const
  SEEK_SET* = 0; SEEK_CUR* = 1; SEEK_END* = 2;

  TOKEN_IDENTIFIER* = 1; TOKEN_IF* = 2; TOKEN_THEN* = 3; TOKEN_ELSE* = 4; TOKEN_ELSIF* = 5;
  TOKEN_WHILE* = 6; TOKEN_DO* = 7; TOKEN_PROC* = 8; TOKEN_BEGIN* = 9; TOKEN_END* = 10;
  TOKEN_EXTERN* = 11; TOKEN_CONST* = 12; TOKEN_VAR* = 13; TOKEN_ARRAY* = 14; TOKEN_OF* = 15;
  TOKEN_TYPE* = 16; TOKEN_RECORD* = 17; TOKEN_UNION* = 18; TOKEN_POINTER* = 19; TOKEN_TO* = 20;
  TOKEN_BOOLEAN* = 21; TOKEN_NIL* = 22; TOKEN_AND* = 23; TOKEN_OR* = 24; TOKEN_NOT* = 25;
  TOKEN_RETURN* = 26; TOKEN_CAST* = 27; TOKEN_AS* = 28; TOKEN_SIZEOF* = 29;
  TOKEN_LEFT_PAREN* = 30; TOKEN_RIGHT_PAREN* = 31; TOKEN_LEFT_SQUARE* = 32;
  TOKEN_RIGHT_SQUARE* = 33; TOKEN_GREATER_EQUAL* = 34; TOKEN_LESS_EQUAL* = 35;
  TOKEN_GREATER_THAN* = 36; TOKEN_LESS_THAN* = 37; TOKEN_NOT_EQUAL* = 38; TOKEN_EQUAL* = 39;
  TOKEN_SEMICOLON* = 40; TOKEN_DOT* = 41; TOKEN_COMMA* = 42;
  TOKEN_PLUS* = 43; TOKEN_MINUS* = 44; TOKEN_MULTIPLICATION* = 45; TOKEN_DIVISION* = 46;
  TOKEN_REMAINDER* = 47; TOKEN_ASSIGNMENT* = 48; TOKEN_COLON* = 49; TOKEN_HAT* = 50;
  TOKEN_AT* = 51; TOKEN_COMMENT* = 52; TOKEN_INTEGER* = 53; TOKEN_WORD* = 54;
  TOKEN_CHARACTER* = 55; TOKEN_STRING* = 56; TOKEN_DEFER* = 57;

type
  Position* = record
    line: Word;
	column: Word
  end,
  Location* = record
    first: Position;
	last: Position
  end,
  SourceCode = record
    position: Position;
	text: String
  end,
  TokenValue* = union
    int_value: Int;
    string_value: pointer to Char;
    string: String;
	boolean_value: Bool;
	char_value: Char
  end,
  Token* = record
    kind: Int;
    value: TokenValue;
	location: Location
  end,
  FILE* = record
    dummy: Int
  end,
  CommandLine* = record
    input: pointer to Char;
	tokenize: Bool;
	syntax_tree: Bool
  end,
  Literal* = record
    value: Int
  end,
  ConstantDefinition* = record
    name: pointer to Char;
    body: pointer to Literal
  end,
  ConstantPart* = record
    elements: pointer to pointer to ConstantDefinition;
	count: Word
  end,
  Program* = record
    constants: ConstantPart
  end;

(*
  External procedures.
*)
proc fopen(pathname: pointer to Char, mode: pointer to Char): pointer to FILE; extern
proc fclose(stream: pointer to FILE): Int; extern
proc fseek(stream: pointer to FILE, off: Int, whence: Int): Int; extern
proc rewind(stream: pointer to FILE); extern
proc ftell(stream: pointer to FILE): Int; extern
proc fread(ptr: pointer to Byte, size: Word, nmemb: Word, stream: pointer to FILE): Word; extern
proc write(fd: Int, buf: pointer to Byte, Word: Int): Int; extern

proc malloc(size: Word): pointer to Byte; extern
proc free(ptr: pointer to Byte); extern
proc calloc(nmemb: Word, size: Word): pointer to Byte; extern
proc realloc(ptr: pointer to Byte, size: Word): pointer to Byte; extern

proc memset(ptr: pointer to Char, c: Int, n: Int): pointer to Char; extern

proc strcmp(s1: pointer to Char, s2: pointer to Char): Int; extern
proc strncmp(s1: pointer to Char, s2: pointer to Char, n: Word): Int; extern
proc strncpy(dst: pointer to Char, src: pointer to Char, dsize: Word): pointer to Char; extern
proc strcpy(dst: pointer to Char, src: pointer to Char): pointer to Char; extern
proc strlen(ptr: pointer to Char): Word; extern

proc strtol(nptr: pointer to Char, endptr: pointer to pointer to Char, base: Int): Int; extern

proc perror(s: pointer to Char); extern
proc exit(code: Int); extern

(*
  Standard procedures.
*)
proc reallocarray(ptr: pointer to Byte, n: Word, size: Word): pointer to Byte;
begin
  return realloc(ptr, n * size)
end

proc write_s(value: String);
begin
  write(0, value.ptr, value.length)
end

proc write_z(value: pointer to Char);
begin
  write(0, value, strlen(value))
end

proc write_b(value: Bool);
begin
  if value then
    write_s("true")
  else
    write_s("false")
  end
end

proc write_c(value: Char);
begin
  write(0, @value, 1)
end

proc write_i(value: Int);
var
  digit: Int, n: Int,
  buffer: array 10 of Char;
begin
  n := 9;
  buffer[9] := '0';

  if value = 0 then
    write_c('0')
  end;
  while value <> 0 do
    digit := value % 10;
	value := value / 10;

	buffer[n] := cast(cast('0' as Int) + digit as Char);
	n := n - 1
  end;
  while n < 9 do
    n := n + 1;
    write_c(buffer[n])
  end
end

proc write_u(value: Word);
begin
  write_i(value)
end

proc is_digit(c: Char): Bool;
begin
  return cast(c as Int) >= cast('0' as Int) and cast(c as Int) <= cast('9' as Int)
end

proc is_alpha(c: Char): Bool;
begin
  return cast(c as Int) >= cast('A' as Int) and cast(c as Int) <= cast('z' as Int)
end

proc is_alnum(c: Char): Bool;
begin
  return is_digit(c) or is_alpha(c)
end

proc is_space(c: Char): Bool;
begin
  return c = ' ' or c = '\n' or c = '\t'
end

proc string_equals(this: String, that: String): Bool;
begin
  if this.length <> that.length then
    return false
  end;
  return strncmp(this.ptr, that.ptr, this.length) = 0
end

proc open_substring(string: String, start: Word): String;
begin
  string.ptr := string.ptr + start;
  string.length := string.length - start;
  return string
end

proc substring(string: String, start: Word, count: Word): String;
begin
  string.ptr := string.ptr + start;
  string.length := count
end

proc string_dup(origin: String): String;
var
  copy: pointer to Char;
begin
  copy := cast(malloc(origin.length) as pointer to Char);
  strncpy(copy, origin.ptr, origin.length);
  origin.ptr := copy;

  return origin
end

proc char_at(string: String, position: Word): Char;
begin
  return (string.ptr + position)^
end

(*
  End of standard procedures.
*)

proc make_position(): Position;
var
  result: Position;
begin
  result.line := 1u;
  result.column := 1u;
  return result
end

proc read_source(filename: pointer to Char, result: pointer to String): Bool;
var
  input_file: pointer to FILE,
  source_size: Int,
  input: pointer to Byte;
begin
  input_file := fopen(filename, "rb\0".ptr);

  if input_file = nil then
    return false
  end;
  defer
    fclose(input_file)
  end;
  if fseek(input_file, 0, SEEK_END) <> 0 then
    return false
  end;
  source_size := ftell(input_file);
  if source_size < 0 then
    return false
  end;
  rewind(input_file);

  input := malloc(source_size);
  if fread(input, source_size, 1, input_file) <> 1u then
    return false
  end;
  result^.length := cast(source_size as Word);
  result^.ptr := cast(input as pointer to Char);

  return true
end

proc escape_char(escape: Char, result: pointer to Char): Bool;
begin
  if escape = 'n' then
	result^ := '\n';
	return true
  elsif escape = 'a' then
	result^ := '\a';
	return true
  elsif escape = 'b' then
	result^ := '\b';
	return true
  elsif escape = 't' then
	result^ := '\t';
	return true
  elsif escape = 'f' then
	result^ := '\f';
	return true
  elsif escape = 'r' then
	result^ := '\r';
	return true
  elsif escape = 'v' then
	result^ := '\v';
	return true
  elsif escape = '\\' then
	result^ := '\\';
	return true
  elsif escape = '\'' then
	result^ := '\'';
	return true
  elsif escape = '"' then
	result^ := '"';
	return true
  elsif escape = '?' then
	result^ := '\?';
	return true
  elsif escape = '0' then
	result^ := '\0';
	return true
  else
	return false
  end
end

proc advance_source(source_code: SourceCode, length: Word): SourceCode;
begin
  source_code.text := open_substring(source_code.text, length);
  source_code.position.column := source_code.position.column + length;

  return source_code
end

proc skip_spaces(source_code: SourceCode): SourceCode;
begin
  while source_code.text.length > 0u and is_space(char_at(source_code.text, 0)) do
    if char_at(source_code.text, 0) = '\n' then
      source_code.position.line := source_code.position.line + 1u;
      source_code.position.column := 1u
	else
	  source_code.position.column := source_code.position.column + 1u
	end;
    source_code.text := open_substring(source_code.text, 1u)
  end;
  return source_code
end

proc lex_identifier(source_code: pointer to SourceCode, token_content: pointer to String);
var
  content_length: Word;
begin
  content_length := 0u;
  token_content^ := source_code^.text;

  while is_alnum(char_at(source_code^.text, 0)) or char_at(source_code^.text, 0) = '_' do
    content_length := content_length + 1u;
	source_code^ := advance_source(source_code^, 1u)
  end;
  token_content^ := substring(token_content^, 0u, content_length)
end

proc lex_comment(source_code: pointer to SourceCode, token_content: pointer to String): Bool;
var
  content_length: Word;
begin
  content_length := 0u;
  token_content^ := source_code^.text;

  while source_code^.text.length > 1u do
    if char_at(source_code^.text, 0) = '*' and char_at(source_code^.text, 1) = ')' then
	  source_code^ := advance_source(source_code^, 2u);
	  token_content^ := substring(token_content^, 0, content_length);

	  return true
	end;
    content_length := content_length + 1u;
	source_code^ := advance_source(source_code^, 1)
  end;

  return false
end

proc lex_character(input: pointer to Char, current_token: pointer to Token): pointer to Char;
begin
  if input^ = '\\' then
    input := input + 1;
	if escape_char(input^, @current_token^.value.char_value) then
	  input := input + 1
	end
  elsif input^ <> '\0' then
    current_token^.value.char_value := input^;
	input := input + 1
  end;
  return input
end

proc lex_string(input: pointer to Char, current_token: pointer to Token): pointer to Char;
var
  token_end: pointer to Char,
  constructed_string: pointer to Char,
  token_length: Word,
  is_valid: Bool;
begin
  token_end := input;

  while token_end^ <> '\0' and not ((token_end - 1)^ <> '\\' and token_end^ = '"') do
    token_end := token_end + 1
  end;
  if token_end^ <> '\"' then
    return input
  end;
  token_length := cast(token_end - input as Word);
  current_token^.value.string_value := cast(calloc(token_length, 1) as pointer to Char);

  is_valid := true;
  constructed_string := current_token^.value.string_value;
  while input < token_end and is_valid do

    if input^ = '\\' then
      input := input + 1;
      if escape_char(input^, constructed_string) then
        input := input + 1
	  else
	    is_valid := false
      end
    elsif input^ <> '\0' then
      constructed_string^ := input^;
      input := input + 1
    end;

    constructed_string := constructed_string + 1
  end;

  return token_end
end

proc print_tokens(tokens: pointer to Token, tokens_size: Word);
var
  current_token: pointer to Token,
  i: Word;
begin
  i := 0u;
  while i < tokens_size do
    current_token := tokens + i;

    if current_token^.kind = TOKEN_IF then
	  write_s("IF")
    elsif current_token^.kind = TOKEN_THEN then
	  write_s("THEN")
    elsif current_token^.kind = TOKEN_ELSE then
	  write_s("ELSE")
    elsif current_token^.kind = TOKEN_ELSIF then
	  write_s("ELSIF")
    elsif current_token^.kind = TOKEN_WHILE then
	  write_s("WHILE")
    elsif current_token^.kind = TOKEN_DO then
	  write_s("DO")
	elsif current_token^.kind = TOKEN_PROC then
	  write_s("PROC")
	elsif current_token^.kind = TOKEN_BEGIN then
	  write_s("BEGIN")
	elsif current_token^.kind = TOKEN_END then
	  write_s("END")
   	elsif current_token^.kind = TOKEN_EXTERN then
	  write_s("EXTERN")
	elsif current_token^.kind = TOKEN_CONST then
	  write_s("CONST")
	elsif current_token^.kind = TOKEN_VAR then
	  write_s("VAR")
   	elsif current_token^.kind = TOKEN_ARRAY then
	  write_s("ARRAY")
	elsif current_token^.kind = TOKEN_OF then
	  write_s("OF")
	elsif current_token^.kind = TOKEN_TYPE then
	  write_s("TYPE")
	elsif current_token^.kind = TOKEN_RECORD then
	  write_s("RECORD")
	elsif current_token^.kind = TOKEN_UNION then
	  write_s("UNION")
	elsif current_token^.kind = TOKEN_POINTER then
	  write_s("POINTER")
	elsif current_token^.kind = TOKEN_TO then
	  write_s("TO")
	elsif current_token^.kind = TOKEN_BOOLEAN then
	  write_s("BOOLEAN<");
	  write_b(current_token^.value.boolean_value);
	  write_c('>')
	elsif current_token^.kind = TOKEN_NIL then
	  write_s("NIL")
	elsif current_token^.kind = TOKEN_AND then
	  write_s("AND")
	elsif current_token^.kind = TOKEN_OR then
	  write_s("OR")
	elsif current_token^.kind = TOKEN_NOT then
	  write_s("NOT")
	elsif current_token^.kind = TOKEN_RETURN then
	  write_s("RETURN")
	elsif current_token^.kind = TOKEN_CAST then
	  write_s("CAST")
	elsif current_token^.kind = TOKEN_AS then
	  write_s("AS")
	elsif current_token^.kind = TOKEN_SIZEOF then
	  write_s("SIZEOF")
	elsif current_token^.kind = TOKEN_IDENTIFIER then
	  write_c('<');
      write_s(current_token^.value.string);
	  write_c('>')
	elsif current_token^.kind = TOKEN_LEFT_PAREN then
	  write_s("(")
	elsif current_token^.kind = TOKEN_RIGHT_PAREN then
	  write_s(")")
	elsif current_token^.kind = TOKEN_LEFT_SQUARE then
	  write_s("[")
	elsif current_token^.kind = TOKEN_RIGHT_SQUARE then
	  write_s("]")
	elsif current_token^.kind = TOKEN_GREATER_EQUAL then
	  write_s(">=")
	elsif current_token^.kind = TOKEN_LESS_EQUAL then
	  write_s("<=")
	elsif current_token^.kind = TOKEN_GREATER_THAN then
	  write_s(">")
	elsif current_token^.kind = TOKEN_LESS_THAN then
	  write_s("<")
	elsif current_token^.kind = TOKEN_EQUAL then
	  write_s("=")
	elsif current_token^.kind = TOKEN_NOT_EQUAL then
	  write_s("<>")
	elsif current_token^.kind = TOKEN_SEMICOLON then
	  write_c(';')
	elsif current_token^.kind = TOKEN_DOT then
	  write_c('.')
	elsif current_token^.kind = TOKEN_COMMA then
	  write_c(',')
	elsif current_token^.kind = TOKEN_PLUS then
	  write_c('+')
	elsif current_token^.kind = TOKEN_MINUS then
	  write_c('-')
	elsif current_token^.kind = TOKEN_MULTIPLICATION then
	  write_c('*')
	elsif current_token^.kind = TOKEN_DIVISION then
	  write_c('/')
	elsif current_token^.kind = TOKEN_REMAINDER then
	  write_c('%')
	elsif current_token^.kind = TOKEN_ASSIGNMENT then
	  write_s(":=")
	elsif current_token^.kind = TOKEN_COLON then
	  write_c(':')
	elsif current_token^.kind = TOKEN_HAT then
	  write_c('^')
	elsif current_token^.kind = TOKEN_AT then
	  write_c('@')
	elsif current_token^.kind = TOKEN_COMMENT then
	  write_s("(* COMMENT *)")
	elsif current_token^.kind = TOKEN_INTEGER then
	  write_c('<');
      write_i(current_token^.value.int_value);
	  write_c('>')
	elsif current_token^.kind = TOKEN_WORD then
	  write_c('<');
      write_i(current_token^.value.int_value);
	  write_s("u>")
	elsif current_token^.kind = TOKEN_CHARACTER then
	  write_c('<');
      write_i(current_token^.value.char_value);
	  write_s("c>")
	elsif current_token^.kind = TOKEN_STRING then
	  write_s("\"...\"")
	elsif current_token^.kind = TOKEN_DEFER then
	  write_s("DEFER")
	else
	  write_s("UNKNOWN<");
	  write_i(current_token^.kind);
	  write_c('>')
	end;
	write_c(' ');

	i := i + 1u
  end;
  write_c('\n')
end

proc categorize_identifier(token_content: String): Token;
var
  current_token: Token;
begin
  if string_equals("if", token_content) then
	current_token.kind := TOKEN_IF
  elsif string_equals("then", token_content) then
	current_token.kind := TOKEN_THEN
  elsif string_equals("else", token_content) then
	current_token.kind := TOKEN_ELSE
  elsif string_equals("elsif", token_content) then
	current_token.kind := TOKEN_ELSIF
  elsif string_equals("while", token_content) then
	current_token.kind := TOKEN_WHILE
  elsif string_equals("do", token_content) then
	current_token.kind := TOKEN_DO
  elsif string_equals("proc", token_content) then
	current_token.kind := TOKEN_PROC
  elsif string_equals("begin", token_content) then
	current_token.kind := TOKEN_BEGIN
  elsif string_equals("end", token_content) then
	current_token.kind := TOKEN_END
  elsif string_equals("extern", token_content) then
	current_token.kind := TOKEN_EXTERN
  elsif string_equals("const", token_content) then
	current_token.kind := TOKEN_CONST
  elsif string_equals("var", token_content) then
	current_token.kind := TOKEN_VAR
  elsif string_equals("array", token_content) then
	current_token.kind := TOKEN_ARRAY
  elsif string_equals("of", token_content) then
	current_token.kind := TOKEN_OF
  elsif string_equals("type", token_content) then
	current_token.kind := TOKEN_TYPE
  elsif string_equals("record", token_content) then
	current_token.kind := TOKEN_RECORD
  elsif string_equals("union", token_content) then
	current_token.kind := TOKEN_UNION
  elsif string_equals("pointer", token_content) then
	current_token.kind := TOKEN_POINTER
  elsif string_equals("to", token_content) then
	current_token.kind := TOKEN_TO
  elsif string_equals("true", token_content) then
	current_token.kind := TOKEN_BOOLEAN;
	current_token.value.boolean_value := true
  elsif string_equals("false", token_content) then
	current_token.kind := TOKEN_BOOLEAN;
	current_token.value.boolean_value := false
  elsif string_equals("nil", token_content) then
	current_token.kind := TOKEN_NIL
  elsif string_equals("and", token_content) then
	current_token.kind := TOKEN_AND
  elsif string_equals("or", token_content) then
	current_token.kind := TOKEN_OR
  elsif string_equals("not", token_content) then
	current_token.kind := TOKEN_NOT
  elsif string_equals("return", token_content) then
	current_token.kind := TOKEN_RETURN
  elsif string_equals("cast", token_content) then
	current_token.kind := TOKEN_CAST
  elsif string_equals("as", token_content) then
	current_token.kind := TOKEN_AS
  elsif string_equals("sizeof", token_content) then
	current_token.kind := TOKEN_SIZEOF
  elsif string_equals("defer", token_content) then
	current_token.kind := TOKEN_DEFER
  else
	current_token.kind := TOKEN_IDENTIFIER;
	current_token.value.string := string_dup(token_content)
  end;

  return current_token
end

proc tokenize(source_code: SourceCode, tokens_size: pointer to Word): pointer to Token;
var
  token_end: pointer to Char,
  tokens: pointer to Token,
  current_token: pointer to Token,
  token_length: Word,
  first_char: Char,
  token_content: String;
begin
  tokens_size^ := 0u;
  tokens := nil;
  source_code := skip_spaces(source_code);

  while source_code.text.length <> 0u do
	tokens := cast(reallocarray(tokens, tokens_size^ + 1u, sizeof(Token)) as pointer to Token);
    current_token := tokens + tokens_size^;
	first_char := char_at(source_code.text, 0);

    if is_alpha(first_char) or first_char = '_' then
      lex_identifier(@source_code, @token_content);
      current_token^ := categorize_identifier(token_content);

      source_code := advance_source(source_code, 1u)
	elsif is_digit(first_char) then
	  token_end := nil;
	  current_token^.value.int_value := strtol(source_code.text.ptr, @token_end, 10);
	  token_length := cast(token_end - source_code.text.ptr as Word);

	  if token_end^ = 'u' then
	    current_token^.kind := TOKEN_WORD;
        source_code := advance_source(source_code, token_length + 1u)
	  else
	    current_token^.kind := TOKEN_INTEGER;
        source_code := advance_source(source_code, token_length)
	  end
	elsif first_char = '(' then
	  source_code := advance_source(source_code, 1u);

	  if source_code.text.length = 0u then
	    current_token^.kind := TOKEN_LEFT_PAREN
	  elsif char_at(source_code.text, 0u) = '*' then
	    source_code := advance_source(source_code, 1u);

		if lex_comment(@source_code, @token_content) then
	      current_token^.value.string := string_dup(token_content);
		  current_token^.kind := TOKEN_COMMENT
		else
	      current_token^.kind := 0
		end
	  else
	    current_token^.kind := TOKEN_LEFT_PAREN
	  end
	elsif first_char = ')' then
	  current_token^.kind := TOKEN_RIGHT_PAREN;
	  source_code := advance_source(source_code, 1u)
	elsif first_char = '\'' then
	  token_end := lex_character(source_code.text.ptr + 1, current_token);
	  token_length := cast(token_end - source_code.text.ptr as Word);

	  if token_end^ = '\'' then
	  	current_token^.kind := TOKEN_CHARACTER;
	    source_code := advance_source(source_code, token_length + 1u)
	  else
	    source_code := advance_source(source_code, 1u)
	  end
	elsif first_char = '"' then
	  token_end := lex_string(source_code.text.ptr + 1, current_token);

      if token_end^ = '"' then
		current_token^.kind := TOKEN_STRING;
	    token_length := cast(token_end - source_code.text.ptr as Word);
	    source_code := advance_source(source_code, token_length + 1u)
	  end
	elsif first_char = '[' then
	  current_token^.kind := TOKEN_LEFT_SQUARE;
	  source_code := advance_source(source_code, 1u)
	elsif first_char = ']' then
	  current_token^.kind := TOKEN_RIGHT_SQUARE;
	  source_code := advance_source(source_code, 1u)
	elsif first_char = '>' then
	  source_code := advance_source(source_code, 1u);

      if source_code.text.length = 0u then
	    current_token^.kind := TOKEN_GREATER_THAN
	  elsif char_at(source_code.text, 0) = '=' then
	    current_token^.kind := TOKEN_GREATER_EQUAL;
	    source_code := advance_source(source_code, 1u)
	  else
	    current_token^.kind := TOKEN_GREATER_THAN
	  end
	elsif first_char = '<' then
	  source_code := advance_source(source_code, 1u);

	  if source_code.text.length = 0u then
	    current_token^.kind := TOKEN_LESS_THAN
	  elsif char_at(source_code.text, 0) = '=' then
	    current_token^.kind := TOKEN_LESS_EQUAL;
	    source_code := advance_source(source_code, 1u)
	  elsif char_at(source_code.text, 0) = '>' then
	    current_token^.kind := TOKEN_NOT_EQUAL;
	    source_code := advance_source(source_code, 1u)
	  else
	    current_token^.kind := TOKEN_LESS_THAN
	  end
	elsif first_char = '=' then
	  current_token^.kind := TOKEN_EQUAL;
	  source_code := advance_source(source_code, 1u)
	elsif first_char = ';' then
	  current_token^.kind := TOKEN_SEMICOLON;
	  source_code := advance_source(source_code, 1u)
	elsif first_char = '.' then
	  current_token^.kind := TOKEN_DOT;
	  source_code := advance_source(source_code, 1u)
	elsif first_char = ',' then
	  current_token^.kind := TOKEN_COMMA;
	  source_code := advance_source(source_code, 1u)
	elsif first_char = '+' then
	  current_token^.kind := TOKEN_PLUS;
	  source_code := advance_source(source_code, 1u)
	elsif first_char = '-' then
	  current_token^.kind := TOKEN_MINUS;
	  source_code := advance_source(source_code, 1u)
	elsif first_char = '*' then
	  current_token^.kind := TOKEN_MULTIPLICATION;
	  source_code := advance_source(source_code, 1u)
	elsif first_char = '/' then
	  current_token^.kind := TOKEN_DIVISION;
	  source_code := advance_source(source_code, 1u)
	elsif first_char = '%' then
	  current_token^.kind := TOKEN_REMAINDER;
	  source_code := advance_source(source_code, 1u)
	elsif first_char = ':' then
	  source_code := advance_source(source_code, 1u);

	  if source_code.text.length = 0u then
	    current_token^.kind := TOKEN_COLON
	  elsif char_at(source_code.text, 0) = '=' then
	    current_token^.kind := TOKEN_ASSIGNMENT;
	    source_code := advance_source(source_code, 1u)
	  else
	    current_token^.kind := TOKEN_COLON
	  end
	elsif first_char = '^' then
	  current_token^.kind := TOKEN_HAT;
	  source_code := advance_source(source_code, 1u)
	elsif first_char = '@' then
	  current_token^.kind := TOKEN_AT;
	  source_code := advance_source(source_code, 1u)
	else
	  current_token^.kind := 0;
	  source_code := advance_source(source_code, 1u)
	end;

	if current_token^.kind <> 0 then
      tokens_size^ := tokens_size^ + 1u;
      source_code := skip_spaces(source_code)
	else
	  write_s("Lexical analysis error on \"");
	  write_c(first_char);
	  write_s("\".\n")
	end
  end;

  return tokens
end

proc parse_literal(tokens: pointer to pointer to Token, tokens_size: pointer to Word): pointer to Literal;
begin
  return cast(calloc(1, sizeof(Literal)) as pointer to Literal)
end

proc parse_constant_definition(tokens: pointer to pointer to Token,
    tokens_size: pointer to Word): pointer to ConstantDefinition;
var
  result: pointer to ConstantDefinition;
begin
  result := cast(calloc(1, sizeof(ConstantDefinition)) as pointer to ConstantDefinition);

  result^.name := cast(malloc(strlen(tokens^^.value.string_value)) as pointer to Char);
  strcpy(result^.name, tokens^^.value.string_value);

  tokens^ := tokens^ + 2u;
  tokens_size := tokens_size - 2u;

  write_z(result^.name);
  write_c('\n');

  result^.body := parse_literal(tokens, tokens_size);

  tokens^ := tokens^ + 2u;
  tokens_size := tokens_size - 2u;

  return result
end

proc parse_program(tokens: pointer to pointer to Token, tokens_size: pointer to Word): pointer to Program;
var
  result: pointer to Program,
  current_constant: pointer to pointer to ConstantDefinition;
begin
  result := cast(calloc(1, sizeof(Program)) as pointer to Program);

  result^.constants.elements := nil;
  result^.constants.count := 0u;

  if tokens^^.kind = TOKEN_CONST then
    tokens^ := tokens^ + 1;
	tokens_size^ := tokens_size^ - 1u;

	while tokens_size^ > 0u and tokens^^.kind = TOKEN_IDENTIFIER do
	  result^.constants.elements := cast(
	      reallocarray(result^.constants.elements, result^.constants.count + 1u, sizeof(pointer to ConstantDefinition))
		  as pointer to pointer to ConstantDefinition);
      current_constant := result^.constants.elements + result^.constants.count;

	  result^.constants.count := result^.constants.count + 1u;

	  current_constant^ := parse_constant_definition(tokens, tokens_size);
	  if current_constant^ = nil then
	    return nil
	  end
	end
  end
end

proc parse_command_line*(argc: Int, argv: pointer to pointer to Char): pointer to CommandLine;
var
  parameter: pointer to pointer to Char,
  i: Int,
  result: pointer to CommandLine;
begin
  i := 1;
  result := cast(malloc(sizeof(CommandLine)) as pointer to CommandLine);
  result^.tokenize := false;
  result^.syntax_tree := false;
  result^.input := nil;

  while i < argc do
    parameter := argv + i;

    if strcmp(parameter^, "--tokenize\0".ptr) = 0 then
      result^.tokenize := true
    elsif strcmp(parameter^, "--syntax-tree\0".ptr) = 0 then
      result^.syntax_tree := true
    elsif parameter^^ <> '-' then
      result^.input := parameter^
    else
      write_s("Fatal error: Unknown command line options:");

      write_c(' ');
      write_z(parameter^);
      write_s(".\n");

      return nil
    end;

    i := i + 1
  end;
  if result^.input = nil then
    write_s("Fatal error: no input files.\n");
	return nil
  end;

  return result
end

proc process(argc: Int, argv: pointer to pointer to Char): Int;
var
  tokens: pointer to Token,
  tokens_size: Word,
  source_code: SourceCode,
  command_line: pointer to CommandLine;
begin
  command_line := parse_command_line(argc, argv);
  if command_line = nil then
    return 2
  end;

  source_code.position := make_position();
  if not read_source(command_line^.input, @source_code.text) then
    perror(command_line^.input);
	return 3
  end;
  tokens := tokenize(source_code, @tokens_size);

  if command_line^.tokenize then
    print_tokens(tokens, tokens_size)
  end;
  if command_line^.syntax_tree then
    parse_program(@tokens, @tokens_size)
  end;
  return 0
end

begin
  exit(process(count, parameters))
end.