interpreter.C

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#include <sstream>

#include "interpreter.H"

using namespace std;

namespace reranker {

using std::ostringstream;

void
Interpreter::Eval(StreamTokenizer &st) {
  // Keeps reading assignment statements until there are no more tokens.
  while (st.PeekTokenType() != StreamTokenizer::EOF_TYPE) {
    try {
    // Read variable name or type specifier.
    StreamTokenizer::TokenType token_type = st.PeekTokenType();
    VarMapBase *varmap = env_->GetVarMapForType(st.Peek());
    bool is_type_specifier =  varmap != NULL;
    if (token_type != StreamTokenizer::IDENTIFIER && !is_type_specifier) {
      string expected_type =
          string(StreamTokenizer::TypeName(StreamTokenizer::IDENTIFIER)) +
          " or type specifier";
      string found_type = StreamTokenizer::TypeName(token_type);
      WrongTokenTypeError(st.PeekTokenStart(), expected_type, found_type,
                          st.Peek());
    }

    string type = "";
    if (is_type_specifier) {
      // Consume and remember the type specifier.
      st.Next();              // Explicit type could be a concrete type.
      type = varmap->Name();  // Remember the abstract type.

      // Check that next token is a variable name.
      StreamTokenizer::TokenType token_type = st.PeekTokenType();
      if (token_type != StreamTokenizer::IDENTIFIER) {
        WrongTokenTypeError(st.PeekTokenStart(), StreamTokenizer::IDENTIFIER,
                            token_type, st.Peek());
      }
    }

    string varname = st.Next();

    // Next, read equals sign.
    token_type = st.PeekTokenType();
    if (st.Peek() != "=") {
      WrongTokenError(st.PeekTokenStart(), "=", st.Peek(), st.PeekTokenType());
    }

    // Consume equals sign.
    st.Next();

    if (st.PeekTokenType() == StreamTokenizer::EOF_TYPE) {
      ostringstream err_ss;
      err_ss << "Interpreter:" << filename_
             << ": error: unexpected EOF at stream position "
             << st.tellg();
      throw std::runtime_error(err_ss.str());
    }

    // Consume and set the value for this variable in the environment.
    env_->ReadAndSet(varname, st, type);

    token_type = st.PeekTokenType();
    if (st.Peek() != ";") {
      WrongTokenError(st.PeekTokenStart(), ";", st.Peek(), st.PeekTokenType());
    }
    // Consume semicolon.
    st.Next();
    }
    catch (std::runtime_error &e) {
      cerr << "threw exception: " << e.what() << endl;
      // For now, we simply give up.
      break;
    }
  }
}

void
Interpreter::WrongTokenError(size_t pos,
                             const string &expected,
                             const string &found,
                             StreamTokenizer::TokenType found_type) const {
  ostringstream err_ss;
  err_ss << "Interpreter:" << filename_ << ": at stream pos " << pos
         << " expected token \"" << expected << "\" but found \"" << found
         << "\" (token type: " << StreamTokenizer::TypeName(found_type)
         << ")";
  throw std::runtime_error(err_ss.str());
}

void
Interpreter::WrongTokenTypeError(size_t pos,
                                 StreamTokenizer::TokenType expected,
                                 StreamTokenizer::TokenType found,
                                 const string &token) const {
  WrongTokenTypeError(pos,
                      StreamTokenizer::TypeName(expected),
                      StreamTokenizer::TypeName(found),
                      token);
}

void
Interpreter::WrongTokenTypeError(size_t pos,
                                 const string &expected_type,
                                 const string &found_type,
                                 const string &token) const {
  ostringstream err_ss;
  err_ss << "Interpreter:" << filename_ << ": at stream pos " << pos
         << " expected token type " << expected_type
         << " but found " << found_type
         << "; token=\"" << token << "\"";
  throw std::runtime_error(err_ss.str());
}

}  // namespace reranker