Ada Programming, Algorithms, Chapter 1

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Chapter 1: Introduction

The following subprograms are implementations of the Inventing an Algorithm examples.

To Lower

The Ada example code does not append to the array as the algorithms. Instead we create an empty array of the desired length and then replace the characters inside.

File: to_lower_1.adb (view, plain text, download page, browse all)

function To_Lower (C : Character) return Character renames
Ada.Characters.Handling.To_Lower;

-- tolower - translates all alphabetic, uppercase characters
-- in str to lowercase
function To_Lower (Str : String) return String is
Result : String (Str'Range);
begin
for C in Str'Range loop
Result (C) := To_Lower (Str (C));
end loop;
return Result;
end To_Lower;

Would the append approach be impossible with Ada? No, but it would be significantly more complex and slower.

Equal Ignore Case

File: to_lower_2.adb (view, plain text, download page, browse all)

-- equal-ignore-case -- returns true if s or t are equal,
-- ignoring case
function Equal_Ignore_Case
(S  : String;
T  : String)
return Boolean
is
O : constant Integer := S'First - T'First;
begin
if T'Length /= S'Length then
return False; -- if they aren't the same length, they
-- aren't equal
else
for I in S'Range loop
if To_Lower (S (I)) /=
To_Lower (T (I + O))
then
return False;
end if;
end loop;
end if;
return True;
end Equal_Ignore_Case;

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