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int.dart
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// 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`.
///
/// **See also:**
/// * [num] the super class for [int].
/// * [Numbers](https://dart.dev/guides/language/numbers) in
/// [A tour of the Dart language](https://dart.dev/guides/language/language-tour).
abstract final class int extends num {
/// Integer value for [name] in the compilation configuration environment.
///
/// The compilation configuration environment is provided by the
/// surrounding tools which are compiling or running the Dart program.
/// The environment is a mapping from a set of string keys to their associated
/// string value.
/// The string value, or lack of a value, associated with a [name]
/// must be consistent across all calls to [String.fromEnvironment],
/// `int.fromEnvironment`, [bool.fromEnvironment] and [bool.hasEnvironment]
/// in a single program.
/// The string values can be directly accessed using
/// [String.fromEnvironment].
///
/// This constructor looks up the string value for [name],
/// then attempts to parse it as an integer, using the same syntax rules as
/// [int.parse]/[int.tryParse]. That is, it accepts decimal numerals
/// and hexadecimal numerals with a `0x` prefix, and it accepts a leading
/// minus sign.
/// If there is no value associated with [name] in the compilation
/// configuration environment, or if the associated string value cannot
/// be parsed as an integer, the value of the constructor invocation
/// is the [defaultValue] integer, which defaults to the integer zero.
///
/// The result is effectively the same as that of:
/// ```dart template:expression
/// int.tryParse(const String.fromEnvironment(name, defaultValue: ""))
/// ?? defaultValue
/// ```
/// except that the constructor invocation can be a constant value.
///
/// Example:
/// ```dart
/// const defaultPort = int.fromEnvironment("defaultPort", defaultValue: 80);
/// ```
/// In order to check whether a value is there at all, use
/// [bool.hasEnvironment]. Example:
/// ```dart
/// const int? maybeDeclared = bool.hasEnvironment("defaultPort")
/// ? int.fromEnvironment("defaultPort")
/// : null;
/// ```
///
/// The string value, or lack of a value, associated with a [name]
/// must be consistent across all calls to [String.fromEnvironment],
/// `int.fromEnvironment`, [bool.fromEnvironment] and [bool.hasEnvironment]
/// in a single program.
///
/// This constructor is only guaranteed to work when invoked as `const`.
/// It may work as a non-constant invocation on some platforms which
/// have access to compiler options at run-time, but most ahead-of-time
/// compiled platforms will not have this information.
external const factory int.fromEnvironment(String name,
{int defaultValue = 0});
/// 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]
///
/// If both operands are negative, the result is negative, otherwise
/// the result is non-negative.
/// ```dart
/// print((2 & 1).toRadixString(2)); // 0010 & 0001 -> 0000
/// print((3 & 1).toRadixString(2)); // 0011 & 0001 -> 0001
/// print((10 & 2).toRadixString(2)); // 1010 & 0010 -> 0010
/// ```
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 is negative.
///
/// Example:
/// ```dart
/// print((2 | 1).toRadixString(2)); // 0010 | 0001 -> 0011
/// print((3 | 1).toRadixString(2)); // 0011 | 0001 -> 0011
/// print((10 | 2).toRadixString(2)); // 1010 | 0010 -> 1010
/// ```
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.
///
/// Example:
/// ```dart
/// print((2 ^ 1).toRadixString(2)); // 0010 ^ 0001 -> 0011
/// print((3 ^ 1).toRadixString(2)); // 0011 ^ 0001 -> 0010
/// print((10 ^ 2).toRadixString(2)); // 1010 ^ 0010 -> 1000
/// ```
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, shiftAmount)`.
///
/// 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.
///
/// Example:
/// ```dart
/// print((3 << 1).toRadixString(2)); // 0011 -> 0110
/// print((9 << 2).toRadixString(2)); // 1001 -> 100100
/// print((10 << 3).toRadixString(2)); // 1010 -> 1010000
/// ```
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, shiftAmount)`.
///
/// It is an error if [shiftAmount] is negative.
///
/// Example:
/// ```dart
/// print((3 >> 1).toRadixString(2)); // 0011 -> 0001
/// print((9 >> 2).toRadixString(2)); // 1001 -> 0010
/// print((10 >> 3).toRadixString(2)); // 1010 -> 0001
/// print((-6 >> 2).toRadixString); // 111...1010 -> 111...1110 == -2
/// print((-85 >> 3).toRadixString); // 111...10101011 -> 111...11110101 == -11
/// ```
int operator >>(int shiftAmount);
/// Bitwise unsigned right shift by [shiftAmount] bits.
///
/// The least significant [shiftAmount] bits are dropped,
/// the remaining bits (if any) are shifted down,
/// and zero-bits are shifted in as the new most significant bits.
///
/// The [shiftAmount] must be non-negative.
///
/// Example:
/// ```dart
/// print((3 >>> 1).toRadixString(2)); // 0011 -> 0001
/// print((9 >>> 2).toRadixString(2)); // 1001 -> 0010
/// print(((-9) >>> 2).toRadixString(2)); // 111...1011 -> 001...1110 (> 0)
/// ```
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.
///
/// Example:
/// ```dart
/// print(4.gcd(2)); // 2
/// print(8.gcd(4)); // 4
/// print(10.gcd(12)); // 2
/// print(10.gcd(0)); // 10
/// print((-2).gcd(-3)); // 1
/// ```
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`.
/// ```dart
/// 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].
/// ```dart
/// (-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:
/// ```dart
/// 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.
/// ```dart
/// 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].
///
/// ```dart
/// // 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:
/// ```dart
/// 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.
/// ```dart
/// 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 `value`,
/// the result is the same as `value < 0 ? -value : value`.
///
/// Integer overflow may cause the result of `-value` to stay negative.
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 [int] 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 and 'z' being 35.
///
/// The [radix] argument must be an integer in the range 2 to 36.
///
/// Example:
/// ```dart
/// // Binary (base 2).
/// print(12.toRadixString(2)); // 1100
/// print(31.toRadixString(2)); // 11111
/// print(2021.toRadixString(2)); // 11111100101
/// print((-12).toRadixString(2)); // -1100
/// // Octal (base 8).
/// print(12.toRadixString(8)); // 14
/// print(31.toRadixString(8)); // 37
/// print(2021.toRadixString(8)); // 3745
/// // Hexadecimal (base 16).
/// print(12.toRadixString(16)); // c
/// print(31.toRadixString(16)); // 1f
/// print(2021.toRadixString(16)); // 7e5
/// // Base 36.
/// print((35 * 36 + 1).toRadixString(36)); // z1
/// ```
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 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] string does not contain a valid integer literal,
/// optionally prefixed by a sign, a [FormatException] is thrown.
///
/// Rather than throwing and immediately catching the [FormatException],
/// instead use [tryParse] to handle a potential parsing error.
///
/// Example:
/// ```dart
/// var value = int.tryParse(text);
/// if (value == null) {
/// // handle the problem
/// // ...
/// }
/// ```
external static int parse(String source, {int? radix});
/// Parse [source] as a, possibly signed, integer literal.
///
/// Like [parse] except that this function returns `null` where a
/// similar call to [parse] would throw a [FormatException].
///
/// Example:
/// ```dart
/// print(int.tryParse('2021')); // 2021
/// print(int.tryParse('1f')); // null
/// // From binary (base 2) value.
/// print(int.tryParse('1100', radix: 2)); // 12
/// print(int.tryParse('00011111', radix: 2)); // 31
/// print(int.tryParse('011111100101', radix: 2)); // 2021
/// // From octal (base 8) value.
/// print(int.tryParse('14', radix: 8)); // 12
/// print(int.tryParse('37', radix: 8)); // 31
/// print(int.tryParse('3745', radix: 8)); // 2021
/// // From hexadecimal (base 16) value.
/// print(int.tryParse('c', radix: 16)); // 12
/// print(int.tryParse('1f', radix: 16)); // 31
/// print(int.tryParse('7e5', radix: 16)); // 2021
/// // From base 35 value.
/// print(int.tryParse('y1', radix: 35)); // 1191 == 34 * 35 + 1
/// print(int.tryParse('z1', radix: 35)); // null
/// // From base 36 value.
/// print(int.tryParse('y1', radix: 36)); // 1225 == 34 * 36 + 1
/// print(int.tryParse('z1', radix: 36)); // 1261 == 35 * 36 + 1
/// ```
external static int? tryParse(String source, {int? radix});
}