/tutorial/number/example5.e

 1class EXAMPLE5
 2   --
 3   -- Using the NUMBER_TOOLS parser.
 4   --
 5
 6create {ANY}
 7   make
 8
 9feature {}
10   make
11      local
12         stop: BOOLEAN; formula: STRING
13      do
14         from
15         until
16            stop
17         loop
18            io.put_string(once "[
19                Type Q to quit or ...
20                Enter your NUMBER formula on a single line:
21
22                      ]")
23            io.read_line
24            formula := io.last_string.twin
25            if formula.is_empty then
26               stop := True
27            else
28               if formula.count = 1 then
29                  inspect
30                     formula.first
31                  when 'Q', 'q' then
32                     stop := True
33                  else
34                  end
35               end
36               if not stop then
37                  parsing_of(formula)
38               end
39            end
40         end
41         io.put_string("Bye.%N")
42      end
43
44   parsing_of (formula: STRING)
45      local
46         number_tools: NUMBER_TOOLS; number: NUMBER; i: INTEGER
47      do
48         if number_tools.is_number(formula) then
49            number := number_tools.from_string(formula)
50            if number /= Void then
51               io.put_string(once "=%N")
52               io.put_number(number)
53               if number.is_fraction_general_number and then number.fit_real then
54                  io.put_string(once " (")
55                  io.put_real(number.force_to_real_64)
56                  io.put_character(')')
57               end
58               io.put_new_line
59            else
60               io.put_string(once "Error: ")
61               print_error(number_tools.parser_buffer.last_error)
62            end
63         else
64            io.put_string(once "Syntax error: ")
65            print_error(number_tools.parser_buffer.last_error)
66            io.put_line(formula)
67            from
68               i := 1
69            until
70               i = number_tools.parser_buffer.current_index
71            loop
72               io.put_character(' ')
73               i := i + 1
74            end
75
76            io.put_string(once "^%N")
77         end
78      end
79
80   print_error (error: PARSE_ERROR)
81      require
82         error /= Void
83      local
84         err: PARSE_ERROR
85      do
86         from
87            err := error
88         until
89            err = Void
90         loop
91            io.put_line(err.message)
92            err := err.next
93         end
94      end
95
96end -- class EXAMPLE5