最有用的用户取得C-宏（海合会，也C99）？ [英] The most useful user-made C-macros (in GCC, also C99)?

问题描述

什么 C 宏是在你看来是最有用的？我发现下面的之一，我用做向量运算在 C

 的#define v3_op_v3（X，OP，Y，Z）{Z [0] = X [0] OP Y [0]; \\
                               Z [1] = X [1]的运算Y [1]; \\
                               Z [2] = X [2]的运算Y [2];}
 

它的工作原理类似的：

  v3_op_v3（vectorA，+，vectorB，vectorC）;
v3_op_v3（vectorE，*，vectorF，vectorJ）;
...
 

解决方案

有关，每个C99循环：

 ＃定义的foreach（项目，数组）\\
    对于（INT保持= 1，\\
            计数= 0，\\
            大小= sizeof的（阵列）/ *的sizeof（数组）; \\
        保持和放大器;＆安培;数=大小！; \\
        保持=！不断，算上++）\\
      对于（项目=（阵列）+计数;保持;！=守守）诠释主（）{
  诠释一个[] = {1，2，3};
  INT总和= 0;
  的foreach（INT常量* C，A）
    总和+ = * C;
  的printf（总和=％d个\\ N，总和）;  //多维数组
  INT A1 [] [2] = {{1,2}，{3,4}};
  的foreach（中间体（* C1）[2]，a1）中
    的foreach（INT * C2，C1 *）
      的printf（C2 =％d个\\ N，* C2）;
}
 

What C macro is in your opinion is the most useful? I have found the following one, which I use to do vector arithmetic in C:

#define v3_op_v3(x, op, y, z) {z[0]=x[0] op y[0]; \
                               z[1]=x[1] op y[1]; \
                               z[2]=x[2] op y[2];}

It works like that:

v3_op_v3(vectorA, +, vectorB, vectorC);
v3_op_v3(vectorE, *, vectorF, vectorJ);
...

解决方案

for-each loop in C99:

#define foreach(item, array) \
    for(int keep=1, \
            count=0,\
            size=sizeof (array)/sizeof *(array); \
        keep && count != size; \
        keep = !keep, count++) \
      for(item = (array)+count; keep; keep = !keep)

int main() {
  int a[] = { 1, 2, 3 };
  int sum = 0;
  foreach(int const* c, a)
    sum += *c;
  printf("sum = %d\n", sum);

  // multi-dim array
  int a1[][2] = { { 1, 2 }, { 3, 4 } };
  foreach(int (*c1)[2], a1)
    foreach(int *c2, *c1) 
      printf("c2 = %d\n", *c2);
}

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