C++ parsetree_t::pop方法代码示例

void parser_t::Label() 
{
	parsetree.push(NT_Label);

	if(scanner.next_token() == T_label) 
	{
		eat_token(T_label);
		current = c_code_main;
		scanner.next_token();
		current = current + "\n L" + scanner.get_token_value() + ":\n ";
				// printf("current:\n%s\n", current.c_str());

		eat_token(T_num);
		eat_token(T_colon);
		LabelStatements();
		// printf("current:\n%s\n", current.c_str());

   
		c_code_main = current;
		current = c_code_main;
		printf("%s\n", c_code_main.c_str());

	}
	else { syntax_error(NT_Label); }
	parsetree.pop();
}

//Here is an example
void parser_t::Start()
{
  //push this non-terminal onto the parse tree.
  //the parsetree class is just for drawing the finished
  //parse tree, and should in should have no effect the actual
  //parsing of the data.
  parsetree.push(NT_Start);
  code_printf("#include <stdio.h>\n");
  
  code_printf("inline int intPow(int num, int e) {\n");
  code_printf("\tint res = 1;\n");
  code_printf("\tif(e>=0){\n");
  code_printf("\t\tfor(;e>0;e--)res = res*num;\n");
  code_printf("\t\treturn res;\n");
  code_printf("\t}\n");
  code_printf("\tif(num == 1) return 1;\n"); /* if e is negative 1^-a is 1*/
  code_printf("\treturn 0;\n");  /* if e is negative floor(1 ^-a) is 0*/ 
  code_printf("}\n");

  code_printf("int main(int argc, char *argv[]){\n");
  code_printf("\tint m[101];\n");
  // code_printf("\tint m[101];\n");

  Statements();

  code_printf("\treturn 0;\n");
  code_printf("}\n");

  parsetree.pop();
  

  
    
}

string parser_t::Jump(string s)
{
    token_type watch = scanner.next_token();
    parsetree.push(NT_Jump);
    if(watch == T_goto){
        eat_token(T_goto);
        s = Forward(s);
    }else{
        syntax_error(NT_Jump);
    }
    watch = scanner.next_token();
    switch(watch){
        case T_eof:
        case T_label:
        case T_goto:
        case T_m:
        case T_print:
            break;
        default:
            syntax_error(NT_Jump);
            break;
    }
    parsetree.pop();
    return s;
}

string parser_t::Label(string s)
{
    token_type watch = scanner.next_token();
    parsetree.push(NT_Label);
    if(watch == T_label){
        s.append("L");
        eat_token(T_label);
        eat_token(T_num);
        char buf[100];
        snprintf(buf, 100, "%d", scanner.nextNumber);
        s.append(buf);
        s.append(":");
        eat_token(T_colon);
    }else{
        syntax_error(NT_Label);
    }
    watch = scanner.next_token();
    switch(watch){
        case T_eof:
        case T_label:
        case T_goto:
        case T_m:
        case T_print:
            break;
        default:
            syntax_error(NT_Label);
            break;
    }
    parsetree.pop();
    return s;
}

void parser_t::Statement()
{
    string s;
    token_type watch = scanner.next_token();
    parsetree.push(NT_Statement);
    if(watch == T_label){
        s = Label(s);
    }else if(watch == T_goto){
        s = Jump(s);
    }else if(watch == T_m){
        s = Assignment(s);
    }else if(watch == T_print){
        s = Print(s);
    }else{
        syntax_error(NT_Statement);
    }
    cerr<<s<<";"<<endl;
    watch = scanner.next_token();
    switch(watch){
        case T_eof:
        case T_label:
        case T_goto:
        case T_m:
        case T_print:
            break;
        default:
            syntax_error(NT_Statement);
            break;
    }
    parsetree.pop();
}

void parser_t::Factor(){
  token_type token;
  parsetree.push(NT_Factor);
  code_printf("intPow(");
  switch(token = scanner.next_token()){
  case T_openparen:
    eat_token(T_openparen);
    code_printf("(");
    Expression();
    code_printf(")");
    eat_token(T_closeparen);
    break;
  case T_m:
    code_printf("m[");
    eat_token(T_m);
    eat_token(T_opensquare);
    Expression();
    eat_token(T_closesquare);
    code_printf("]");
    break;
  case T_num:
    code_printf("%d",scanner.get_num());
    eat_token(T_num);
    break;
  default:
    syntax_error(NT_Factor);
    /*
    fprintf(stderr, "%d Invalid factor: %s\n", scanner.get_line(), token_to_string(token));
    assert(0);
    */
  }
  Power();
  parsetree.pop();
}

string parser_t::Assignment(string s)
{
    token_type watch = scanner.next_token();
    parsetree.push(NT_Assignment);
    if(watch == T_m){
        s.append("m");
        eat_token(T_m);
        s.append("[");
        eat_token(T_opensquare);
        s = Expression(s);
        s.append("]");
        eat_token(T_closesquare);
        s.append("=");
        eat_token(T_equals);
        s = Expression(s);
    }else{
        syntax_error(NT_Print);
    }
    watch = scanner.next_token();
    switch(watch){
        case T_eof:
        case T_label:
        case T_goto:
        case T_m:
        case T_print:
            break;
        default:
            syntax_error(NT_Print);
            break;
    }
    parsetree.pop();
    return s;
}

void parser_t::Statement()
{
  parsetree.push(NT_Statement);
  code_printf("\t");
  switch(scanner.next_token()){
  case T_label:
    Label();
    break;
  case T_goto:
    Jump();
    code_printf(";\n");
    break;
  case T_m:
    Assignment();
    code_printf(";\n");
    break;
  case T_print:
    Print();
    code_printf(";\n");
    break;
  default:
    syntax_error(NT_Start);
    break;
  }

  parsetree.pop();
}

void parser_t::LabelStatements()
{
	parsetree.push(NT_LabelStatements);

	switch(scanner.next_token())
	{
		case T_m:
		case T_print:
			LabelStatement();
			LabelStatements();
			break;
		case T_goto:
		case T_label:
		case T_eof:
			parsetree.drawepsilon();
			break;
		default:
			syntax_error(NT_LabelStatement);
			break;
	}


	parsetree.pop();

}

void parser_t::Factor()
{
	parsetree.push(NT_Factor);

	if(scanner.next_token() == T_num) 
	{
		current = current + scanner.get_token_value();
		// printf("%s\n", current.c_str());
		eat_token(T_num);
	}
	else if(scanner.next_token() == T_m) 
	{
		eat_token(T_m);
		eat_token(T_opensquare);
		current = current + "m[";
		Expression();

		eat_token(T_closesquare);
		current = current + "]";
	}
	else { syntax_error(NT_Factor); }

	parsetree.pop();

}

void parser_t::Statement()
{
	parsetree.push(NT_Statement);
	current = c_code_main;
	// printf("%s\n", current.c_str());
	switch(scanner.next_token())
	{
		case T_label:
			Label();
			break;
		case T_goto:
			Jump();
			break;
		case T_m:
			Assignment();
			break;
		case T_print:
			Print();
			break;
		default:
			syntax_error(NT_Statement);
			break;
	}

	c_code_main = current;
	// printf("%s\n", c_code_main.c_str());
	parsetree.pop();
}

void parser_t::Jump()
{
	parsetree.push(NT_Jump);

	if(scanner.next_token() == T_goto)
	{
		eat_token(T_goto);
		scanner.next_token();
		std::string tmp =  scanner.get_token_value();
		eat_token(T_num);

		//If there's an if statement, handle it it.
		if(scanner.next_token() == T_if) {
			eat_token(T_if);
			current = current + "if(";
			Expression();
			current = current + " != 0) { ";
			current = current + "goto L" + tmp + "; }\n ";
		}
		else {
			current = current + " goto L" + tmp + ";\n ";
		}
	}
	else { syntax_error(NT_Jump); }

	parsetree.pop();
}

void parser_t::BracketTerm() {
	parsetree.push(NT_BracketTerm);

	switch (scanner.next_token()) {
		case T_openparen:
			scanner.eat_token(T_openparen);
			cerr_buffer.push_back("(");
			Expression();
			scanner.eat_token(T_closeparen);
			cerr_buffer.push_back(")");
			break;
		case T_m:
			scanner.eat_token(T_m);
			scanner.eat_token(T_opensquare);
			cerr_buffer.push_back("m[");
			Expression();
			scanner.eat_token(T_closesquare);
			cerr_buffer.push_back("]");
			break;
		case T_num:
			scanner.eat_token(T_num);
			cerr_buffer.push_back(scanner.get_number());
			break;
		default:
			syntax_error(NT_BracketTerm);
	}

	parsetree.pop();
}

void parser_t::Print(){
  parsetree.push(NT_Print);
  eat_token(T_print);
  code_printf("printf(\"%%d\\n\", ");
  Expression();
  code_printf(")"); 
  parsetree.pop();
}

void parser_t::Term() {
	parsetree.push(NT_Term);

	ExponentialTerm();
	TermRight();

	parsetree.pop();
}