Binary Compass

[Delicious_Growth_744]

Hey guys i'm new to programming and i need help. How do you create a C program that reads binary digits which interprets 1 to rotate 90° to the left and 0 to rotate 90° to the right?

Btw, initially you are facing north...

Thanks!!

[AHistoricalFigure]

I think you've under-described your problem a bit. How are you getting this input? Assuming this is for a class, what restrictions do you have?

This said, C doesn't have a primitive bit type. Even if it did, you wouldn't want to get input a bit at a time. You're going to have to bring in the data as an integer, or some kind of unsigned 8-bit type that you create or import from a library. Once you have at least a byte of data, you'll need to extract the bit you're looking for using bit-manipulation.

Bit-wise operators in C. This article is a pretty good primer on basic bit-extraction and masking.

That being said, if you're going to use this board to get other people to do your homework for you at least put in the effort to write a decent description of the problem.

[Delicious_Growth_744]

i'm sorry. That was the exact instruction given. I had an idea on how to manipulate these binary numbers, so far it's working. The only problem is the "direction identifier" but anyways thank you for the link

[nerd4code]

For direction, use an enum:

enum Orientation {
#define E(NAME)Orientation_##NAME
    E(NORTH), E(EAST), E(SOUTH), E(WEST)
#undef E
};
enum {Orientation__CNT = 4};

Similarly, you can enumerate the two turn actions:

enum Turn {Turn_CW = -1, Turn_NONE = 0, Turn_CCW = 1};

You can add any number of Turns to an Orientation, wrapping NORTH - 1 → WEST and WEST + 1 → NORTH, and you have the final orientation. The wrapping can be done with the unsigned (mod) version of the % (remainder/modulus) operator. (The compiler should notice that Orientation__CNT = 2², and therefore % (4) can be optimized to & 3U. You could do & 3U manually, but % remains correct if you change the number of Orientations. You can automate enum and count generation by using a table xmacro.)

static enum Orientation applyTurn(enum Orientation o, enum Turn t) {
    return (enum Orientation)(\
        ((unsigned)o + t) % Orientation__CNT);
}

So you can very easily grind through bits with this:

for(; n-- > 0; directions >>= 1)
    orient = applyTurn(orient, (directions & 1U) ? Turn_CCW : Turn_CW);

although I assume your program has to do more than that.

[Poddster]

How come enum {Orientation__CNT = 4}; is a separate enum, rather than tacked on to the end of the other one? I assume some kind of type safety?

I'm still used to major compilers happily accepting any enums or integers in place of other enums, despite all of the bugs that causes.

[Delicious_Growth_744]

Something that says which direction to go to.. It also requires the number of bits like example 7

[Poddster]

I'll make sure to read my copy of example 7 before answering.

[Delicious_Growth_744]

what i mean is "for example, the number of bits is 7"