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Programming in C Chapter 10 The Preprocessor

Programming in C Chapter 10 The Preprocessor. # include “filename” # include <filename>. The Use of #include. file2.c. # include “file2.c”. B. A. A. file2.c. file1.c. file1.c. The Use of #include(cont.). file3.c. file2.c. file1.c. A. # include “file2.c”.

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Programming in C Chapter 10 The Preprocessor

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  1. Programming in CChapter 10 The Preprocessor

  2. #include “filename” #include <filename> The Use of #include file2.c #include “file2.c” B A A file2.c file1.c file1.c

  3. The Use of #include(cont.) file3.c file2.c file1.c A #include “file2.c” #include “file3.c” C A B file3.c file1.c file2.c

  4. Example /* powers.h */ #define sqr(x) ((x)*(x)) #define cube(x) ((x)*(x)*(x)) #define quad(x) ((x)*(x)*(x)*(x)) /*ch8_10.c*/ #include <stdio.h> #include "d:\fengyi\bkc\powers.h" #define MAX_POWER 10 void main() { int n; printf("number\t exp2\t exp3\t exp4\n"); printf("----\t----\t-----\t------\n"); for(n=1;n<=MAX_POWER;n++) printf("%2d\t %3d\t %4d\t %5d\n",n,sqr(n),cube(n),quad(n)); }

  5. #define identifier token_stringopt The Use of #define 例 #define WIDTH 80 #define LENGTHWIDTH+40 var=LENGTH*2; Means: var= 80+40 *2; #define YES 1 main() { …….. } #undef YES #define YES 0 max() {…….. } ( ) YES Previous Scope ( ) YES New scope #define YES 1 #define NO 0 #define PI 3.1415926 #define OUT printf(“Hello,World”); #define WIDTH 80 #define LENGTHWIDTH+40 var=LENGTH*2; Means: var= 80+40 *2; if(x==YES) printf(“correct!\n”); else if (x==NO) printf(“error!\n”); Means： if(x==1) printf(“correct!\n”); else if (x==0) printf(“error!\n”); #define PI 3.14159 printf(“2*PI=%f\n”,PI*2); Means: printf(“2*PI=%f\n”,3.14159*2); #define MAX MAX+10 ()

  6. #define identifier(identifier,…, identifier)token_stringopt #define with Arguments • #define S(a,b) a*b • ……….. • area=S(3,2); • means： area=3*2; #define POWER(x) x*x x=4; y=6; z=POWER(x+y); means：z=x+y*x+y; simple： #define POWER(x) ((x)*(x)) means： z=((x+y)*(x+y));

  7. #define MAX(x,y) (x)>(y)?(x):(y) ……. main() { int a,b,c,d,t; ……. t=MAX(a+b,c+d); …… } Equal：t=(a+b)>(c+d)?(a+b):(c+d); int max(int x,int y) { return(x>y?x:y); } main() { int a,b,c,d,t; ……. t=max(a+b,c+d); ……… }

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