I'm using the LXLE 14.04 distribution of Linux. I want to write a C program to read commands, interpret and perform them. I'd like the program to be efficient, and I do not want to use a linked list. The commands are operations on sets. Each set can contain any of the values from 0 through 127 inclusive. I decided to represent a set as an array of characters, containing 128 bits. If bit at position pos is turned on then the number pos is in the set and if the bit at position pos is turned off then the number pos is not present in the set. For example, if the bit at position 4 is 1, then the number 4 is present in the set, if the bit at position 11 is 1 then the number 11 is present in the set.
The program should read commands and interpret them in a certain way. There are a few commands: read_set, print_set, union_set, intersect_set, sub_set and halt.
For example, the command read_set A,1,2,14,-1 in the terminal will cause the reading of values of the list into the specified set in the command. In this case the specified set in the command is A. The end of the list is represented by -1. So after writing this command, the set A will contain the elements 1,2,14.
This is what I have so far. Below is the file set.h
#include <stdio.h>
typedef struct
{
char array[16]; /*Takes 128 bits of storage*/
}set;
extern set A , B , C , D , E , F;
This is the file main.c
#include <stdio.h>
#include "set.h"
#include <string.h>
#include <stdlib.h>
set A , B , C , D , E , F; /*Variable definition*/
set sets[6];
/*Below I want to initialize sets so that set[0] = A set[1] = B etc*/
sets[0].array = A.array;
sets[1].array = B.array;
sets[2].array = C.array;
sets[3].array = D.array;
sets[4].array = E.array;
sets[5].array = F.array;
void read_set(set s,char all_command[])
{
int i, number = 0 , pos;
char* str_num = strtok(NULL,"A, ");
unsigned int flag = 1;
printf("I am in the function read_set right now\n");
while(str_num != NULL) /*without str_num != NULL get segmentation fault*/
{
number = atoi(str_num);
if(number == -1)
return;
printf("number%d ",number);
printf("str_num %c\n",*str_num);
i = number/8; /*Array index*/
pos = number%8; /*bit position*/
flag = flag << pos;
s.array[i] = s.array[i] | flag;
str_num = strtok(NULL, ", ");
if(s.array[i] & flag)
printf("Bit at position %d is turned on\n",pos);
else
printf("Bit at position %d is turned off\n",pos);
flag = 1;
}
}
typedef struct
{
char *command;
void (*func)(set,char*);
} entry;
entry chart[] = { {"read_set",&read_set} };
void (*getFunc(char *comm) ) (set,char*)
{
int i;
for(i=0; i<2; i++)
{
if( strcmp(chart[i].command,comm) == 0)
return chart[i].func;
}
return NULL;
}
int main()
{
#define PER_CMD 256
char all_comm[PER_CMD];
void (*ptr_one)(set,char*) = NULL;
char* comm; char* letter;
while( (strcmp(all_comm,"halt") != 0 ) & (all_comm != NULL))
{
printf("Please enter a command");
gets(all_comm);
comm = strtok(all_comm,", ");
ptr_one = getFunc(comm);
letter = strtok(NULL,",");
ptr_one(sets[*letter-'A'],all_comm);
all_comm[0] = '\0';
letter[0] = '\0';
}
return 0;
}
I defined a command structure called chart that has a command name and function pointer for each command. Then I have created an array of these structures which can be matched within a loop.
In the main function, I've created a pointer called ptr_one. ptr_one holds the value of the proper function depending on the command entered by the user. The problem is, that since user decides which set to use,I need to represent the sets as some variable, so that different sets can be sent to the function ptr_one. I thought about creating an array in main.c like so
set sets[6];
sets[0] = A;
sets[1] = B;
sets[2] = C;
sets[3] = D;
sets[4] = E;
sets[5] = F;
And then call the function ptr_one in the main function like this ptr_one(sets[*letter-'A'] , all_command). That way, I convert my character into a set.
The problem is that while writing the above code I got the following compile error:
error: expected ���=���, ���,���, ���;���, ���asm��� or ���attribute��� before ���.��� token
I also tried the following in the file main.c
sets[0].array = A.array;
sets[1].array = B.array;
sets[2].array = C.array;
sets[3].array = D.array;
sets[4].array = E.array;
sets[5].array = F.array;
But I got this compile error expected ���=���, ���,���, ���;���, ���asm��� or ���attribute��� before ���.��� token
I know similar questions have been asked, by they don't seem to help in my specific case. I tired this set sets[6] = { {A.array},{B.array},{C.array},{D.array},{E.array},{F.array} } too but it did not compile.
What's my mistake and how can I initialize sets so that it holds the sets A though F?