sdk/lib/core/int.dart

// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

part of dart.core;

/**
 * An integer number.
 *
 * The default implementation of `int` is 64-bit two's complement integers
 * with operations that wrap to that range on overflow.
 *
 * **Note:** When compiling to JavaScript, integers are restricted to values
 * that can be represented exactly by double-precision floating point values.
 * The available integer values include all integers between -2^53 and 2^53,
 * and some integers with larger magnitude. That includes some integers larger
 * than 2^63.
 * The behavior of the operators and methods in the [int]
 * class therefore sometimes differs between the Dart VM and Dart code
 * compiled to JavaScript. For example, the bitwise operators truncate their
 * operands to 32-bit integers when compiled to JavaScript.
 *
 * Classes cannot extend, implement, or mix in `int`.
 */
abstract class int extends num {
  /**
   * Returns the integer value of the given environment declaration [name].
   *
   * The result is the same as would be returned by:
   * ```
   * int.tryParse(const String.fromEnvironment(name, defaultValue: ""))
   *     ?? defaultValue
   * ```
   * Example:
   * ```
   * const int.fromEnvironment("defaultPort", defaultValue: 80)
   * ```
   */
  // The .fromEnvironment() constructors are special in that we do not want
  // users to call them using "new". We prohibit that by giving them bodies
  // that throw, even though const constructors are not allowed to have bodies.
  // Disable those static errors.
  //ignore: const_constructor_with_body
  //ignore: const_factory
  external const factory int.fromEnvironment(String name, {int defaultValue});

  /**
   * Bit-wise and operator.
   *
   * Treating both `this` and [other] as sufficiently large two's component
   * integers, the result is a number with only the bits set that are set in
   * both `this` and [other]
   *
   * Of both operands are negative, the result is negative, otherwise
   * the result is non-negative.
   */
  int operator &(int other);

  /**
   * Bit-wise or operator.
   *
   * Treating both `this` and [other] as sufficiently large two's component
   * integers, the result is a number with the bits set that are set in either
   * of `this` and [other]
   *
   * If both operands are non-negative, the result is non-negative,
   * otherwise the result us negative.
   */
  int operator |(int other);

  /**
   * Bit-wise exclusive-or operator.
   *
   * Treating both `this` and [other] as sufficiently large two's component
   * integers, the result is a number with the bits set that are set in one,
   * but not both, of `this` and [other]
   *
   * If the operands have the same sign, the result is non-negative,
   * otherwise the result is negative.
   */
  int operator ^(int other);

  /**
   * The bit-wise negate operator.
   *
   * Treating `this` as a sufficiently large two's component integer,
   * the result is a number with the opposite bits set.
   *
   * This maps any integer `x` to `-x - 1`.
   */
  int operator ~();

  /**
   * Shift the bits of this integer to the left by [shiftAmount].
   *
   * Shifting to the left makes the number larger, effectively multiplying
   * the number by `pow(2, shiftIndex)`.
   *
   * There is no limit on the size of the result. It may be relevant to
   * limit intermediate values by using the "and" operator with a suitable
   * mask.
   *
   * It is an error if [shiftAmount] is negative.
   */
  int operator <<(int shiftAmount);

  /**
   * Shift the bits of this integer to the right by [shiftAmount].
   *
   * Shifting to the right makes the number smaller and drops the least
   * significant bits, effectively doing an integer division by
   *`pow(2, shiftIndex)`.
   *
   * It is an error if [shiftAmount] is negative.
   */
  int operator >>(int shiftAmount);

  /**
   * Returns this integer to the power of [exponent] modulo [modulus].
   *
   * The [exponent] must be non-negative and [modulus] must be
   * positive.
   */
  int modPow(int exponent, int modulus);

  /**
   * Returns the modular multiplicative inverse of this integer
   * modulo [modulus].
   *
   * The [modulus] must be positive.
   *
   * It is an error if no modular inverse exists.
   */
  int modInverse(int modulus);

  /**
   * Returns the greatest common divisor of this integer and [other].
   *
   * If either number is non-zero, the result is the numerically greatest
   * integer dividing both `this` and `other`.
   *
   * The greatest common divisor is independent of the order,
   * so `x.gcd(y)` is  always the same as `y.gcd(x)`.
   *
   * For any integer `x`, `x.gcd(x)` is `x.abs()`.
   *
   * If both `this` and `other` is zero, the result is also zero.
   */
  int gcd(int other);

  /** Returns true if and only if this integer is even. */
  bool get isEven;

  /** Returns true if and only if this integer is odd. */
  bool get isOdd;

  /**
   * Returns the minimum number of bits required to store this integer.
   *
   * The number of bits excludes the sign bit, which gives the natural length
   * for non-negative (unsigned) values.  Negative values are complemented to
   * return the bit position of the first bit that differs from the sign bit.
   *
   * To find the number of bits needed to store the value as a signed value,
   * add one, i.e. use `x.bitLength + 1`.
   * ```
   * x.bitLength == (-x-1).bitLength
   *
   * 3.bitLength == 2;     // 00000011
   * 2.bitLength == 2;     // 00000010
   * 1.bitLength == 1;     // 00000001
   * 0.bitLength == 0;     // 00000000
   * (-1).bitLength == 0;  // 11111111
   * (-2).bitLength == 1;  // 11111110
   * (-3).bitLength == 2;  // 11111101
   * (-4).bitLength == 2;  // 11111100
   * ```
   */
  int get bitLength;

  /**
   * Returns the least significant [width] bits of this integer as a
   * non-negative number (i.e. unsigned representation).  The returned value has
   * zeros in all bit positions higher than [width].
   * ```
   * (-1).toUnsigned(5) == 31   // 11111111  ->  00011111
   * ```
   * This operation can be used to simulate arithmetic from low level languages.
   * For example, to increment an 8 bit quantity:
   * ```
   * q = (q + 1).toUnsigned(8);
   * ```
   * `q` will count from `0` up to `255` and then wrap around to `0`.
   *
   * If the input fits in [width] bits without truncation, the result is the
   * same as the input.  The minimum width needed to avoid truncation of `x` is
   * given by `x.bitLength`, i.e.
   * ```
   * x == x.toUnsigned(x.bitLength);
   * ```
   */
  int toUnsigned(int width);

  /**
   * Returns the least significant [width] bits of this integer, extending the
   * highest retained bit to the sign.  This is the same as truncating the value
   * to fit in [width] bits using an signed 2-s complement representation.  The
   * returned value has the same bit value in all positions higher than [width].
   *
   * ```
   *                                V--sign bit-V
   * 16.toSigned(5) == -16   //  00010000 -> 11110000
   * 239.toSigned(5) == 15   //  11101111 -> 00001111
   *                                ^           ^
   * ```
   * This operation can be used to simulate arithmetic from low level languages.
   * For example, to increment an 8 bit signed quantity:
   * ```
   * q = (q + 1).toSigned(8);
   * ```
   * `q` will count from `0` up to `127`, wrap to `-128` and count back up to
   * `127`.
   *
   * If the input value fits in [width] bits without truncation, the result is
   * the same as the input.  The minimum width needed to avoid truncation of `x`
   * is `x.bitLength + 1`, i.e.
   * ```
   * x == x.toSigned(x.bitLength + 1);
   * ```
   */
  int toSigned(int width);

  /**
   * Return the negative value of this integer.
   *
   * The result of negating an integer always has the opposite sign, except
   * for zero, which is its own negation.
   */
  int operator -();

  /**
   * Returns the absolute value of this integer.
   *
   * For any integer `x`, the result is the same as `x < 0 ? -x : x`.
   */
  int abs();

  /**
   * Returns the sign of this integer.
   *
   * Returns 0 for zero, -1 for values less than zero and
   * +1 for values greater than zero.
   */
  int get sign;

  /** Returns `this`. */
  int round();

  /** Returns `this`. */
  int floor();

  /** Returns `this`. */
  int ceil();

  /** Returns `this`. */
  int truncate();

  /** Returns `this.toDouble()`. */
  double roundToDouble();

  /** Returns `this.toDouble()`. */
  double floorToDouble();

  /** Returns `this.toDouble()`. */
  double ceilToDouble();

  /** Returns `this.toDouble()`. */
  double truncateToDouble();

  /**
   * Returns a String-representation of this integer.
   *
   * The returned string is parsable by [parse].
   * For any `int` `i`, it is guaranteed that
   * `i == int.parse(i.toString())`.
   */
  String toString();

  /**
   * Converts [this] to a string representation in the given [radix].
   *
   * In the string representation, lower-case letters are used for digits above
   * '9', with 'a' being 10 an 'z' being 35.
   *
   * The [radix] argument must be an integer in the range 2 to 36.
   */
  String toRadixString(int radix);

  /**
   * Parse [source] as a, possibly signed, integer literal and return its value.
   *
   * The [source] must be either a non-empty sequence of base-[radix] digits,
   * optionally prefixed with a minus or plus sign ('-' or '+').
   *
   * The [radix] must be in the range 2..36. The digits used are
   * first the decimal digits 0..9, and then the letters 'a'..'z' with
   * values 10 through 35. Also accepts upper-case letters with the same
   * values as the lower-case ones.
   *
   * If no [radix] is given then it defaults to 10. In this case, the [source]
   * digits may also start with `0x`, in which case the number is interpreted
   * as a hexadecimal integer literal,
   * When `int` is implemented by 64-bit signed integers,
   * hexadecimal integer literals may represent values larger than
   * 2<sup>63</sup>, in which case the value is parsed as if it is an
   * *unsigned* number, and the resulting value is the corresponding
   * signed integer value.
   *
   * For any int `n` and valid radix `r`, it is guaranteed that
   * `n == int.parse(n.toRadixString(r), radix: r)`.
   *
   * If the [source] does not contain a valid integer literal,
   * optionally prefixed by a sign, a [FormatException] is thrown
   * (unless the deprecated [onError] parameter is used, see below).
   *
   * Instead of throwing and immediately catching the [FormatException],
   * instead use [tryParse] to handle a parsing error.
   * Example:
   * ```dart
   * var value = int.tryParse(text);
   * if (value == null) ... handle the problem
   * ```
   *
   * The [onError] parameter is deprecated and will be removed.
   * Instead of `int.parse(string, onError: (string) => ...)`,
   * you should use `int.tryParse(string) ?? (...)`.
   *
   * When source is not valid and [onError] is provided,
   * whenever a [FormatException] would be thrown,
   * [onError] is instead called with [source] as argument,
   * and the result of that call is returned by [parse].
   */
  external static int parse(String source,
      {int radix, @deprecated int onError(String source)});

  /**
   * Parse [source] as a, possibly signed, integer literal and return its value.
   *
   * Like [parse] except that this function returns `null` where a
   * similar call to [parse] would throw a [FormatException].
   */
  external static int tryParse(String source, {int radix});
}