Arrays Example

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--  letters.ada - count lower-case letters read from user
--
--  written by: Lawrie Brown / 29 Jul 94
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with TEXT_IO;

procedure lc_letter_freq is

    package int_io is new TEXT_IO.INTEGER_IO (INTEGER);
    use TEXT_IO, int_io;

    subtype lc_letters is CHARACTER range 'a' .. 'z';
    type freq_table is array (lc_letters) of INTEGER;

    count : freq_table := (others => 0); -- freq counts
    char  : CHARACTER;                   -- letter just read

begin -- lc_letter_freq 
    -- give some instructions
    PUT_LINE ("This program will count lc letters");
    PUT_LINE ("Enter lines of text, finish with '.'");

    -- get some characters from the user
    loop
        GET(char);
        exit when char = '.';
        if char in lc_letters then
            count(char) := count(char) + 1;
        end if;
    end loop;

    -- now show how many letters were read
    NEW_LINE;
    PUT_LINE("Letter  Freq");
    NEW_LINE;

    for t in lc_letters loop
        PUT(t); PUT(count(t), width=>11); NEW_LINE;
    end loop;

end lc_letter_freq;