C + + Drip

1\\ C + + macros:

???? (1) # The function is to use the following macro parameters for string operation (stringfication);

???? Eg: #define WARN_IF (EXP)????

???? do{if (EXP)????

???????????????? fprintf (stderr, "Warning:" #EXP "\ n");}???

??????? ? while (0)

???? Wern_if (value = = 0);

???? expanded to :

???? do{

???????? if (value = = 0)

???????? fprintf (stderr, "warning:valude = = 0");

????} while (0);

???? (2) # # Connector ( concatenator ), used to set two of the token ( Mark ) connected to a token, Action object is no longer limited to macro parameters Span style= "font-family: Song body; Background-color:white "> can also be used with

???????? #define DECLARE_HANDLE (name) struct name# #__ {int unused;}; typedef struct name# #__ *name ( The pointer type for redefining the struct name# #__ is name)

???? Declare_handle (HWND);

???? HWND HD;

???? will get a struct pointer ;

???? --------------------------------------

???? Note : where the macro definition has # or ## the Place , macro parameters are not expanded

???? #define A 2;

???? #define PARAM (A) #A # #_;

???? printf ("%s", PARAM (A));

???? Get printf ("%s", A_);???? Compile error

???? macro Parameters A will not be unfolded as expected. 2_????

???? (3) C language predefined macros :

???? __date__
????date that the preprocessing was made ("Mmm dd yyyy"form of string literals)

???? __file__
????string literal representing the current source code file name

???? __line__
????An integer constant representing the line number in the current source code

???? __time__
????source file compilation time, Lattice micro"HH:mm:SS "

???? __FUNCTION__ (__fucn__)
????name of current function?

???? __date__, __time__ Yes build time if rebuild program __date__, __time__ and it changed.

2\\typedef:

???? structint__

???? {

???????? int A;

????};

???? typedefint__* pit;???????? // redefine int__ pointer type to pit

???? typedef int__ it

???? Pit pt = NULL;

???? Pt->a = 1000;

C + + Drip