9.4.4.2 Integer literals

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本文介绍了C#中整数文字量的相关知识。整数文字量用于表示int、uint、long和ulong类型的值，有十进制和十六进制两种形式。其类型根据后缀确定，若超出ulong范围会编译报错，还说明了最小int和long值作为十进制整数文字量的特殊规则。

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9.4.4.2 Integer literals
Integer literals are used to write values of types int, uint, long, and
ulong. Integer literals have two possible
forms: decimal and hexadecimal.
integer-literal::
decimal-integer-literal
hexadecimal-integer-literal
decimal-integer-literal::
decimal-digits integer-type-suffixopt
decimal-digits::
decimal-digit
decimal-digits decimal-digit
C# LANGUAGE SPECIFICATION
58
decimal-digit:: one of
0 1 2 3 4 5 6 7 8 9
integer-type-suffix:: one of
U u L l UL Ul uL ul LU Lu lU lu
hexadecimal-integer-literal::
0x hex-digits integer-type-suffixopt
0X hex-digits integer-type-suffixopt
hex-digits::
hex-digit
hex-digits hex-digit
hex-digit:: one of
0 1 2 3 4 5 6 7 8 9 A B C D E F a b c d e f
The type of an integer literal is determined as follows:
?If the literal has no suffix, it has the first of these types in which
its value can be represented: int, uint,
long, ulong.
?If the literal is suffixed by U or u, it has the first of these types in
which its value can be represented: uint,
ulong.
?If the literal is suffixed by L or l, it has the first of these types in
which its value can be represented: long,
ulong.
?If the literal is suffixed by UL, Ul, uL, ul, LU, Lu, lU, or lu, it is of
type ulong.
If the value represented by an integer literal is outside the range of the
ulong type, a compile-time error occurs.
[Note: As a matter of style, it is suggested that .L. be used instead of
.l. when writing literals of type long,
since it is easy to confuse the letter .l. with the digit .1.. end note]
To permit the smallest possible int and long values to be written as
decimal integer literals, the following two
rules exist:
?When a decimal-integer-literal with the value 2147483648 (231) and no
integer-type-suffix appears as the
token immediately following a unary minus operator token (?4.6.2), the
result is a constant of type int with
the value -2147483648 (-231). In all other situations, such a
decimal-integer-literal is of type uint.
?When a decimal-integer-literal with the value 9223372036854775808 (263)
and no integer-type-suffix or the
integer-type-suffix L or l appears as the token immediately following a
unary minus operator token (?4.6.2),
the result is a constant of type long with the value -9223372036854775808
(-263). In all other situations,
such a decimal-integer-literal is of type ulong.