Appending a Vector to a Vector

[natekelsey]

Ok I know this is pretty basic but I can't seem to understand why this isn't working.
This is my test code:

test_(b2.to_string() == "01010100");
b2.erase(3);   // Having an issue inside erase function
test_(b2.to_string() == "0100100");

This is my erase function:

void erase(size_t pos, size_t nbits = 1) {
		BitArray<> front = slice(0, pos);
		BitArray<> back = slice(pos + nbits, (used_bits - (pos + nbits)));
		front += back;
		cout << front << endl;	//Test purposes: output is 0100 which is incorrect
		*this = front;
}

So is there something I'm forgetting here? By my understanding it should append 'back' to the end of 'front'. Thank you for helping me with this.

[ne555]

¿are we suppossed to guess the implementation details of your class?

You say that `+=' should append but it does not, perhaps the problem is with its code.
Or perhaps it isn't receiving the right arguments, so blame `slice()' or your usage of it
Or the problem may be in your print algorithm.


Provide enough code to reproduce your problem.

[natekelsey]

This is my slice()

BitArray slice(size_t pos, size_t count)const {
		BitArray<> b(count);
		for (int i = 0; i < count; i++)
		{
			b.assignBit(i, this->readBit(i + pos));
		}
		return b;
	}

This is my to_string()

	string to_string() const {
		string charStr = "";
		for (size_t i = 0; i < used_bits; i++) {
			if (test(i))
				charStr += '1';
			else
				charStr += '0';
		}
		return charStr;
	}

This is my test() considering it's being called in my to_string()

bool test(size_t pos)const {
		if (Bit_Vector.size() == 0)
			throw logic_error("Empty");
		else
			return Bit_Vector[pos / BITS_PER_WORD] & (1u << (pos%BITS_PER_WORD));
	}

[natekelsey]

--Edited
Apparently line 4 of my second block of code in my first post:

front+=back;

is calling on this function

// Appends a BitArray Object
BitArray& operator+=(const BitArray& b)
	{
		if (capacity() == used_bits)
			Bit_Vector.resize(Bit_Vector.size() + Bit_Vector.size());
		for (size_t i = 0; i < used_bits; ++i) {
			copy(used_bits - 1, b[i]);
		}
		used_bits++;
		return *this;
	}

[ne555]

http://www.eelis.net/iso-c++/testcase.xhtml

A testcase consisting of randomly copy&paste'd bits of code that you thought were relevant can obviously not reproduce the problem.

// Appends a BitArray Object
BitArray& operator+=(const BitArray& b)
	{
		if (capacity() == used_bits) //¿you don't need to consider `b'?
			Bit_Vector.resize(Bit_Vector.size() + Bit_Vector.size()); //¿is this enough? ¿what if `b' is really big?
		for (size_t i = 0; i < used_bits; ++i) { //in the next line you are traversing `b', so b.used_bits
			copy(used_bits - 1, b[i]); //no idea what does this function do, ¿why the first argument remains constant?
		}
		used_bits++; //¿so you just added only one bit?
		return *this;
	}

[natekelsey]

I'm trying to add the value of b, which in this case is '0100', to *this, which is the value of '010'. My end result is suppose to be '0100100' but I'm getting '0100' instead.

[ne555]

¿why is it so hard for you to provide your full code?


add b, which in this case is '0100', (4 bits)
to *this, which is the value of '010'. (3 bits)
result is suppose to be '0100100' (7 bits)
but I'm getting '0100' (4 bits)

I'm going to suppose that `used_bits' is the quantity of bits that you've got. (so this->used_bits is 3 and b.used_bits is 4)

In your code you do used_bits++; increasing in just 1 unit, but you need to increase it in 4
used_bits += b.used_bits; (however this invariance should be handled by your insert_at_the_end() function, which you've called copy())

In the loop you do for (size_t i = 0; i < used_bits/*3*/; ++i) when trying to add the bits of `b', you'll miss the last one.