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sabomi's solution

to Roman Numerals in the PL/SQL Track

Published at Jul 13 2018 · 3 comments
Instructions
Test suite
Solution

Write a function to convert from normal numbers to Roman Numerals.

The Romans were a clever bunch. They conquered most of Europe and ruled it for hundreds of years. They invented concrete and straight roads and even bikinis. One thing they never discovered though was the number zero. This made writing and dating extensive histories of their exploits slightly more challenging, but the system of numbers they came up with is still in use today. For example the BBC uses Roman numerals to date their programmes.

The Romans wrote numbers using letters - I, V, X, L, C, D, M. (notice these letters have lots of straight lines and are hence easy to hack into stone tablets).

 1  => I
10  => X
 7  => VII

There is no need to be able to convert numbers larger than about 3000. (The Romans themselves didn't tend to go any higher)

Wikipedia says: Modern Roman numerals ... are written by expressing each digit separately starting with the left most digit and skipping any digit with a value of zero.

To see this in practice, consider the example of 1990.

In Roman numerals 1990 is MCMXC:

1000=M 900=CM 90=XC

2008 is written as MMVIII:

2000=MM 8=VIII

See also: http://www.novaroma.org/via_romana/numbers.html

Setup

Go through the setup instructions for PL/SQL to get ready to code:

http://exercism.io/languages/plsql

Running the Tests

Execute the tests by calling the run method in the respective ut_<exercise># package. The necessary code should be contained at the end of the test package. As an example, the test for the hamming exercise would be run using

begin
  ut_hamming#.run;
end;
/

Source

The Roman Numeral Kata http://codingdojo.org/cgi-bin/index.pl?KataRomanNumerals

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

ut_numeral#.plsql

create or replace package ut_numeral#
is
  procedure run;
end ut_numeral#;
/
 
create or replace package body ut_numeral#
is
  procedure test (
    i_descn                                       varchar2
   ,i_exp                                         varchar2
   ,i_act                                         varchar2
  )
  is
  begin
    if i_exp = i_act then
      dbms_output.put_line('SUCCESS: ' || i_descn);
    else
      dbms_output.put_line('FAILURE: ' || i_descn || ' - expected ' || nvl('' || i_exp, 'null') || ', but received ' || nvl('' || i_act, 'null'));
    end if;
  end test;
 
  procedure run
  is
  begin
    test(i_descn => 'test_1',    i_exp => 'I',      i_act => numeral#.to_roman(1   ));
    test(i_descn => 'test_2',    i_exp => 'II',     i_act => numeral#.to_roman(2   ));
    test(i_descn => 'test_3',    i_exp => 'III',    i_act => numeral#.to_roman(3   ));
    test(i_descn => 'test_4',    i_exp => 'IV',     i_act => numeral#.to_roman(4   ));
    test(i_descn => 'test_5',    i_exp => 'V',      i_act => numeral#.to_roman(5   ));
    test(i_descn => 'test_6',    i_exp => 'VI',     i_act => numeral#.to_roman(6   ));
    test(i_descn => 'test_9',    i_exp => 'IX',     i_act => numeral#.to_roman(9   ));
    test(i_descn => 'test_27',   i_exp => 'XXVII',  i_act => numeral#.to_roman(27  ));
    test(i_descn => 'test_48',   i_exp => 'XLVIII', i_act => numeral#.to_roman(48  ));
    test(i_descn => 'test_59',   i_exp => 'LIX',    i_act => numeral#.to_roman(59  ));
    test(i_descn => 'test_93',   i_exp => 'XCIII',  i_act => numeral#.to_roman(93  ));
    test(i_descn => 'test_141',  i_exp => 'CXLI',   i_act => numeral#.to_roman(141 ));
    test(i_descn => 'test_163',  i_exp => 'CLXIII', i_act => numeral#.to_roman(163 ));
    test(i_descn => 'test_402',  i_exp => 'CDII',   i_act => numeral#.to_roman(402 ));
    test(i_descn => 'test_575',  i_exp => 'DLXXV',  i_act => numeral#.to_roman(575 ));
    test(i_descn => 'test_911',  i_exp => 'CMXI',   i_act => numeral#.to_roman(911 ));
    test(i_descn => 'test_1024', i_exp => 'MXXIV',  i_act => numeral#.to_roman(1024));
    test(i_descn => 'test_3000', i_exp => 'MMM',    i_act => numeral#.to_roman(3000));
  end run;
end ut_numeral#;
/
 
begin
  ut_numeral#.run;
end;
/
create or replace package numeral#
is
  --+--------------------------------------------------------------------------+
  -- Convert from normal numbers to Roman Numerals
  --
  -- @param l_latin_number   the l_latin number as a string
  --
  -- @return                the Roman Numeral
  --+--------------------------------------------------------------------------+
  function to_roman (  
    l_latin_number                                 varchar2
  ) return varchar2;


  -- Exception: not convertable 
  exp_not_convertable                             exception;
end numeral#;
/

create or replace package body numeral#
is
  function to_roman (
    l_latin_number                                 varchar2
  ) return varchar2
  as
    l_roman                                      varchar2(25 char);
    l_latin                                      number := l_latin_number;
  begin  
     
     -- everything below 1 and > 3000 is unvalid
     if l_latin < 1 or l_latin > 3000 then raise exp_not_convertable; end if;
     
     -- just convert the numbers to letters
     while l_latin >= 1000 loop l_latin := l_latin - 1000; l_roman := l_roman || 'M';  end loop;     
     if    l_latin >= 500  then l_latin := l_latin - 500;  l_roman := l_roman || 'D'; end if;     
     while l_latin >= 100  loop l_latin := l_latin - 100;  l_roman := l_roman || 'C'; end loop;     
     if    l_latin >= 50   then l_latin := l_latin - 50;   l_roman := l_roman || 'L';  end if;
     while l_latin >= 10   loop l_latin := l_latin - 10;   l_roman := l_roman || 'X';  end loop;      
      if    l_latin >= 5   then l_latin := l_latin - 5;    l_roman := l_roman || 'V';  end if;     
     while l_latin >= 1    loop l_latin := l_latin - 1;    l_roman := l_roman || 'I'; end loop;
      
      -- implement the 'at most three letters' rule
      
      l_roman := replace(l_roman,'IIII','IV');
      l_roman := replace(l_roman,'XXXX','XL');
      l_roman := replace(l_roman,'CCCC','CD');
      
      -- implement the rule, that 'V', 'L', and 'D' at at most allowed once
      
      l_roman := replace(l_roman,'VIV','IX');
      l_roman := replace(l_roman,'LXL','XC');
      l_roman := replace(l_roman,'DCD','CM');
      
      return l_roman;

  exception 
     when exp_not_convertable
       then dbms_output.put_line('Expected an integer between 1 and 3000');
       raise;
     when others 
       then raise;
  end to_roman;

end numeral#;
/

Community comments

Find this solution interesting? Ask the author a question to learn more.
Avatar of chezwicker

So what do you think? More or less readable?

I like it!

Avatar of sabomi
sabomi
Solution Author
commented over 4 years ago

In cases like that it's really good! And the ">" instead of ">=" error of the second iteration would have been more obvious.

Avatar of sukarnar

This is good code and readable. Same steps can be recursive and could reduce the lines of code further. I have submitted a recursive solution to this problem.

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