C# LANGUAGE SPECIFICATION

1A cast-expression of the form (T)E, where T is a type and E is a unary-expression, performs an explicit

2conversion (§13.2) of the value of E to type T. If no explicit conversion exists from the type of E to T, a

3compile-time error occurs. Otherwise, the result is the value produced by the explicit conversion. The result

4is always classified as a value, even if E denotes a variable.

5The grammar for a cast-expression leads to certain syntactic ambiguities. [Example: The expression

6(x)–y could either be interpreted as a cast-expression (a cast of –y to type x) or as an additive-

7 expression combined with a parenthesized-expression (which computes the value x – y). end example]

8To resolve cast-expression ambiguities, the following rule exists: A sequence of one or more tokens (§9.4)

9enclosed in parentheses is considered the start of a cast-expression only if at least one of the following are

10true:

11• The sequence of tokens is correct grammar for a type, but not for an expression.

12• The sequence of tokens is correct grammar for a type, and the token immediately following the closing

13parentheses is the token “~”, the token “!”, the token “(”, an identifier (§9.4.1), a literal (§9.4.4), or any

14keyword (§9.4.3) except as and is.

15The term “correct grammar” above means only that the sequence of tokens shall conform to the

16particular grammatical production. It specifically does not consider the actual meaning of any

17constituent identifiers. [Example: If x and y are identifiers, then x.y is correct grammar for a type, even

18if x.y doesn’t actually denote a type. end example]

19[Note: From the disambiguation rule, it follows that, if x and y are identifiers, (x)y, (x)(y), and

20(x)(-y) are cast-expressions, but (x)-y is not, even if x identifies a type. However, if x is a keyword

21that identifies a predefined type (such as int), then all four forms are cast-expressions (because such a

22keyword could not possibly be an expression by itself). end note]

2314.7 Arithmetic operators

24The *, /, %, +, and – operators are called the arithmetic operators.

25multiplicative-expression:

3414.7.1 Multiplication operator

35For an operation of the form x * y, binary operator overload resolution (§14.2.4) is applied to select a

36specific operator implementation. The operands are converted to the parameter types of the selected

37operator, and the type of the result is the return type of the operator.

38The predefined multiplication operators are listed below. The operators all compute the product of x and y.

39• Integer multiplication:

40int operator *(int x, int y);

41uint operator *(uint x, uint y);

42long operator *(long x, long y);

43ulong operator *(ulong x, ulong y);

44void operator *(long x, ulong y);

45void operator *(ulong x, long y);

46The operators with void return type always produce a compile-time error. Consequently, it is an error

47for one operand to be of type long and the other to be of type ulong.

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Chapter 14 Expressions

1In a checked context, if the product is outside the range of the result type, a

2System.OverflowException is thrown. In an unchecked context, overflows are not reported and

3any significant high-order bits outside the range of the result type are discarded.

4• Floating-point multiplication:

5float operator *(float x, float y);

6double operator *(double x, double y);

7The product is computed according to the rules of IEC 60559 arithmetic. The following table lists the

8results of all possible combinations of nonzero finite values, zeros, infinities, and NaN’s. In the table, x

9and y are positive finite values. z is the result of x * y, rounded to the nearest representable value. If

10the magnitude of the result is too large for the destination type, z is infinity. Because of rounding, z may

11be zero even though neither x nor y is zero.

12

13

14• Decimal multiplication:

15decimal operator *(decimal x, decimal y);

16If the magnitude of the resulting value is too large to represent in the decimal format, a

17System.OverflowException is thrown. Because of rounding, the result may be zero even though

18neither operand is zero. The scale of the result, before any rounding, is the sum of the scales of the two

19operands.

20Decimal multiplication is equivalent to using the multiplication operator of type System.Decimal.

2114.7.2 Division operator

22For an operation of the form x / y, binary operator overload resolution (§14.2.4) is applied to select a

23specific operator implementation. The operands are converted to the parameter types of the selected

24operator, and the type of the result is the return type of the operator.

25The predefined division operators are listed below. The operators all compute the quotient of x and y.

26• Integer division:

27int operator /(int x, int y);

28uint operator /(uint x, uint y);

29long operator /(long x, long y);

30ulong operator /(ulong x, ulong y);

31void operator /(long x, ulong y);

32void operator /(ulong x, long y);

33The operators with void return type always produce a compile-time error. Consequently, it is an error

34for one operand to be of type long and the other to be of type ulong.

35If the value of the right operand is zero, a System.DivideByZeroException is thrown.

36The division rounds the result towards zero, and the absolute value of the result is the largest possible

37integer that is less than the absolute value of the quotient of the two operands. The result is zero or

38positive when the two operands have the same sign and zero or negative when the two operands have

39opposite signs.

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1If the left operand is the smallest int or long value (−231 or −263, respectively) and the right operand is

2–1, an overflow occurs. In a checked context, this causes a System.ArithmeticException (or a

3subclass thereof) to be thrown. In an unchecked context, it is implementation-defined as to whether a

4System.ArithmeticException (or a subclass thereof) is thrown or the overflow goes unreported

5with the resulting value being that of the left operand.

6• Floating-point division:

7float operator /(float x, float y);

8double operator /(double x, double y);

9The quotient is computed according to the rules of IEC 60559 arithmetic. The following table lists the

10results of all possible combinations of nonzero finite values, zeros, infinities, and NaN’s. In the table, x

11and y are positive finite values. z is the result of x / y, rounded to the nearest representable value. If

12the magnitude of the result is too large for the destination type, z is infinity. Because of rounding, z may

13still be zero even though x is not zero and y is not infinite.

14

15

16• Decimal division:

17decimal operator /(decimal x, decimal y);

18If the value of the right operand is zero, a System.DivideByZeroException is thrown. If the

19magnituded of the resulting value is too large to represent in the decimal format, a

20System.OverflowException is thrown. Because of rounding, the result may be zero event though

21the first operand is not zero. The scale of the result, before any rounding, is the closest scale to the

22preferred scale which will preserve a result equal to the exact result. The preferred scale is the scale of x

23less the scale of y.

24Decimal division is equivalent to using the division operator of type System.Decimal.

2514.7.3 Remainder operator

26For an operation of the form x % y, binary operator overload resolution (§14.2.4) is applied to select a

27specific operator implementation. The operands are converted to the parameter types of the selected

28operator, and the type of the result is the return type of the operator.

29The predefined remainder operators are listed below. The operators all compute the remainder of the

30division between x and y.

31• Integer remainder:

32int operator %(int x, int y);

33uint operator %(uint x, uint y);

34long operator %(long x, long y);

35ulong operator %(ulong x, ulong y);

36void operator %(long x, ulong y);

37void operator %(ulong x, long y);

38The operators with void return type always produce a compile-time error. Consequently, it is an error

39for one operand to be of type long and the other to be of type ulong.

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Chapter 14 Expressions

1 The result of x % y is the value produced by x – (x / y) * y. If y is zero, a

2System.DivideByZeroException is thrown.

3If the left operand is the smallest int or long value (−231 or −263, respectively) and the right operand is

4–1, it is implementation-defined as to whether a System.ArithmeticException (or a subclass

7• Floating-point remainder:

8float operator %(float x, float y);

9double operator %(double x, double y);

10The following table lists the results of all possible combinations of nonzero finite values, zeros,

11infinities, and NaN’s. In the table, x and y are positive finite values. z is the result of x % y and is

12computed as x – n * y, rounded to the nearest representable value, where n is the largest integer that is

13less than or equal to x / y. This method of computing the remainder is analogous to that used for

14integer operands, but differs from the IEC 60559 definition (in which n is the integer closest to x / y).

15

16

17• Decimal remainder:

18decimal operator %(decimal x, decimal y);

19If the value of the right operand is zero, a System.DivideByZeroException is thrown. It is

20implementation-defined when a System.ArithmeticException (or a subclass thereof) is thrown. A

21 conforming implementation shall not throw an exception for x % y in any case where x / y does not

22throw an exception. The scale of the result, before any rounding, is the larger of the scales of the two

23operands, and the sign of the result, if non-zero, is the same as that of x.

24Decimal remainder is equivalent to using the remainder operator of type System.Decimal.

2514.7.4 Addition operator

26For an operation of the form x + y, binary operator overload resolution (§14.2.4) is applied to select a

27specific operator implementation. The operands are converted to the parameter types of the selected

28operator, and the type of the result is the return type of the operator.

29The predefined addition operators are listed below. For numeric and enumeration types, the predefined

30addition operators compute the sum of the two operands. When one or both operands are of type string,

31the predefined addition operators concatenate the string representation of the operands.

32• Integer addition:

33int operator +(int x, int y);

34uint operator +(uint x, uint y);

35long operator +(long x, long y);

36ulong operator +(ulong x, ulong y);

37void operator +(long x, ulong y);

38void operator +(ulong x, long y);

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C# LANGUAGE SPECIFICATION

1The operators with void return type always produce a compile-time error. Consequently, it is an error

2for one operand to be of type long and the other to be of type ulong.

3In a checked context, if the sum is outside the range of the result type, a

4System.OverflowException is thrown. In an unchecked context, overflows are not reported and

5any significant high-order bits outside the range of the result type are discarded.

6• Floating-point addition:

7float operator +(float x, float y);

8double operator +(double x, double y);

9The sum is computed according to the rules of IEC 60559 arithmetic. The following table lists the

10results of all possible combinations of nonzero finite values, zeros, infinities, and NaN’s. In the table, x

11and y are nonzero finite values, and z is the result of x + y, rounded to the nearest representable value.

12If x and y have the same magnitude but opposite signs, z is positive zero. If the magnitude of x + y is

13too large to represent in the destination type, z is an infinity with the same sign as x + y.

14

15

16• Decimal addition:

17decimal operator +(decimal x, decimal y);

18If the magnitude of the resulting value is too large to represent in the decimal format, a

19System.OverflowException is thrown. The scale of the result, before any rounding, is the larger of

20the scales of the two operands.

21Decimal addition is equivalent to using the addition operator of type System.Decimal.

22• Enumeration addition. Every enumeration type implicitly provides the following predefined operators,

23where E is the enum type, and U is the underlying type of E:

24E operator +(E x, U y);

25E operator +(U x, E y);

26The operators are evaluated exactly as (E)((U)x + (U)y). These operators are only considered by

27overload resolution (§14.2.4) when one of the actual operands is of type E.

28• String concatenation:

29string operator +(string x, string y);

30string operator +(string x, object y);

31string operator +(object x, string y);

32The binary + operator performs string concatenation when one or both operands are of type string. If

33an operand of string concatenation is null, an empty string is substituted. Otherwise, any non-string

34operand is converted to its string representation by invoking the virtual ToString method inherited

35from type object. If ToString returns null, an empty string is substituted. [Example:

36using System;

194