/// <summary>
/// Process the "while" statement at "intermediate_code[index]".
/// </summary>
void process_while_statement(ref int index)
{
int start_while = statements.Count;
int end_while_label = LabelAddresses.allocate_label();
int start_index = index + 1;
// "start_index" is pointing to the first "while" statement, which marks
// the start of the while loop. The "while conditional:" line is further down.
// Search for the "while conditional:" line.
int conditional_index = start_index;
while (conditional_index < intermediate_code.Length)
{
if (intermediate_code[conditional_index][0].type == TokenType.While)
{
break;
}
conditional_index++;
}
// Generate statement for the code from "start_index" to
// "conditional_index"-1, if necessary
if (start_index < conditional_index)
{
construct_statements(start_index, conditional_index - 1, -1 * end_while_label, start_while);
}
// Generate statement for the "while conditional:" line
var conditional_line = intermediate_code[conditional_index];
int true_addr = statements.Count + 1;
statements.Add(new ConditionalStatement(conditional_line, true_addr, -1 * end_while_label));
// Find the end of the "while" body
int end_index = find_next_line_with_equal_or_less_indentation(conditional_index);
// Check for empty "while" body block
if (end_index - conditional_index <= 1)
{
throw new Exception("The while statement body is empty.");
}
// Generate statement for the "while" body
construct_statements(conditional_index + 1, end_index - 1, break_addr: -1 * end_while_label,
continue_addr: start_while);
// Generate statement for the end of the "while" body
int indentation = conditional_line.indentation + 4;
int line_number = intermediate_code[end_index - 1].line_number;
statements.Add(new JumpStatement(start_while, indentation, line_number));
index = end_index;
LabelAddresses.set_label_address(end_while_label, statements.Count);
}
/// <summary>
/// Process the "for" statement at "intermediate_code[index]".
/// </summary>
void process_for_statement(ref int index)
{
var for_statement = intermediate_code[index];
// extract the iterator and iteration variable
var iteration_var = for_statement[1];
var iterator = for_statement[3];
// add statement to reset the iterator
statements.Add(new FunctionCallStatement(iterator.ToString(), "reset", null,
for_statement.indentation, for_statement.line_number));
// mark the start of the for statement
int start_for = statements.Count;
// call iterator.has_next_element()
statements.Add(new FunctionCallStatement(iterator.ToString(), "has_next_element", null,
for_statement.indentation, for_statement.line_number));
// add conditional for the "for" decision
int end_for_label = LabelAddresses.allocate_label();
var for_condition = new TokenList(for_statement.line_number, for_statement.indentation);
for_condition.add_token(Token.Constants.If);
for_condition.add_token(Token.create_system_var("$return"));
for_condition.add_token(Token.Constants.Colon);
int true_addr = statements.Count + 1;
statements.Add(new ConditionalStatement(for_condition, true_addr, -1 * end_for_label));
// call iterator.next_element()
statements.Add(new FunctionCallStatement(iterator.ToString(), "next_element", null,
for_statement.indentation, for_statement.line_number));
// iteration_var = iterator
var assign_iteration_var = new TokenList(for_statement.line_number, for_statement.indentation);
assign_iteration_var.add_token(iteration_var);
assign_iteration_var.add_token(Token.Constants.Assign);
assign_iteration_var.add_token(Token.create_system_var("$return"));
statements.Add(new AssignStatement(assign_iteration_var));
// identify the for loop body
int end_index = find_next_line_with_equal_or_less_indentation(index);
// Check for empty "for" body block
if (end_index - index <= 1)
{
throw new Exception("The for statement body is empty.");
}
// generate code for "for" loop body
construct_statements(index + 1, end_index - 1, break_addr: -1 * end_for_label,
continue_addr: start_for);
// generate Jump at the end of the "for" loop body
int indentation = for_statement.indentation + 4;
int line_number = intermediate_code[end_index - 1].line_number;
statements.Add(new JumpStatement(start_for, indentation, line_number));
index = end_index;
LabelAddresses.set_label_address(end_for_label, statements.Count);
}
/// <summary>
/// Process the "if" statement at "intermediate_code[index]".
/// </summary>
void process_if_statement(ref int index, int?break_addr, int?continue_addr)
{
int end_if_final_label = LabelAddresses.allocate_label();
bool final_if_block = false;
while (final_if_block == false)
{
// "index" points to the current "if" line
// Find the end of the current if block
int end_index = find_next_line_with_equal_or_less_indentation(index);
var current_if_line = intermediate_code[index];
TokenList next_block_line = null;
if (end_index < intermediate_code.Length)
{
next_block_line = intermediate_code[end_index];
}
// Determine whether "next_block_line" is a continuation of the "if" statement.
if (next_block_line == null)
{
final_if_block = true; // end of the program
}
else if (next_block_line[0].type != TokenType.Elif &&
next_block_line[0].type != TokenType.Else)
{
final_if_block = true; // something other than "elif" and "else"
}
else if (next_block_line.indentation < current_if_line.indentation)
{
final_if_block = true; // end of if block due to indentation
}
// end_if_final --- label ID for the final "if" block's end address
// end_if --- label ID for the current "if" block's end address
int end_if_label = end_if_final_label;
if (final_if_block == false)
{
end_if_label = LabelAddresses.allocate_label();
}
// Generate statement for the current if line
if (current_if_line[0].type == TokenType.If ||
current_if_line[0].type == TokenType.Elif)
{
int true_addr = statements.Count + 1;
statements.Add(new ConditionalStatement(current_if_line, true_addr, -1 * end_if_label));
}
else if (current_if_line[0].type == TokenType.Else)
{
// do nothing
}
// Check for empty "if" body block
if (end_index - index <= 1)
{
if (current_if_line[0].type == TokenType.If)
{
throw new Exception("The if statement body is empty.");
}
else if (current_if_line[0].type == TokenType.Elif)
{
throw new Exception("The elif statement body is empty.");
}
else
{
throw new Exception("The else statement body is empty.");
}
}
// Generate statements for the "if" block body
construct_statements(index + 1, end_index - 1, break_addr, continue_addr);
// Generate statement for the end of the "if" block
if (final_if_block == false)
{
int indentation = intermediate_code[end_index - 1].indentation;
int line_number = intermediate_code[end_index - 1].line_number;
statements.Add(new JumpStatement(-1 * end_if_final_label, indentation, line_number));
}
// Record the current address as the "end_if" address
LabelAddresses.set_label_address(end_if_label, statements.Count);
// Set "index" for the future
index = end_index;
}
LabelAddresses.set_label_address(end_if_final_label, statements.Count);
}
/// <summary>
/// Process the "for" statement at "intermediate_code[index]".
/// </summary>
void process_def_statement(ref int index)
{
var def_statement = intermediate_code[index];
// A jump statement that goes to the end of the function
int end_func_label = LabelAddresses.allocate_label();
statements.Add(new JumpStatement(-1 * end_func_label, def_statement.indentation, def_statement.line_number));
// Syntax and assumption check
if (def_statement[1].type != TokenType.Identifier)
{
throw new Exception("Function definition syntax error. \""
+ def_statement[1].ToString() + "\" not an identifier.");
}
if (def_statement[2].type != TokenType.Left_Paren)
{
throw new Exception("Function definition syntax error. \""
+ def_statement[2].ToString() + "\" is expected to be '('.");
}
if (def_statement[-1].type != TokenType.Colon)
{
throw new Exception("Function definition syntax error. \""
+ "The function definition does not end with ':'.");
}
if (def_statement[-2].type != TokenType.Right_Paren)
{
throw new Exception("Function definition syntax error. \""
+ "The second last character is expected to be ')'.");
}
// Process function name
string function_name = (string)def_statement[1].value;
if (user_def_function_locations.ContainsKey(function_name))
{
throw new Exception("The function name \"" + function_name + "\" is already in use.");
}
user_def_function_locations.Add(function_name, statements.Count);
// Create a function argument assignment statement for each argument
int arg_index = 3; // def f ( arg0 -- start at arg0, token #3
int position_number = 0;
while (arg_index < def_statement.Count - 2)
{
// check that arg_index is an identifier token
if (def_statement[arg_index].type != TokenType.Identifier)
{
throw new Exception("Syntax error in function arguments. Expecting \""
+ def_statement[arg_index].ToString() + "\" to be a variable name.");
}
// simple argument case - without default argument, it's either [arg0 ,] or [arg0 )]
if (def_statement[arg_index + 1].type == TokenType.Comma ||
def_statement[arg_index + 1].type == TokenType.Right_Paren)
{
statements.Add(new FunctionArgAssignStatement(position_number, def_statement, arg_index, arg_index));
arg_index += 2;
position_number++;
}
// simple argument plus type hint: [arg0 : str]
else if (def_statement[arg_index + 1].type == TokenType.Colon &&
def_statement[arg_index + 2].type == TokenType.Identifier &&
(def_statement[arg_index + 3].type == TokenType.Comma ||
def_statement[arg_index + 3].type == TokenType.Right_Paren))
{
statements.Add(new FunctionArgAssignStatement(position_number, def_statement, arg_index, arg_index));
arg_index += 4;
position_number++;
}
// default argument case
else if (def_statement[arg_index + 1].type == TokenType.Assign)
{
// The end of the default argument could be a ',' or a ')'.
// In the case of ')', need to track '(' and ')' balance - since
// "x=(1+2)*3" is allowed in the default argument.
int arg_end_index = arg_index + 2;
int paren_balance = 0; // +1 for every '(' seen
while (arg_end_index < def_statement.Count - 1)
{
// t = current token
var t = def_statement[arg_end_index];
if (t.type == TokenType.Comma)
{
break;
}
else if (t.type == TokenType.Left_Paren)
{
paren_balance++;
}
else if (t.type == TokenType.Right_Paren)
{
paren_balance--;
if (paren_balance < 0)
{
break;
}
}
arg_end_index++;
}
// Look for errors with "arg_end_index"
// Check for parenthesis imbalance
if (def_statement[arg_end_index].type == TokenType.Comma &&
paren_balance != 0)
{
throw new Exception("The default argument has parenthesis imbalance.");
}
if (def_statement[arg_end_index].type == TokenType.Right_Paren &&
paren_balance != -1)
{
throw new Exception("The default argument has parenthesis imbalance.");
}
// Check empty default statement
if (arg_end_index == arg_index + 2)
{
throw new Exception("The default argument statement is empty.");
}
// Add argument assignment statement
statements.Add(new FunctionArgAssignStatement(position_number, def_statement, arg_index, arg_end_index - 1));
arg_index = arg_end_index + 1;
position_number++;
}
else
{
throw new Exception("Syntax error in function arguments.");
}
}
// Look for the end of the function block
int end_index = find_next_line_with_equal_or_less_indentation(index);
// Check for empty "def" body block
if (end_index - index <= 1)
{
throw new Exception("The " + def_statement.ToString().Trim()
+ " statement body is empty.");
}
// Generate statements for the function body
construct_statements(index + 1, end_index - 1, null, null);
// If there is no return statement, add one
var last_func_statement = statements[statements.Count - 1];
if (last_func_statement.Type != StatementType.Return)
{
statements.Add(new ReturnStatement(last_func_statement.Indentation, last_func_statement.LineNumber));
}
index = end_index;
LabelAddresses.set_label_address(end_func_label, statements.Count);
}