user-0 提问: 宏定义中的小数点

回复:
user: user-1
content: 宏就是替换，你写的是啥替换的就是啥

user: user-2
content: 关注点不对，这三个宏肯定是不一样的。 关注点应该在替换后的表达式。

user: user-3
content: 替换。。。。

user: user-4
content: #define就是替换而已，就像#define N  1+2 那么N*N 就是 1+2*1+2 结果为5而不是9 所以那里可以写整型、浮点型、函数等。 像你说的1000、1000.、1000.0  在函数中只是替换N

user: user-5
content: C++ Integer Constants Integer constants are constant data elements that have no fractional parts or exponents. They always begin with a digit. You can specify integer constants in decimal, octal, or hexadecimal form. They can specify signed or unsigned types and long or short types.  Syntax  integer-constant :  decimal-constant integer-suffixopt octal-constant integer-suffixopt hexadecimal-constant integer-suffixopt 'c-char-sequence'  decimal-constant :  nonzero-digit decimal-constant digit  octal-constant :  0 octal-constant octal-digit  hexadecimal-constant :  0x hexadecimal-digit 0X hexadecimal-digit hexadecimal-constant hexadecimal-digit  nonzero-digit : one of  1 2 3 4 5 6 7 8 9  octal-digit : one of  0 1 2 3 4 5 6 7  hexadecimal-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  integer-suffix :  unsigned-suffix long-suffixopt long-suffix unsigned-suffixopt  unsigned-suffix : one of  u U  long-suffix : one of  l L  64-bit integer-suffix :  i64  To specify integer constants using octal or hexadecimal notation, use a prefix that denotes the base. To specify an integer constant of a given integral type, use a suffix that denotes the type.  To specify a decimal constant, begin the specification with a nonzero digit. For example:  int i = 157;   // Decimal constant int j = 0198;  // Not a decimal number; erroneous octal constant int k = 0365;  // Leading zero specifies octal constant, not decimal  To specify an octal constant, begin the specification with 0, followed by a sequence of digits in the range 0 through 7. The digits 8 and 9 are errors in specifying an octal constant. For example:  int i = 0377;   // Octal constant int j = 0397;   // Error: 9 is not an octal digit  To specify a hexadecimal constant, begin the specification with 0x or 0X (the case of the “x” does not matter), followed by a sequence of digits in the range 0 through 9 and a (or A) through f (or F). Hexadecimal digits a (or A) through f (or F) represent values in the range 10 through 15. For example:  int i = 0x3fff;   // Hexadecimal constant int j = 0X3FFF;   // Equal to i  To specify an unsigned type, use either the u or U suffix. To specify a long type, use either the l or L suffix. For example:  unsigned uVal = 328u;             // Unsigned value long lVal = 0x7FFFFFL;            // Long value specified                                    //  as hex constant unsigned long ulVal = 0776745ul;  // Unsigned long value

user: user-6
content: 宏就是替换  #define XXXX       (1000)    --就是把XXXX出现的地方替换成 (1000)   #define XXXX       (1000.)   --就是把XXXX出现的地方替换成 (1000.)  #define XXXX       (1000.0   --就是把XXXX出现的地方替换成    (1000.0

user: user-7
content: 宏定义就是等价替换，实在预编译阶段将宏定义的部分全换成后面的部分。  因此1000和1000.0是有区别的，编译器区分这连个值是根据其类型来的，第一个按照整型，第二个就是按照浮点数来处理。

user: user-5
content: C++ Floating-Point Constants Floating-point constants specify values that must have a fractional part. These values contain decimal points (.) and can contain exponents.  Syntax  floating-constant :  fractional-constant exponent-partopt floating-suffixopt digit-sequence exponent-part floating-suffixopt  fractional-constant :  digit-sequenceopt . digit-sequence digit-sequence .  exponent-part :  e signopt digit-sequence E signopt digit-sequence  sign : one of  + –  digit-sequence :  digit digit-sequence digit  floating-suffix :one of  f l F L  Floating-point constants have a “mantissa,” which specifies the value of the number, an “exponent,” which specifies the magnitude of the number, and an optional suffix that specifies the constant’s type. The mantissa is specified as a sequence of digits followed by a period, followed by an optional sequence of digits representing the fractional part of the number. For example:  18.46 38.  The exponent, if present, specifies the magnitude of the number as a power of 10, as shown in the following example:  18.46e0      // 18.46 18.46e1      // 184.6  If an exponent is present, the trailing decimal point is unnecessary in whole numbers such as 18E0.  Floating-point constants default to type double. By using the suffixes f or l (or F or L — the suffix is not case sensitive), the constant can be specified as float or long double, respectively.  Although long double and double have the same representation, they are not the same type. For example, you can have overloaded functions like  void func( double );  and   void func( long double );

user: user-8
content: 1000. 和 1000.0 可以说没区别，都是double类型。1000. 后买自动填充0，具体多少个0，看系统而定。 1000  就不用说了吧。