Урок 11. Типы в PascalABC.NET. Создание своего типа

Приветствуем тебя, юный (или не очень юный) читатель нашего сайта! Сегодня мы с вами поговорим про типы в PascalABC.NET: числовые, символьные и логические. Они немного отличаются от стандартных типов Turbo Pascal.

Давайте вспомним какими могут быть величины? Об этом говорилось в отдельной статье. Сейчас мы быстренько все впомним. Любая величина может быть трех типов: числовой, символьной и логическй. Раньше мы использовали всего несколько типов (integer, real, boolean ), но пришло время расширить знания.

Все типы я буду оформлять в удобную табличку, хотя некоторые моменты буду пояснять. Таблица будет иметь три столбца: тип, размер в байтах, дапозон значений.

Важно! Все диапазоны и типы действительны только для PascalABC.NET, во Free Pascal и Turbo Pascal у этих типов будут другие значения. Например, в  PascalABC.NET тип integer имеет диапазон от -2147483648 до 2147483647, а в Turbo Pascal  у этого типа диапазон  от -32768 до 32767.

Числовые типы

Принято разделять числовые типы на две большие подгруппы: целые и вещественные.

Целые типы

Вещественные типы

Для удобства в Паскале заведены специальные константы, которые возвращают на свое место минимальное или максимальное значение разных типов. Ниже вы можете посмотреть таблицу, в которую занесены все константы.

Логический тип

В PascalABC.NET  только один логический тип — boolean. Про него была написана целая статья. Тип Boolean принимает значение true или false, и его размер — 1 байт.

Символьный тип и строки

Символьный тип

Символьный тип char занимает 2 байта и хранит Unicode-символ.

Чтобы не писать отдельную  статью про символьный тип, вкратце расскажу про него здесь. В   PascalABC.NET помимо стандартных функций chr  и ord, добавлены новые функции — ChrUnicode и OrdUnicode.

Chr(n) — функция, возвращающая символ с кодом n в кодировке Windows;
Ord(с) — функция, возвращающая значение типа byte, представляющее собой код символа c в кодировке Windows.

ChrUnicode(w) — возвращает символ с кодом w в кодировке Unicode;
OrdUnicode(с) — возвращает значение типа word, представляющее собой код символа c в кодировке Unicode.

Давайте поэкспериментируем, составим вот такую небольшую программку.

program Chr_Ord_Example;

begin
  writeln(ChrUnicode(30000));
  writeln(OrdUnicode('*'));
  writeln(Chr(42));
  writeln(Ord('*'));
end.

Этой программой я хочу проверить накладываются ли друг на друга кодировка Windows  и Unicode. Ниже, на скриншоте вы можете посмотреть результат работы программы.

Строковой тип

Строки имеют тип string, состоят из набора последовательно расположенных символов char и используются для представления текста.

Строки могут иметь произвольную длину.  Строки изменяемы.

Наверное, сейчас вы сомневаетесь в том, что в PascalABC.NET строки могут быть произвольной длины. Давайте проверим это с помощью небольшой программы.

program String_Example;

label m1;
begin
  var s: string; {Так как мы с вами работает в PascalABC.NET, то данная конструкция здесь не является ошибкой.}
  var n := 0; 
  s := 'HelluuHelluuuuuuuulluuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Helluuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! HHelluuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Ho! uuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Hlluuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! Huuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! HelluuHelluuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! uuuuuuuuuuuuuuuuuuuuuuo! HelluuHelluuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuoHelluuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! HelluuHelluuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! uuuuuuuuuuuuuuuuuuuuuuo! HelluuHelluuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! HelluuHelluuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! uuuuuuuuuuuuuuuuuuuuuuo! HelluuHelluuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuoHelluuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! HelluuHelluuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! uuuuuuuuuuuuuuuuuuuuuuo! HelluuHelluuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! HelluuHelluuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! uuuuuuuuuuuuuuuuuuuuuuo! HelluuHelluuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuoHelluuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! HelluuHelluuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! uuuuuuuuuuuuuuuuuuuuuuo! HelluuHelluuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo! uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuo!';
  writeln(Length(s)); {Функция length() возвращает длину строки.}
  m1: {ставим метку}
  s := s + s; {В программировании операция сложения, выполненная со строками, называется конкатенацией}
  Inc(n);
  if n < 11 then goto m1;
  writeln(Length(s));
end.

Кроме того, в PascalABC.NET реализованы размерные строки. Для их описания используется тип string[n], где n — константа целого типа, указывающая длину строки.

Перечислимый и диапазонный типы

Перечислимый тип

Перечислимый тип определяется упорядоченным набором идентификаторов. Чтобы объявить  новый тип, используется специальное слово — type. Его необходимо ставить перед var.

type
  typeName = (value1, value2,..., valueN);

Значения перечислимого типа занимают 4 байта. Каждое значение value представляет собой константу типа typeName, попадающую в текущее пространство имен.

Например:

type
  Month = (January, February, March, April, May, June, July, August, September, October, November, December);

К константе перечислимого типа можно обращаться непосредственно по имени, а можно использовать запись typeName.value, в которой имя константы уточняется именем перечислимого типа, к которому она принадлежит:

var
  a, b: month;

begin
  a := February;
  b := Month.August;
end.

Для значений перечислимого типа можно использовать функции Ord, Pred и Succ, а также процедуры Inc и Dec (Подробнее про эти функции и процедуры). Функция Ord возвращает порядковый номер значения в списке констант соответствующего перечислимого типа, нумерация при этом начинается с нуля.

program type_example;

type
  Month = (January, February, March, April, May, June, July, August, September, October, November, December);

var
  a, b: month;

begin
  a := February;
  b := Month.August;
  writeln(a,', ', b);
  Inc(a);
  b := pred(b);
  writeln(a,', ', b);
  writeln(Ord(a),', ', Ord(b));
end.

Диапазонный тип

Диапазонный тип представляет собой подмножество значений целого, символьного или перечислимого типа и описывается в виде a..b, где a — нижняя, b — верхняя граница интервального типа, a<b.

Пример.

program type_example;

type
  Month = (January, February, March, April, May, June, July, August, September, October, November, December);

var
  a : January..May;
  b : 1..10;
  c : 'a'..'z';

begin
  a := March;
  b := 2;
  c := 'b';
  b := pred(b);
  writeln(a,', ', b,', ', c);
end.

Тип, на основе которого строится диапазонный тип, называется базовым для этого диапазонного типа. Значения диапазонного типа занимают в памяти столько же, сколько и значения соответствующего базового типа.

На сегодня все! Урок получился объемным, но, надеюсь, понятным. Если же у вас возникли вопросы, напишите нам.