better way to scanf of a array of structs member?

Hi,

I have a matrix held in a text file, and I want it to go into a array of structs, but I can't seem to do it directly:
take my struct first.

Code:

---

struct xmatst { double ev; int ei;};
struct xmatst *in;

---

one of the simpler ones :-)

but. in order to get my values from my textfile into that ev member, I need to create another array of doubles called tmpin and do the usual:
f

Code:

---

or(i = 0; i < N; i++)
                for(j = 0; j < N; j++) {
                        fscanf(fp, "%lf", &tmpin[i*N+j]);

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And then I need to assign the tmpin values to my "real" array in. I tired to not use tmpin, and in the above assignment I used

Code:

---

in[i*N+j]->ev

---

but that gave me an "invalid type argument of ->" error, though I thought that was the way you referenced a pointer to a struct member.

May be the fact that it's an array of structs changes things. If I have to do things this way in C it'll be slower than perl. :-)

in is a pointer. in[i*n+j] is just a struct (in the same way that arrayname is a pointer*, but arrayname[25] is an int, or whatever).

*I mean that arrayname, by itself, will be turned into a pointer to the start of the array.

Edit: Oh, and why don't you just do fscanf(in, "%lf", &(in[i*N+j].ev)) in the first place? Or do you need to have a separate array of just the doubles?

I'm not sure how your file is formatted but if it's just rows of struct data separated by white space, I would do something like this:

Code:

---

for (i = 0; i<N; i++) {
  int rv = fscanf(fp, "&#37;f %d", &in[i].ev, &in[i].ei);
  if (rv < 2) {
    /** do something about the error **/
  }
}

---

This reads the file and should fill the rows in correctly as long as your matrix is in row major orientation.

Further reading.

eeek! thanks guys, very fast replies, and spot on too!

I'm still getting to know structs, and the -> identifier has me a bit confused.

I should have tried some c zen, and sat back, and just thought about the fundamentals.

however, sometime I betray and go to perl ... :-)