An immutable 32-bit signed integer, in the range -2^31, 2^31 - 1. Arithmetic operations may overflow in order to maintain this range.

class int32 implements intx {

 /**
  * The maximum positive value attainable by an [int32], namely
  * 2147483647.
  */
 static final int32 MAX_VALUE = const int32._internal(0x7FFFFFFF);

 /**
  * The minimum positive value attainable by an [int32], namely
  * -2147483648.
  */
 static int32 MIN_VALUE = const int32._internal(0x80000000);

 /**
  * An [int32] constant equal to 0.
  */
 static int32 ZERO = const int32._internal(0);

 /**
  * An [int32] constant equal to 1.
  */
 static int32 ONE = const int32._internal(1);

 /**
  * An [int32] constant equal to 2.
  */
 static int32 TWO = const int32._internal(2);

 // Hex digit char codes
 static final int _CC_0 = 48; // '0'.codeUnitAt(0)
 static final int _CC_9 = 57; // '9'.codeUnitAt(0)
 static final int _CC_a = 97; // 'a'.codeUnitAt(0)
 static final int _CC_z = 122; // 'z'.codeUnitAt(0)
 static final int _CC_A = 65; // 'A'.codeUnitAt(0)
 static final int _CC_Z = 90; // 'Z'.codeUnitAt(0)

 static int _decodeHex(int c) {
   if (c >= _CC_0 && c <= _CC_9) {
     return c - _CC_0;
   } else if (c >= _CC_a && c <= _CC_z) {
     return c - _CC_a + 10;
   } else if (c >= _CC_A && c <= _CC_Z) {
     return c - _CC_A + 10;
   } else {
     return -1; // bad char code
   }
 }

 /**
  * Parses a [String] in a given [radix] between 2 and 16 and returns an
  * [int32].
  */
 // TODO(rice) - Make this faster by converting several digits at once.
 static int32 parseRadix(String s, int radix) {
   if ((radix <= 1) || (radix > 16)) {
     throw "Bad radix: $radix";
   }
   int32 x = ZERO;
   for (int i = 0; i < s.length; i++) {
     int c = s.codeUnitAt(i);
     int digit = _decodeHex(c);
     if (digit < 0 || digit >= radix) {
       throw new Exception("Non-radix char code: $c");
     }
     x = (x * radix) + digit;
   }
   return x;
 }

 /**
  * Parses a decimal [String] and returns an [int32].
  */
 static int32 parseInt(String s) => new int32.fromInt(int.parse(s));

 /**
  * Parses a hexadecimal [String] and returns an [int32].
  */
 static int32 parseHex(String s) => parseRadix(s, 16);

 // Assumes i is <= 32-bit.
 static int _bitCount(int i) {
   // See "Hacker's Delight", section 5-1, "Counting 1-Bits".

   // The basic strategy is to use "divide and conquer" to
   // add pairs (then quads, etc.) of bits together to obtain
   // sub-counts.
   //
   // A straightforward approach would look like:
   //
   // i = (i & 0x55555555) + ((i >>  1) & 0x55555555);
   // i = (i & 0x33333333) + ((i >>  2) & 0x33333333);
   // i = (i & 0x0F0F0F0F) + ((i >>  4) & 0x0F0F0F0F);
   // i = (i & 0x00FF00FF) + ((i >>  8) & 0x00FF00FF);
   // i = (i & 0x0000FFFF) + ((i >> 16) & 0x0000FFFF);
   //
   // The code below removes unnecessary &'s and uses a
   // trick to remove one instruction in the first line.

   i -= ((i >> 1) & 0x55555555);
   i = (i & 0x33333333) + ((i >> 2) & 0x33333333);
   i = ((i + (i >> 4)) & 0x0F0F0F0F);
   i += (i >> 8);
   i += (i >> 16);
   return (i & 0x0000003F);
 }

 // Assumes i is <= 32-bit
 static int _numberOfLeadingZeros(int i) {
   i |= i >> 1;
   i |= i >> 2;
   i |= i >> 4;
   i |= i >> 8;
   i |= i >> 16;
   return _bitCount(~i);
 }

 static int _numberOfTrailingZeros(int i) => _bitCount((i & -i) - 1);

 // The internal value, kept in the range [MIN_VALUE, MAX_VALUE].
 final int _i;

 const int32._internal(int i) : _i = i;

 /**
  * Constructs an [int32] from an [int].  Only the low 32 bits of the input
  * are used.
  */
 int32.fromInt(int i) : _i = (i & 0x7fffffff) - (i & 0x80000000);

 // Convert an [int] or [intx] to an [int32].  Note that an [int64]
 // will be truncated.
 int _convert(other) {
   if (other == null) {
     throw new ArgumentError("null");
   } else if (other is intx) {
     return other.toInt32()._i;
   } else if (other is int) {
     return other;
   } else {
     throw new Exception("Can't retrieve 32-bit int from $other");
   }
 }

 // The +, -, * , &, |, and ^ operaters deal with types as follows:
 //
 // int32 + int => int32
 // int32 + int32 => int32
 // int32 + int64 => int64
 //
 // The %, ~/ and remainder operators return an int32 even with an int64
 // argument, since the result cannot be greater than the value on the
 // left-hand side:
 //
 // int32 % int => int32
 // int32 % int32 => int32
 // int32 % int64 => int32

 intx operator +(other) {
   if (other is int64) {
     return this.toInt64() + other;
   }
   return new int32.fromInt(_i + _convert(other));
 }

 intx operator -(other) {
   if (other is int64) {
     return this.toInt64() - other;
   }
   return new int32.fromInt(_i - _convert(other));
 }

 int32 operator -() => new int32.fromInt(-_i);

 intx operator *(other) {
   if (other is int64) {
     return this.toInt64() * other;
   }
   // TODO(rice) - optimize
   return (this.toInt64() * other).toInt32();
 }

 int32 operator %(other) {
   if (other is int64) {
     // Result will be int32
     return (this.toInt64() % other).toInt32();
   }
   return new int32.fromInt(_i % _convert(other));
 }

 int32 operator ~/(other) {
   if (other is int64) {
     // Result will be int32
     return (this.toInt64() ~/ other).toInt32();
   }
   return new int32.fromInt(_i ~/ _convert(other));
 }

 int32 remainder(other) {
   if (other is int64) {
     // Result will be int32
     int64 t = this.toInt64();
     return (t - (t ~/ other) * other).toInt32();
   }
   return this - (this ~/ other) * other;
 }

 int32 operator &(other) {
   if (other is int64) {
     return (this.toInt64() & other).toInt32();
   }
   return new int32.fromInt(_i & _convert(other));
 }

 int32 operator |(other) {
   if (other is int64) {
     return (this.toInt64() | other).toInt32();
   }
   return new int32.fromInt(_i | _convert(other));
 }

 int32 operator ^(other) {
   if (other is int64) {
     return (this.toInt64() ^ other).toInt32();
   }
   return new int32.fromInt(_i ^ _convert(other));
 }

 int32 operator ~() => new int32.fromInt(~_i);

 int32 operator <<(int n) {
   if (n < 0) {
     throw new ArgumentError("$n");
   }
   n &= 31;
   return new int32.fromInt(_i << n);
 }

 int32 operator >>(int n) {
   if (n < 0) {
     throw new ArgumentError("$n");
   }
   n &= 31;
   int value;
   if (_i >= 0) {
     value = _i >> n;
   } else {
     value = (_i >> n) | (0xffffffff << (32 - n));
   }
   return new int32.fromInt(value);
 }

 int32 shiftRightUnsigned(int n) {
   if (n < 0) {
     throw new ArgumentError("$n");
   }
   n &= 31;
   int value;
   if (_i >= 0) {
     value = _i >> n;
   } else {
     value = (_i >> n) & ((1 << (32 - n)) - 1);
   }
   return new int32.fromInt(value);
 }

 /**
  * Returns [true] if this [int32] has the same numeric value as the
  * given object.  The argument may be an [int] or an [intx].
  */
 bool operator ==(other) {
   if (other == null) {
     return false;
   }
   if (other is int64) {
     return this.toInt64() == other;
   }
   return _i == _convert(other);
 }

 int compareTo(Comparable other) {
   if (other is int64) {
     return this.toInt64().compareTo(other);
   }
   return _i.compareTo(_convert(other));
 }

 bool operator <(other) {
   if (other is int64) {
     return this.toInt64() < other;
   }
   return _i < _convert(other);
 }

 bool operator <=(other) {
   if (other is int64) {
     return this.toInt64() < other;
   }
   return _i <= _convert(other);
 }

 bool operator >(other) {
   if (other is int64) {
     return this.toInt64() < other;
   }
   return _i > _convert(other);
 }

 bool operator >=(other) {
   if (other is int64) {
     return this.toInt64() < other;
   }
   return _i >= _convert(other);
 }

 bool isEven() => (_i & 0x1) == 0;
 bool isMaxValue() => _i == 2147483647;
 bool isMinValue() => _i == -2147483648;
 bool isNegative() => _i < 0;
 bool isOdd() => (_i & 0x1) == 1;
 bool isZero() => _i == 0;

 int get hashCode => _i;

 int32 abs() => _i < 0 ? new int32.fromInt(-_i) : this;

 int numberOfLeadingZeros() => _numberOfLeadingZeros(_i);
 int numberOfTrailingZeros() => _numberOfTrailingZeros(_i);

 List<int> toBytes() {
   List<int> result = new List<int>(4);
   result[0] = _i & 0xff;
   result[1] = (_i >> 8) & 0xff;
   result[2] = (_i >> 16) & 0xff;
   result[3] = (_i >> 24) & 0xff;
   return result;
 }

 int toInt() => _i;
 int32 toInt32() => this;
 int64 toInt64() => new int64.fromInt(_i);

 String toString() => _i.toString();
 String toHexString() => _i.toRadixString(16);
 String toRadixString(int radix) => _i.toRadixString(radix);
}