实例：C语言宏的使用之"##"

最新推荐文章于 2024-01-18 22:59:11 发布

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本文深入探讨了C语言中宏替换的高级应用，包括如何在字符串操作中利用宏实现特定功能，以及宏如何与其他语言特性相结合，提高代码的可读性和效率。通过实例演示了如何在字符串拼接、变量替换等方面使用宏，为读者提供了实用的编程技巧。

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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define Beta "Beta"
#define Num_Beta 2
#define Gamma "Gamma"
#define Num_Gamma 3
#define Delta "Delta"
#define Num_Delta 4
#define Epsilon "Epsilon"
#define Num_Epsilon 5
#define Alpha "Alpha"
#define Num_Alpha 1
	
#define CHANGE(NAME) if(srcindex + strlen(NAME) > length){\
				    strcpy((char*)&dest[destindex], (char*)&src[srcindex]);\
				    destindex += strlen((char*)&src[srcindex])+1;\
				    srcindex = length;\
			    }else {\
			    	temp = src[srcindex+strlen(NAME)];\
			    	src[srcindex+strlen(NAME)] = '\0';\
			    	if( strcmp( (char*)&src[srcindex], NAME ) == 0 ){\
			    		dest[destindex] = Num_##NAME+'0';\
			    		destindex++;\
			    		srcindex += strlen(NAME);\
			    	    src[srcindex] = temp;\
			    	}else {\
			    		dest[destindex] = src[srcindex];\
			    	    src[srcindex+strlen(NAME)] = temp;\
			    		srcindex++;\
			    	}			    		\
			    }

void main(){
	char src[1000] = "( Beta, ( Gamma, ( Delta , Epsilon ) ), Alpha )";
	char *t1 = NULL;
	char dest[1000] = {0};
	int srcindex = 0;// index of src
	int destindex = 0;// index of dest
	int length = strlen(src);
	char temp;
	while(srcindex < length){
		switch(src[srcindex]){
			case 'B':
				CHANGE(Beta)
				break;
			case 'G':
				CHANGE(Gamma)
				break;
			case 'D':
				CHANGE(Delta)
				break;
			case 'E':
				CHANGE(Epsilon)
				break;
			case 'A':
				CHANGE(Alpha)
				break;
			default:
				dest[destindex] = src[srcindex];
			    destindex++;
			    srcindex++;
		}
	}
	dest[destindex] = '\0';
	printf("The dest is : %s\n" ,dest);
	system("pause");
}