Ada Programming/Mathematical calculations - eMyTextBooks

Ada Programming/Mathematical calculations

Ada is very well suited for all kind of calculations. You can define you own fixed point and floting point types and - with the aid of generic packages call all the mathematical functions you need. I that respect Ada is on par with Fortran. This module will show you how to use them and while we progress we create a simple RPN calculator.

Simple calculations

Addition

Additions can be done using the predefined operator +. The operator is predefined for all numeric types and the following, working code, demonstrates its use:

-- The Package Text_IO (http://www.adaic.org/standards/95lrm/html/RM-A-10-1.html)
with Ada.Text_IO;

procedure Numeric_1 is
   type Value_Type is digits 12
         range -999_999_999_999.0e999 .. 999_999_999_999.0e999;

   package T_IO renames Ada.Text_IO;
   package F_IO is new  Ada.Text_IO.Float_IO (Value_Type);

   Value_1 : Value_Type;
   Value_2 : Value_Type;

begin
   T_IO.Put ("First Value : ");
   F_IO.Get (Value_1);
   T_IO.Put ("Second Value : ");
   F_IO.Get (Value_2);

   F_IO.Put (Value_1);
   T_IO.Put (" + ");
   F_IO.Put (Value_2);
   T_IO.Put (" = ");
   F_IO.Put (Value_1 + Value_2);
end Numeric_1;

Subtraction

Subtractions can be done using the predefined operator -. The following extended demo shows the use of + and - operator together:

-- The Package Text_IO (http://www.adaic.org/standards/95lrm/html/RM-A-10-1.html)
with Ada.Text_IO;

procedure Numeric_2
is
  type Value_Type
  is digits
     12
  range
     -999_999_999_999.0e999 .. 999_999_999_999.0e999;

  package T_IO renames Ada.Text_IO;
  package F_IO is new  Ada.Text_IO.Float_IO (Value_Type);

  Value_1   : Value_Type;
  Value_2   : Value_Type;
  Result    : Value_Type;
  Operation : Character;

begin
  T_IO.Put ("First Value  : ");
  F_IO.Get (Value_1);
  T_IO.Put ("Second Value : ");
  F_IO.Get (Value_2);
  T_IO.Put ("Operation    : ");
  T_IO.Get (Operation);

  case Operation is
     when '+' =>
        Result := Value_1 + Value_2;
     when '-' =>
        Result := Value_1 - Value_2;
     when others =>
        T_IO.Put_Line ("Illegal Operation.");
        goto Exit_Numeric_2;
  end case;

  F_IO.Put (Value_1);
  T_IO.Put (" ");
  T_IO.Put (Operation);
  T_IO.Put (" ");
  F_IO.Put (Value_2);
  T_IO.Put (" = ");
  F_IO.Put (Result);

<<Exit_Numeric_2>>
  return;

end Numeric_2;

Purists might be surprised about the use of goto - but some people prefer the use of goto over the use of multiple return statements if inside functions - given that, the opinions on this topic vary strongly. See the isn't goto evil article.

Multiplication

Multiplicationcan be done using the predefined operator *. For a demo see the next chapter about Division.

Division

Divisions can be done using the predefined operators /, mod, rem. The operator / performes a normal division, mod returns a modulus division and rem returns the remainder of the modulus division.

The following extended demo shows the use of the +, -, * and / operators together as well as the use of an four number wide stack to store intermediate results:

The operators mod and rem are not part of the demonstration as they are only defined for integer types.

with Ada.Text_IO;

procedure Numeric_3 is
   procedure Pop_Value;
   procedure Push_Value;

   type Value_Type is digits 12 range
     -999_999_999_999.0e999 .. 999_999_999_999.0e999;

   type Value_Array is array (Natural range 1 .. 4) of Value_Type;

   package T_IO renames Ada.Text_IO;
   package F_IO is new Ada.Text_IO.Float_IO (Value_Type);

   Values    : Value_Array := (others => 0.0);
   Operation : String (1 .. 40);
   Last      : Natural;

   procedure Pop_Value is
   begin
      Values (Values'First + 1 .. Values'Last) :=
        Values (Values'First + 2 .. Values'Last) & 0.0;
   end Pop_Value;

   procedure Push_Value is
   begin
      Values (Values'First + 1 .. Values'Last) :=
        Values (Values'First .. Values'Last - 1);
   end Push_Value;

begin
   Main_Loop:
   loop
      T_IO.Put (">");
      T_IO.Get_Line (Operation, Last);

      if Last = 1 and then Operation (1) = '+' then
         Values (1) := Values (1) + Values (2);
         Pop_Value;
      elsif Last = 1 and then Operation (1) = '-' then
         Values (1) := Values (1) + Values (2);
         Pop_Value;
      elsif Last = 1 and then Operation (1) = '*' then
         Values (1) := Values (1) * Values (2);
         Pop_Value;
      elsif Last = 1 and then Operation (1) = '/' then
         Values (1) := Values (1) / Values (2);
         Pop_Value;
      elsif Last = 4 and then Operation (1 .. 4) = "exit" then
         exit Main_Loop;
      else
         Push_Value;
         F_IO.Get (From => Operation, Item => Values (1), Last => Last);
      end if;
      
      Display_Loop:
      for I in reverse Value_Array'Range loop
         F_IO.Put
           (Item => Values (I),
            Fore => F_IO.Default_Fore,
            Aft  => F_IO.Default_Aft,
            Exp  => 4);
         T_IO.New_Line;
      end loop Display_Loop;
   end loop Main_Loop;

   return;
end Numeric_3;

Exponential calculations

All exponential functions are defined inside the generic package Ada.Numerics.Generic_Elementary_Functions.

Power of

Calculation of the form x^y are performed by the operator **. Beware: There are two versions of this operator. The predefined operator ** allows only for Standart.Integer to be used as exponent. If you need to use a floating point type as exponent you need to use the ** defined in Ada.Numerics.Generic_Elementary_Functions.

Root

The square root is calculated with the function Sqrt(). There is no function defined to calculate an abritary root . However you can use logarithms to calculate an arbitrary root using the mathematical identity: which will become root := Exp (Log (a) / b)<code> in Ada. Alternatively, use which, in Ada, is <code>root := a**(1/b).

Logarithm

Ada.Numerics.Generic_Elementary_Functions defines a function for both the arbritary logarithm log_n(x) and the natural logaritm log_e(x) both of of which have the same name Log() distinquished by the amount of parameters.

Demonstration

The following extended demo shows the how to use the exponential functions in Ada. The new demo also uses Unbounded_String instead of Strings which make the comparisons easier.

Please note that from now on we won't copy the full sources any more. Do follow the download links to see the full programm.

with Ada.Text_IO;
with Ada.Numerics.Generic_Elementary_Functions;
with Ada.Strings.Unbounded;

procedure Numeric_4 is
  package Str renames Ada.Strings.Unbounded;
  package T_IO renames Ada.Text_IO;

  procedure Pop_Value;
  procedure Push_Value;
  function Get_Line return Str.Unbounded_String;

  type Value_Type is digits 12 range
     -999_999_999_999.0e999 .. 999_999_999_999.0e999;

  type Value_Array is array (Natural range 1 .. 4) of Value_Type;

  package F_IO is new Ada.Text_IO.Float_IO (Value_Type);
  package Value_Functions is new Ada.Numerics.Generic_Elementary_Functions (
     Value_Type);

  use Value_Functions;
  use type Str.Unbounded_String;

  Values    : Value_Array := (others => 0.0);
  Operation : Str.Unbounded_String;
  Dummy     : Natural;

  function Get_Line return Str.Unbounded_String is
     BufferSize : constant := 2000;
     Retval     : Str.Unbounded_String := Str.Null_Unbounded_String;
     Item       : String (1 .. BufferSize);
     Last       : Natural;
  begin
     Get_Whole_Line :
        loop
           T_IO.Get_Line (Item => Item, Last => Last);

           Str.Append (Source => Retval, New_Item => Item (1 .. Last));

           exit Get_Whole_Line when Last < Item'Last;
        end loop Get_Whole_Line;

     return Retval;
  end Get_Line;

...

begin
  Main_Loop :
     loop
        T_IO.Put (">");
        Operation := Get_Line;

...
        elsif Operation = "e" then
           --  insert e
           Push_Value;
           Values (1) := Ada.Numerics.e;
        elsif Operation = "**" or else Operation = "^" then
           --  power of x^y
           Values (1) := Values (1) ** Values (2);
           Pop_Value;
        elsif Operation = "sqr" then
           --  square root
           Values (1) := Sqrt (Values (1));
        elsif Operation = "root" then
           --  arbritary root
           Values (1) :=
              Exp (Log (Values (2)) / Values (1));
           Pop_Value;
        elsif Operation = "ln" then
           --  natural logarithm
           Values (1) := Log (Values (1));
        elsif Operation = "log" then
           --  based logarithm
           Values (1) :=
              Log (Base => Values (1), X => Values (2));
           Pop_Value;
        elsif Operation = "exit" then
           exit Main_Loop;
        else
           Push_Value;
           F_IO.Get
             (From => Str.To_String (Operation),
              Item => Values (1),
              Last => Dummy);
        end if;

...
     end loop Main_Loop;

  return;
end Numeric_4;

Higher math

Trigonometric calculations

The full set of trigonometric functions are defined inside the generic package Ada.Numerics.Generic_Elementary_Functions. All functions are defined for 2π and an arbirtary cycle value (a full cycle of revolution).

Please note the difference of calling the Arctan () function.

with Ada.Text_IO;
with Ada.Numerics.Generic_Elementary_Functions;
with Ada.Strings.Unbounded;

procedure Numeric_5 is

...

  procedure Put_Line (Value : in Value_Type);

  use Value_Functions;
  use type Str.Unbounded_String;

  Values    : Value_Array := (others => 0.0);
  Cycle     : Value_Type  := Ada.Numerics.Pi;
  Operation : Str.Unbounded_String;
  Dummy     : Natural;

...

  procedure Put_Line (Value : in Value_Type) is
  begin
     if abs Value_Type'Exponent (Value) >=
        abs Value_Type'Exponent (10.0 ** F_IO.Default_Aft)
     then
        F_IO.Put
          (Item => Value,
           Fore => F_IO.Default_Aft,
           Aft  => F_IO.Default_Aft,
           Exp  => 4);
     else
        F_IO.Put
          (Item => Value,
           Fore => F_IO.Default_Aft,
           Aft  => F_IO.Default_Aft,
           Exp  => 0);
     end if;
     T_IO.New_Line;

     return;
  end Put_Line;

...

begin
  Main_Loop :
     loop
        Display_Loop :
           for I in reverse  Value_Array'Range loop
              Put_Line (Values (I));
           end loop Display_Loop;
        T_IO.Put (">");
        Operation := Get_Line;

...
        elsif Operation = "deg" then
           --  switch to degrees
           Cycle := 360.0;
        elsif Operation = "rad" then
           --  switch to degrees
           Cycle := Ada.Numerics.Pi;
        elsif Operation = "grad" then
           --  switch to degrees
           Cycle := 400.0;
        elsif Operation = "pi" or else Operation = "π" then
           --  switch to degrees
           Push_Value;
           Values (1) := Ada.Numerics.Pi;
        elsif Operation = "sin" then
           --  sinus
           Values (1) := Sin (X => Values (1), Cycle => Cycle);
        elsif Operation = "cos" then
           --  cosinus
           Values (1) := Cot (X => Values (1), Cycle => Cycle);
        elsif Operation = "tan" then
           --  tangents
           Values (1) := Tan (X => Values (1), Cycle => Cycle);
        elsif Operation = "cot" then
           --  cotanents
           Values (1) := Cot (X => Values (1), Cycle => Cycle);
        elsif Operation = "asin" then
           --  arc-sinus
           Values (1) := Arcsin (X => Values (1), Cycle => Cycle);
        elsif Operation = "acos" then
           --  arc-cosinus
           Values (1) := Arccos (X => Values (1), Cycle => Cycle);
        elsif Operation = "atan" then
           --  arc-tangents
           Values (1) := Arctan (Y => Values (1), Cycle => Cycle);
        elsif Operation = "acot" then
           --  arc-cotanents
           Values (1) := Arccot (X => Values (1), Cycle => Cycle);

...
     end loop Main_Loop;

  return;
end Numeric_5;

The Demo also contains an improved numeric output which behaves more like a normal calculator.

Hyperbolic calculations

You guessed it: The full set of hyperbolic functions is defined inside the generic package Ada.Numerics.Generic_Elementary_Functions.

with Ada.Text_IO;
with Ada.Numerics.Generic_Elementary_Functions;
with Ada.Strings.Unbounded;
with Ada.Exceptions;

procedure Numeric_6 is
  package Str renames Ada.Strings.Unbounded;
  package T_IO renames Ada.Text_IO;
  package Exept renames Ada.Exceptions;

...

 begin
  Main_Loop :
     loop
        Try :
           begin
              Display_Loop :
...
              elsif Operation = "sinh" then
                 --  sinus hyperbolic
                 Values (1) := Sinh (Values (1));
              elsif Operation = "cosh" then
                 --  cosinus hyperbolic
                 Values (1) := Coth (Values (1));
              elsif Operation = "tanh" then
                 --  tangents hyperbolic
                 Values (1) := Tanh (Values (1));
              elsif Operation = "coth" then
                 --  cotanents hyperbolic
                 Values (1) := Coth (Values (1));
              elsif Operation = "asinh" then
                 --  arc-sinus hyperbolic
                 Values (1) := Arcsinh (Values (1));
              elsif Operation = "acosh" then
                 --  arc-cosinus hyperbolic
                 Values (1) := Arccosh (Values (1));
              elsif Operation = "atanh" then
                 --  arc-tangents hyperbolic
                 Values (1) := Arctanh (Values (1));
              elsif Operation = "acoth" then
                 --  arc-cotanents hyperbolic
                 Values (1) := Arccoth (Values (1));
...
           exception
              when An_Exception : others =>
                 T_IO.Put_Line
                   (Exept.Exception_Information (An_Exception));
           end Try;
     end loop Main_Loop;

  return;
end Numeric_6;

As added bonus this version supports error handling and therefore won't just crash when an illegal calculation is performed.

Complex arithmethic

For complex arithmethic Ada provides the package Ada.Numerics.Generic_Complex_Types. This package is part of the "special need Annexes" which means it is optional. The open source Ada compiler GNAT implements all "special need Annexes" and therefore has complex arithmethic available.

Since Ada support user defined operators all (+, -, *) operators have there usual meaning as soon as the package Ada.Numerics.Generic_Complex_Types has been instanciated (package ... is new ...) and the type has been made visible (use type ...)

Ada also provides the packages Ada.Text_IO.Complex_IO and Ada.Numerics.Generic_Complex_Elementary_Functions which provide similar functionality to there normal counterparts. But there are some differences:

• Ada.Numerics.Generic_Complex_Elementary_Functions supports only the exponential and trigonometric functions which make sense in complex arithmethic.

• Ada.Text_IO.Complex_IO is a child package of Ada.Text_IO and therefore needs it's own with. Note: the Ada.Text_IO.Complex_IOGet ()<code> function is pretty fault tolerant - if you forget the "," or the "()" pair it will still parse the input correctly.

with Ada.Text_IO.Complex_IO;
with Ada.Numerics.Generic_Complex_Types;
with Ada.Numerics.Generic_Complex_Elementary_Functions;
with Ada.Strings.Unbounded;
with Ada.Exceptions; 

procedure Numeric_7 is

...
 
  package Complex_Types is new Ada.Numerics.Generic_Complex_Types (
     Value_Type);
  package Complex_Functions is new
     Ada.Numerics.Generic_Complex_Elementary_Functions (
     Complex_Types);
  package C_IO is new Ada.Text_IO.Complex_IO (Complex_Types);

  type Value_Array is
     array (Natural range 1 .. 4) of Complex_Types.Complex;

  procedure Put_Line (Value : in Complex_Types.Complex);

  use type Complex_Types.Complex;
  use type Str.Unbounded_String;
  use Complex_Functions;

  Values    : Value_Array :=
     (others => Complex_Types.Complex'(Re => 0.0, Im => 0.0));

...
 
  procedure Put_Line (Value : in Complex_Types.Complex) is
  begin
     if (abs Value_Type'Exponent (Value.Re) >=
         abs Value_Type'Exponent (10.0 ** C_IO.Default_Aft))
       or else (abs Value_Type'Exponent (Value.Im) >=
                abs Value_Type'Exponent (10.0 ** C_IO.Default_Aft))
     then
        C_IO.Put
          (Item => Value,
           Fore => C_IO.Default_Aft,
           Aft  => C_IO.Default_Aft,
           Exp  => 4);
     else
        C_IO.Put
          (Item => Value,
           Fore => C_IO.Default_Aft,
           Aft  => C_IO.Default_Aft,
           Exp  => 0);
     end if;
     T_IO.New_Line;

     return;
  end Put_Line;

begin

...
              elsif Operation = "e" then
                 --  insert e
                 Push_Value;
                 Values (1) :=
                    Complex_Types.Complex'(Re => Ada.Numerics.e, Im => 0.0);

...

              elsif Operation = "pi" or else Operation = "π" then
                 --  insert pi
                 Push_Value;
                 Values (1) :=
                    Complex_Types.Complex'(Re => Ada.Numerics.Pi, Im => 0.0);
              elsif Operation = "sin" then
                 --  sinus
                 Values (1) := Sin (Values (1));
              elsif Operation = "cos" then
                 --  cosinus
                 Values (1) := Cot (Values (1));
              elsif Operation = "tan" then
                 --  tangents
                 Values (1) := Tan (Values (1));
              elsif Operation = "cot" then
                 --  cotanents
                 Values (1) := Cot (Values (1));
              elsif Operation = "asin" then
                 --  arc-sinus
                 Values (1) := Arcsin (Values (1));
              elsif Operation = "acos" then
                 --  arc-cosinus
                 Values (1) := Arccos (Values (1));
              elsif Operation = "atan" then
                 --  arc-tangents
                 Values (1) := Arctan (Values (1));
              elsif Operation = "acot" then
                 --  arc-cotanents
                 Values (1) := Arccot (Values (1));

...

  return;
end Numeric_7;