问题描述
我想通过从终端通过用户获取类型变量来创建动态尺寸矩阵。这些类型将是整数，浮点型和双精度类型的矩阵。但是我在void类型中定义的函数和矩阵无法完成此工作，并且出现错误。我认为我的问题是无效的取消引用，但我无法解决。非常感谢您的帮助。
我从终端这样运行它
./run arg1 arg2 i arg4 ...
i = integer
f = float
d = double
我编写的函数如下
void ** random_matrice_gen(int row,int column,int upper,int lower,char * option){
void **matrice;
if(strcmp(option,"i") == 0){
matrice = malloc(row*sizeof(int *));
for(int i = 0 ; i < row ; i++){
matrice[i] = malloc( column*sizeof(int) );
}
}
else if(strcmp(option,"f") == 0){
matrice = malloc(row*sizeof(float *));
for(int i = 0 ; i < row ; i++){
matrice[i] = malloc( column*sizeof(float) );
}
} else {
matrice = malloc(row*sizeof(double *));
for(int i = 0 ; i < row ; i++){
matrice[i] = malloc( column*sizeof(double) );
}
}
srand((unsigned)time(0));
for(int i=0; i<row; i++){
for(int j=0; j<column; j++){
if(strncmp(option,"i",1) == 0){
int rand_num_i = ((int) rand() / RAND_MAX) * (int) ((upper- lower ) + lower);
matrice[i][j] = rand_num_i;
}
else if(strncmp(option,"f",1) == 0){
float rand_num_f = ((float) rand() / RAND_MAX) * (float)((upper- lower ) + lower);
printf("%f debug f\n",rand_num_f);
matrice[i][j] = rand_num_f;
} else {
double rand_num_d = ((double) rand() / RAND_MAX) * (double) ((upper- lower) + lower);
matrice[i][j] = rand_num_d;
}
}
}
return matrice;}
错误如下
'''50:15: warning: dereferencing ‘void *’ pointer
50 | matrice[i][j] = rand_num_i;
| ^
matrixgen.c:50:19: error: invalid use of void expression
50 | matrice[i][j] = rand_num_i;
| ^
matrisgen.c:57:15: warning: dereferencing ‘void *’ pointer
57 | matrice[i][j] = rand_num_f;
| ^
matrixgen.c:57:19: error: invalid use of void expression
57 | matrice[i][j] = rand_num_f;
| ^
matrixgen.c:61:15: warning: dereferencing ‘void *’ pointer
61 | matrice[i][j] = rand_num_d;
| ^
matrixgen.c:61:19: error: invalid use of void expression
61 | matrice[i][j] = rand_num_d;
'''
解决方法
（void *）是指向未知对象的指针，因此，大小未知，因此您无法对其进行指针算术。
您需要先进行投射，即
import re
results = []
matcher = re.compile(r'(\d) +outer \+$').search
with open('file.txt') as f:
for line in f:
match = matcher(line)
if match:
results.append(int(match.group(1)))
print(results)
可以编译。
,无法取消引用void *指针，并且matrice[i]就是这样的指针（并且数组索引等于指针取消引用）。
您需要将此指针转换为正确的类型：
((int *) matrice[i])[j] = rand_num_i;