enter a date between 2020-01-01 to 2119-12-31 : ");
Done := TRUE;
declare
A : String := Get_Line & " 12:00:00";
begin
Date := Ada.Calendar.Formatting.Value(A);
Done := Ada.Calendar.Year(Date) >= 2020
and Ada.Calendar.Year(Date) < 2120;
exception
when Constraint_Error => Done := False;
end;
exit when Done;
Put("Try Again : ");
end loop;
Put_Line("Today " & Ada.Calendar.Formatting.Image(Date) & " : " &
To_String(Event_Array(Year(Date), Month(Date), Day(Date))) & " happened");
end date;
Test with the string 2020-11-03