parser/operator.cpp

   1 #include <ail/file.hpp>
   2 #include <ail/string.hpp>
   3 #include <fridh/parser.hpp>
   4 #include <fridh/lexer.hpp>
   5
   6 namespace fridh
   7 {
   8         void call_check(std::size_t extremum_offset)
   9         {
  10                 if(extremum_offset != 1)
  11                         throw ail::exception("Invalid call offset encountered during operator resolution");
  12         }
  13
  14         void visualise_parse_tree_nodes(parse_tree_nodes & input)
  15         {
  16                 for(std::size_t i = 0; i < input.size(); i++)
  17                         std::cout << (i + 1) << ". " << input[i].to_string() << std::endl;
  18         }
  19
  20         void parser::operator_resolution(parse_tree_nodes & input, parse_tree_node & output)
  21         {
  22                 if(input.size() == 1)
  23                 {
  24                         output = input[0];
  25                         return;
  26                 }
  27
  28                 bool got_an_operator = false;
  29                 word extremum;
  30                 std::size_t extremum_offset;
  31
  32                 for(std::size_t i = 0, end = input.size(); i < end; i++)
  33                 {
  34                         parse_tree_node & current_node = input[i];
  35                         word precedence;
  36
  37                         bool is_initialised_unary_node =
  38                                 current_node.type == parse_tree_node_type::unary_operator_node &&
  39                                 current_node.unary_operator_pointer->argument.type != parse_tree_node_type::uninitialised
  40                         ;
  41
  42                         bool is_initialised_call_node =
  43                                 current_node.type == parse_tree_node_type::call &&
  44                                 i == 0;
  45
  46                         if
  47                         (
  48                                 is_initialised_unary_node ||
  49                                 is_initialised_call_node
  50                         )
  51                                 continue;
  52
  53                         try
  54                         {
  55                                 if(get_parse_tree_node_precedence(current_node, precedence))
  56                                 {
  57                                         if
  58                                         (
  59                                                 !got_an_operator ||
  60                                                 precedence > extremum ||
  61                                                 (is_right_to_left_operator(current_node) && precedence == extremum)
  62                                         )
  63                                         {
  64                                                 got_an_operator = true;
  65                                                 extremum = precedence;
  66                                                 extremum_offset = i;
  67                                         }
  68                                 }
  69                         }
  70                         catch(ail::exception & exception)
  71                         {
  72                                 error(exception.get_message());
  73                         }
  74                 }
  75
  76                 if(!got_an_operator)
  77                         error("Failed to perform operator resolution");
  78
  79                 parse_tree_node & operator_node = input[extremum_offset];
  80                 std::size_t next_offset = extremum_offset + 1;
  81                 switch(operator_node.type)
  82                 {
  83                         case parse_tree_node_type::unary_operator_node:
  84                         {
  85                                 std::size_t argument_offset;
  86                                 if(operator_node.is_post_fix())
  87                                         argument_offset = extremum_offset - 1;
  88                                 else
  89                                         argument_offset = next_offset;
  90
  91                                 if(argument_offset >= input.size())
  92                                         error("Missing operator for unary argument");
  93
  94                                 parse_tree_unary_operator_node & unary_operator_node = *operator_node.unary_operator_pointer;
  95                                 unary_operator_node.argument = input[argument_offset];
  96                                 input.erase(input.begin() + argument_offset);
  97                                 break;
  98                         }
  99
 100                         case parse_tree_node_type::binary_operator_node:
 101                         {
 102                                 parse_tree_binary_operator_node & binary_operator_node = *operator_node.binary_operator_pointer;
 103
 104                                 if(extremum_offset == 0)
 105                                         error("Encountered a binary operator which lacks a left hand argument");
 106                                 else if(next_offset >= input.size())
 107                                         error("Encountered a binary operator which lacks a right hand argument");
 108
 109                                 parse_tree_nodes
 110                                         left_side(input.begin(), input.begin() + extremum_offset),
 111                                         right_side(input.begin() + next_offset, input.end());
 112
 113                                 operator_resolution(left_side, binary_operator_node.left_argument);
 114                                 operator_resolution(right_side, binary_operator_node.right_argument);
 115
 116                                 output = operator_node;
 117
 118                                 return;
 119                         }
 120
 121                         case parse_tree_node_type::call:
 122                                 call_check(extremum_offset);
 123                                 operator_node.call_pointer->function = input[0];
 124                                 input.erase(input.begin());
 125                                 break;
 126
 127                         case parse_tree_node_type::call_operator:
 128                         case parse_tree_node_type::spaced_call_operator:
 129                         {
 130                                 call_check(extremum_offset);
 131                                 operator_node.is_call();
 132                                 operator_node.call_pointer->function = input[0];
 133                                 input.erase(input.begin());
 134
 135                                 parse_tree_node & new_operator_node = input[0];
 136
 137                                 next_offset--;
 138                                 if(new_operator_node.type != parse_tree_node_type::spaced_call_operator && next_offset < input.size())
 139                                 {
 140                                         new_operator_node.call_pointer->arguments.push_back(input[next_offset]);
 141                                         input.erase(input.begin() + next_offset);
 142                                 }
 143                                 break;
 144                         }
 145
 146                         default:
 147                                 error("Invalid operator node type encountered during operator resolution");
 148                 }
 149
 150                 operator_resolution(input, output);
 151         }
 152 }