Aminet 37/Aminet 37 (2000)(Schatztruhe)[!][Jun 2000].iso/Aminet/dev/lang/sofa.lha/sofa/smalleiffel/lib_number/number_tools.e

Text File | 2000-03-25 | 5KB | 236 lines

-- This file is  free  software, which  comes  along  with  SmallEiffel. This
-- software  is  distributed  in the hope that it will be useful, but WITHOUT
-- ANY  WARRANTY;  without  even  the  implied warranty of MERCHANTABILITY or
-- FITNESS  FOR A PARTICULAR PURPOSE. You can modify it as you want, provided
-- this header is kept unaltered, and a notification of the changes is added.
-- You  are  allowed  to  redistribute  it and sell it, alone or as a part of
-- another product.
--          Copyright (C) 1994-98 LORIA - UHP - CRIN - INRIA - FRANCE
--            Dominique COLNET and Suzanne COLLIN - [e-mail]
--                       http://SmallEiffel.loria.fr
--
expanded class NUMBER_TOOLS
--
-- This clas provides abstract creation functions for NUMBERs.
--
-- One may inherit this class in order to use NUMBERs.
--

feature

   is_number(s: STRING): BOOLEAN is
     -- Is `s' the view of some NUMBER ?
      require
     not s.is_empty
      local
     i, state: INTEGER;
     c: CHARACTER;
      do
     from
        i := 1;
        c := s.item(i);
     until
        state > 6 or else i > s.count
     loop
        inspect
           state
        when 0 then
           -- Waiting optional sign or first digit :
           inspect
          c
           when ' ', '%T' then
           when '+', '-' then
          state := 1;
           when '0' .. '9' then
          state := 2;
           else
          state := 8;
           end;
        when 1 then
                -- Waiting first digit (sign read) :
           inspect
          c
           when ' ', '%T' then
           when '0' .. '9' then
          state := 2;
           else
          state := 8;
           end;
        when 2 then
           -- Inside integer or numerator :
           inspect
          c
           when ' ', '%T' then
          state := 3;
           when '0' .. '9' then
           when '/' then
          state := 4;
           else
          state := 8;
           end;
        when 3 then
           -- Waiting end of integer or / of fraction :
           inspect
          c
           when ' ', '%T' then
           when '/' then
          state := 4;
           else
          state := 8;
           end;
        when 4 then
           -- Inside a fraction after / :
           inspect
          c
           when ' ', '%T' then
           when '0' .. '9' then
          state := 5;
           else
          state := 8;
           end;
        when 5 then
           -- Inside denominator :
           inspect
          c
           when ' ', '%T' then
          state := 6;
           when '0' .. '9' then
           else
          state := 8;
           end;
        when 6 then
           -- After denominator :
           inspect
          c
           when ' ', '%T' then
           else
          state := 8;
           end;
        end;
        -- state = 7 : end.
        -- state = 8 : error.
        i := i + 1;
        if i <= s.count then
           c := s.item(i);
        end;
     end;
     -- Setting `Result' :
     inspect
        state
     when 2, 3, 5, 6, 7 then
        Result := true;
     else
     end;
      end;


   from_integer(n: INTEGER): NUMBER is
     -- Uses value `n' to create a new NUMBER.
      do
     if (n = Minimum_integer)  then
        !LARGE_NEGATIVE_INTEGER!Result.make_smaller(0);
         else
        !SMALL_INTEGER!Result.make(n);
     end;
      ensure
     Result.to_integer = n
      end;

   from_string(s: STRING): NUMBER is
     -- Uses contents of `s' to create a new NUMBER.
      require
     is_number(s)
      local
     i: INTEGER;
     num, den: ABSTRACT_INTEGER;
     nb_is_negative: BOOLEAN;
     length, first, last, base: INTEGER;
     power: ABSTRACT_INTEGER;
      do
     i := s.index_of('/');
     if (i = s.count + 1) then
        nb_is_negative := false;
        if s.first.is_equal('-') then
           nb_is_negative := true;
           s.remove_first(1);
        elseif s.first.is_equal('+') then
           s.remove_first(1);
        end;
        from
           length := i.Maximum_integer.to_string.count - 1;
           !SMALL_INTEGER!Result.make(0);
           last := s.count;
           power ?= Result.one;
           check
          power /= Void;
           end;
           base := 10^length;
        until
           last <= 0
        loop
           first := last - length;
           if first < 0 then
          first := 0;
           end;
           Result := Result + ( power @* s.substring(first+1, last).to_integer );
           power ?= power @* base;
           check
          power /= Void;
           end;
           last := first;
        end;
        if nb_is_negative then
           Result := -Result;
        end;
     else
        num ?= from_string( s.substring(1, i - 1) );
        den ?= from_string( s.substring(i +1, s.count ) );
        check
           num /= Void;
           den /= Void;
        end;
        if (num \\ den).same_as( num.zero ) then
           Result := num / den;
        else
           if num.is_integer and then den.is_integer then
          !SMALL_FRACTION!Result.make_from_integer(num.to_integer, den.to_integer);
           else
          nb_is_negative := num.is_negative xor den.is_negative;
          num ?= num.abs;
          den ?= den.abs;
          check
             num /= Void;
             den /= Void;
          end;
          !LARGE_FRACTION!Result.make(num, den, nb_is_negative);
           end;
        end;
     end;
      ensure
     Result /= Void
      end;

   from_input_stream(input: INPUT_STREAM ): NUMBER is
     -- Create a number from a file or standard input
      require
     input.is_connected
      local
     string: STRING;
      do
     if not( input.end_of_input ) then
        !!string.make(0);
        input.read_line_in( string );
        Result := from_string( string );
     end;
      end;

end -- NUMBER_TOOLS