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- 7.6.1Unary plus operator
- 7.6.2Unary minus operator
- 7.6.3Logical negation operator
- 7.6.4Bitwise complement operator
- 7.6.5Prefix increment and decrement operators
- 7.6.6Cast expressions
7.6Unary operatorsThe +, -, !, ~, ++, --, and cast operators are called the unary operators. unary-expression: primary-expression + unary-expression - unary-expression ! unary-expression ~ unary-expression pre-increment-expression pre-decrement-expression cast-expression 7.6.1Unary plus operatorFor an operation of the form +x, unary operator overload resolution (§7.2.3) is applied to select a specific operator implementation. The operand is converted to the parameter type of the selected operator, and the type of the result is the return type of the operator. The predefined unary plus operators are: int operator +(int x); uint operator +(uint x); long operator +(long x); ulong operator +(ulong x); float operator +(float x); double operator +(double x); decimal operator +(decimal x); For each of these operators, the result is simply the value of the operand. 7.6.2Unary minus operatorFor an operation of the form –x, unary operator overload resolution (§7.2.3) is applied to select a specific operator implementation. The operand is converted to the parameter type of the selected operator, and the type of the result is the return type of the operator. The predefined negation operators are:
int operator –(int x); long operator –(long x); The result is computed by subtracting x from zero. If the value of of x is the smallest representable value of the operand type (−231 for int or −263 for long), then the mathematical negation of x is not representable within the operand type. If this occurs within a checked context, a System.OverflowException is thrown; if it occurs within an unchecked context, the result is the value of the operand and the overflow is not reported. If the operand of the negation operator is of type uint, it is converted to type long, and the type of the result is long. An exception is the rule that permits the int value −2147483648 (−231) to be written as a decimal integer literal (§2.4.4.2). If the operand of the negation operator is of type ulong, a compile-time error occurs. An exception is the rule that permits the long value −9223372036854775808 (−263) to be written as a decimal integer literal (§2.4.4.2).
float operator –(float x); double operator –(double x); The result is the value of x with its sign inverted. If x is NaN, the result is also NaN.
decimal operator –(decimal x); The result is computed by subtracting x from zero. Decimal negation is equivalent to using the unary minus operator of type System.Decimal. 7.6.3Logical negation operatorFor an operation of the form !x, unary operator overload resolution (§7.2.3) is applied to select a specific operator implementation. The operand is converted to the parameter type of the selected operator, and the type of the result is the return type of the operator. Only one predefined logical negation operator exists: bool operator !(bool x); This operator computes the logical negation of the operand: If the operand is true, the result is false. If the operand is false, the result is true.
int operator ~(int x); uint operator ~(uint x); long operator ~(long x); ulong operator ~(ulong x); For each of these operators, the result of the operation is the bitwise complement of x. Every enumeration type E implicitly provides the following bitwise complement operator: E operator ~(E x); The result of evaluating ~x, where x is an expression of an enumeration type E with an underlying type U, is exactly the same as evaluating (E)(~(U)x).
The operand of a prefix increment or decrement operation must be an expression classified as a variable, a property access, or an indexer access. The result of the operation is a value of the same type as the operand. If the operand of a prefix increment or decrement operation is a property or indexer access, the property or indexer must have both a get and a set accessor. If this is not the case, a compile-time error occurs. Unary operator overload resolution (§7.2.3) is applied to select a specific operator implementation. Predefined ++ and -- operators exist for the following types: sbyte, byte, short, ushort, int, uint, long, ulong, char, float, double, decimal, and any enum type. The predefined ++ operators return the value produced by adding 1 to the operand, and the predefined -- operators return the value produced by subtracting 1 from the operand. In a checked context, if the result of this addition or subtraction is outside the range of the result type and the result type is an integral type or enum type, a System.OverflowException is thrown. The run-time processing of a prefix increment or decrement operation of the form ++x or --x consists of the following steps:
The ++ and -- operators also support postfix notation (§7.5.9). The result of x++ or x-- is the value of x before the operation, whereas the result of ++x or --x is the value of x after the operation. In either case, x itself has the same value after the operation. An operator ++ or operator -- implementation can be invoked using either postfix or prefix notation. It is not possible to have separate operator implementations for the two notations. 7.6.6Cast expressionsA cast-expression is used to explicitly convert an expression to a given type. cast-expression: ( type ) unary-expression A cast-expression of the form (T)E, where T is a type and E is a unary-expression, performs an explicit conversion (§6.2) of the value of E to type T. If no explicit conversion exists from E to T, a compile-time error occurs. Otherwise, the result is the value produced by the explicit conversion. The result is always classified as a value, even if E denotes a variable. The grammar for a cast-expression leads to certain syntactic ambiguities. For example, the expression (x)–y could either be interpreted as a cast-expression (a cast of –y to type x) or as an additive-expression combined with a parenthesized-expression (which computes the value x – y). To resolve cast-expression ambiguities, the following rule exists: A sequence of one or more tokens (§2.3.3) enclosed in parentheses is considered the start of a cast-expression only if at least one of the following are true:
The term “correct grammar” above means only that the sequence of tokens must conform to the particular grammatical production. It specifically does not consider the actual meaning of any constituent identifiers. For example, if x and y are identifiers, then x.y is correct grammar for a type, even if x.y doesn’t actually denote a type. From the disambiguation rule it follows that, if x and y are identifiers, (x)y, (x)(y), and (x)(-y) are cast-expressions, but (x)-y is not, even if x identifies a type. However, if x is a keyword that identifies a predefined type (such as int), then all four forms are cast-expressions (because such a keyword could not possibly be an expression by itself). Directory: download download -> Performance Tuning Guidelines for Windows Server 2008 May 20, 2009 Abstract download -> Northern England’s set-jetting locations download -> Bbc archives: Beyond the programme download download -> Occupational health and safety download -> Dynatest 3031 lwd light Weight Deflectometer download -> Forth coming competitive exams download -> English Olympiad Tasks: 10 th form Аудіювання, 10 клас. Текст download -> Brush High School Morning Announcements Friday, September 05, 2014 all school download -> Year 9 The Arts — Music download -> Years 7 and 8 standard elaborations — Australian Curriculum: Music draft Download 3.2 Mb. Share with your friends:
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