28{
33 typedef typename compositor_t::function function_t;
34
36
37 symbol_table_t symbol_table;
38
39 symbol_table.add_function("println", println);
40 symbol_table.add_constants();
41
42 compositor_t compositor(symbol_table);
43
44 compositor.add(
45 function_t("archimedes_pi")
46 .var("iterations")
47 .expression
48 (
49 " var s := 1.0; "
50 " var approx_pi := 0.0; "
51 " "
52 " for (var i := 0; i < iterations; i += 1) "
53 " { "
54 " var n := 6 * 2^i; "
55 " var s2 := (s / 2)^2; "
56 " var t := sqrt(1 - s2); "
57 " var q := 1 - t; "
58 " var p := n * s; "
59 " "
60 " approx_pi := p / 2; "
61 " s := sqrt(q^2 + s2); "
62 " }; "
63 " "
64 " approx_pi; "
65 ));
66
67 const std::string archimedes_pi_program =
68 " const var n := 30; "
69 " "
70 " for (var i := 1; i <= n; i += 1) "
71 " { "
72 " var approx_pi := archimedes_pi(i); "
73 " var abs_error := abs(approx_pi - pi); "
74 " "
75 " println('approx pi: ', approx_pi, ' abs error:', abs_error); "
76 " } ";
77
78 expression_t expression;
79 expression.register_symbol_table(symbol_table);
80
81 parser_t parser;
82 parser.compile(archimedes_pi_program,expression);
83
84 expression.value();
85}
