46 lines
1.3 KiB
Ada
46 lines
1.3 KiB
Ada
with Ada.Text_IO;
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procedure Caesar is
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type modulo26 is modulo 26;
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function modulo26 (Character: Character; Output: Character) return modulo26 is
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begin
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return modulo26 (Character'Pos(Character)+Character'Pos(Output));
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end modulo26;
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function Character(Val: in modulo26; Output: Character)
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return Character is
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begin
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return Character'Val(Integer(Val)+Character'Pos(Output));
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end Character;
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function crypt (Playn: String; Key: modulo26) return String is
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Ciph: String(Playn'Range);
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begin
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for I in Playn'Range loop
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case Playn(I) is
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when 'A' .. 'Z' =>
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Ciph(I) := Character(modulo26(Playn(I)+Key), 'A');
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when 'a' .. 'z' =>
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Ciph(I) := Character(modulo26(Playn(I)+Key), 'a');
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when others =>
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Ciph(I) := Playn(I);
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end case;
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end loop;
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return Ciph;
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end crypt;
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Text: String := Ada.Text_IO.Get_Line;
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Key: modulo26 := 3; -- Default key from "Commentarii de Bello Gallico" shift cipher
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begin -- encryption main program
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Ada.Text_IO.Put_Line("Playn ------------>" & Text);
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Text := crypt(Text, Key);
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Ada.Text_IO.Put_Line("Ciphertext ----------->" & Text);
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Ada.Text_IO.Put_Line("Decrypted Ciphertext ->" & crypt(Text, -Key));
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end Caesar;
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