// 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 arbitrarily large integer.
 *
 * **Note:** When compiling to JavaScript, integers are
 * implemented as JavaScript numbers. When compiling to JavaScript,
 * integers are therefore restricted to 53 significant bits because
 * all JavaScript numbers are double-precision floating point
 * values. The behavior of the operators and methods in the [int]
 * class therefore sometimes differs between the Dart VM and Dart code
 * compiled to JavaScript.
 *
 * It is a compile-time error for a class to attempt to extend or implement 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.parse(const String.fromEnvironment(name, defaultValue: ""),
   *               (_) => defaultValue)
   *
   * Example:
   *
   *     const int.fromEnvironment("defaultPort", defaultValue: 80)
   */
  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 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) == 32   // 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 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 literal, which effectively means that the `0x` is ignored
   * and the radix is instead set to 16.
   *
   * For any int [:n:] and radix [:r:], it is guaranteed that
   * [:n == int.parse(n.toRadixString(r), radix: r):].
   *
   * If the [source] is not a valid integer literal, optionally prefixed by a
   * sign, the [onError] is called with the [source] as argument, and its return
   * value is used instead. If no [onError] is provided, a [FormatException]
   * is thrown.
   *
   * The [onError] handler can be chosen to return `null`.  This is preferable
   * to to throwing and then immediately catching the [FormatException].
   * Example:
   *
   *     var value = int.parse(text, onError: (source) => null);
   *     if (value == null) ... handle the problem
   *
   * The [onError] function is only invoked if [source] is a [String]. It is
   * not invoked if the [source] is, for example, `null`.
   */
  external static int parse(String source,
                            { int radix,
                              int onError(String source) });
}