Constraint error overflow

Constraint error overflow

[Richard Iswara]

Ada beginner here. I was trying to multiply the first 100 integer and GNAT throw me a constraint error, overflow. I check the error was on integer 13. So what did I do wrong here?
Gnat CE 2020, Windows 10 Pro 64bit.
Here is the relevant program:

with Ada.Text_IO;
with Ada.Integer_Text_IO;

procedure Simple is
   sum : Natural := 0;
   mul : Natural := 1;

begin
   Ada.Text_IO.Put ( "Sum of first 100 integer is :" );
   Summing:
   for I in 1 .. 100 loop
      sum := sum + I;
   end loop Summing;
   Ada.Integer_Text_IO.Put ( sum );
   Ada.Text_IO.New_Line;

   Ada.Text_IO.Put ( "Multiple of the first 100 integer is :" );
   Ada.Text_IO.New_Line;
   Multiplying:
   for J in 1 .. 100 loop
      Ada.Integer_Text_IO.Put (J);
      Ada.Text_IO.New_Line;
      mul := mul * J;
   end loop Multiplying;
   Ada.Integer_Text_IO.Put ( mul );
   Ada.Text_IO.New_Line;
end Simple;

Re: Constraint error overflow

[Dmitry A. Kazakov]

On 2021-04-27 16:04, Richard Iswara wrote:
> Ada beginner here. I was trying to multiply the first 100 integer and GNAT throw me a constraint error, overflow. I check the error was on integer 13. So what did I do wrong here?

Nothing, it is just so that

    14! > 2**31 - 1

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de

Re: Constraint error overflow

[Richard Iswara]

On Tuesday, April 27, 2021 at 10:00:22 PM UTC+7, Dmitry A. Kazakov wrote:
> On 2021-04-27 16:04, Richard Iswara wrote: 
> > Ada beginner here. I was trying to multiply the first 100 integer and GNAT throw me a constraint error, overflow. I check the error was on integer 13. So what did I do wrong here?
> Nothing, it is just so that 
> 
> 14! > 2**31 - 1 
> 
> -- 
> Regards, 
> Dmitry A. Kazakov 
> http://www.dmitry-kazakov.de

So the compiler is restricted to 32 bit integer value. I had hoped for 64 bit to get 18 digits.
Thank you.

Re: Constraint error overflow

[Mark Lorenzen]

On Tuesday, April 27, 2021 at 5:32:20 PM UTC+2, haujek...@gmail.com wrote:
> So the compiler is restricted to 32 bit integer value. I had hoped for 64 bit to get 18 digits. 
> Thank you.

Define your own type instead of relying on pre-defined types. Ada is not C.

Regards,
Mark L

Re: Constraint error overflow

[Shark8]

On Tuesday, April 27, 2021 at 9:32:20 AM UTC-6, haujek wrote:
> So the compiler is restricted to 32 bit integer value. I had hoped for 64 bit to get 18 digits. 

Depends on the compiler.
You can always model your domain more explicitly:
Bit_Size : Constant := 64;
Bit_First : Constant := 0;
Bit_Last : Constant := 2**Big_Bit_Size - 1;
Type Big_Integer_Test is range Bit_First..Bit_Last with Size => Bit_Size;

Function Factorial(Input:Big_Integer_Test) return Big_Integer_Test is
(case Input is
  when 0 => 1,
  when 1 | 2 => Input,
  when others => Input * Factorial(Big_Integer_Test'Pred(Input))
);

Re: Constraint error overflow

[Jeffrey R. Carter]

On 4/27/21 5:32 PM, Richard Iswara wrote:
> 
> So the compiler is restricted to 32 bit integer value. I had hoped for 64 bit to get 18 digits.

No, the compiler defines type Integer as 32 bits. You can define other types 
with larger ranges. For trying to calculate 100!, even 64 bits is not enough; 
you'd need to use an unbounded integer package.

-- 
Jeff Carter
"There's no messiah here. There's a mess all right, but no messiah."
Monty Python's Life of Brian
84

Re: Constraint error overflow

[Dmitry A. Kazakov]

On 2021-04-27 17:32, Richard Iswara wrote:
> On Tuesday, April 27, 2021 at 10:00:22 PM UTC+7, Dmitry A. Kazakov wrote:
>> On 2021-04-27 16:04, Richard Iswara wrote:
>>> Ada beginner here. I was trying to multiply the first 100 integer and GNAT throw me a constraint error, overflow. I check the error was on integer 13. So what did I do wrong here?
>> Nothing, it is just so that
>>
>> 14! > 2**31 - 1

> So the compiler is restricted to 32 bit integer value. I had hoped for 64 bit to get 18 digits.

That won't give you 100! That is 158 digits or so.

Long_Float gamma function should do the trick, or arbitrary precision 
integer arithmetic.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de

Re: Constraint error overflow

[Simon Wright]

Richard Iswara <haujekchifan@gmail.com> writes:

> So the compiler is restricted to 32 bit integer value. I had hoped for
> 64 bit to get 18 digits.

GNAT comes with Long_Integer (64 bits).

Or yu could go with the Ada202x Big_Integers package
(http://www.ada-auth.org/standards/2xrm/html/RM-A-5-6.html),

pragma Ada_2020;

with Ada.Text_IO;
with Ada.Numerics.Big_Numbers.Big_Integers;

procedure Iswara is

   use Ada.Numerics.Big_Numbers.Big_Integers;

   Sum : Big_Natural := 0;
   Mul : Big_Natural := 1;

begin
   Ada.Text_IO.Put ( "Sum of the first 100 integers is :" );
   Ada.Text_IO.New_Line;
   Summing:
   for I in 1 .. 100 loop
      Sum := Sum + To_Big_Integer (I);
   end loop Summing;
   Ada.Text_IO.Put ( Sum'Image );
   Ada.Text_IO.New_Line;

   Ada.Text_IO.Put ( "Multiple of the first 100 integers is :" );
   Ada.Text_IO.New_Line;
   Multiplying:
   for J in 1 .. 100 loop
      Mul := Mul * To_Big_Integer (J);
   end loop Multiplying;
   Ada.Text_IO.Put ( Mul'Image );
   Ada.Text_IO.New_Line;
end Iswara;

which compiles fine with GNAT CE 2020 & FSF GCC 11.0.1; result

$ ./iswara 
Sum of the first 100 integers is :
 5050
Multiple of the first 100 integers is :
 93326215443944152681699238856266700490715968264381621468592963895217599993229915608941463976156518286253697920827223758251185210916864000000000000000000000000

Re: Constraint error overflow

[Richard Iswara]

On Tuesday, April 27, 2021 at 10:59:57 PM UTC+7, Dmitry A. Kazakov wrote:
> On 2021-04-27 17:32, Richard Iswara wrote: 
> > On Tuesday, April 27, 2021 at 10:00:22 PM UTC+7, Dmitry A. Kazakov wrote: 
> >> On 2021-04-27 16:04, Richard Iswara wrote: 
> >>> Ada beginner here. I was trying to multiply the first 100 integer and GNAT throw me a constraint error, overflow. I check the error was on integer 13. So what did I do wrong here? 
> >> Nothing, it is just so that 
> >> 
> >> 14! > 2**31 - 1
> > So the compiler is restricted to 32 bit integer value. I had hoped for 64 bit to get 18 digits.
> That won't give you 100! That is 158 digits or so. 
> 
> Long_Float gamma function should do the trick, or arbitrary precision 
> integer arithmetic.
> -- 
> Regards, 
> Dmitry A. Kazakov 
> http://www.dmitry-kazakov.de


Thank you all of you who responded and give very helpful advices. i am very much an amateur beginner in programming . .