Thread: i have operator - error

i have practice CBigInt, but it dont run in operator -, when it down - up, can you help me? thanks .

Code:

#include "BigInt.h"
#include "iostream"
#include "string"
using namespace std;
BigInt::BigInt(){

	for(int i=0;i<N;i++){
		buffer[i]=0;
	}
}
//
istream &operator >>(istream &inp,BigInt &num){
	inp >>num.buffer;
	num.Format();
	return inp;
}
//
ostream &operator <<(ostream &out,BigInt &num){
	//out<<num.buffer;
	for(int i=0;i<N;i++){
		cout<<(int)num.buffer[i];
	}
	return out;

}


void BigInt::Format(){
	int len=strlen(buffer);
	for(int i=1;i<=len;i++){
		buffer[N-i]=buffer[len-i];//go to end array
	}
	for(int i=N-len-1;i>=0;i--){//convert all var still ->0;
		buffer[i]='0';
	}
	for(int i=0;i<N;i++){
		buffer[i]-=48;
	}
}
//
BigInt &BigInt::operator =(BigInt &num){
	for(int i=0;i<N;i++){
		buffer[i]=num.buffer[i];
	}
	return *this;
}
//
BigInt BigInt::operator +(BigInt &num){
	BigInt C;
	int mem=0;
	for(int i=N-1;i>=0;i--){
		C.buffer[i]=buffer[i]+num.buffer[i]+mem;
		if(C.buffer[i]>10){
			C.buffer[i]-=10;
			mem=1;
		}
		else mem=0;
	
	}
	return C;
}

BigInt BigInt::operator -(BigInt &num){
	BigInt h;int mem=0;
	if(len>=num.len){
	for(int i=N-1;i>=0;i--){
		h.buffer[i]=buffer[i]-num.buffer[i]-mem;
		if(buffer[i]>=num.buffer[i]){
			h.buffer[i]=buffer[i]-(num.buffer[i]+mem);
			mem=0;
		}
		if(buffer[i]<num.buffer[i])
		{
			h.buffer[i]=(buffer[i]+10)-num.buffer[i]-mem;
			mem=1;
		}
	
	}
	}
	if(len<num.len){
		for(int i=N-1;i>=0;i--){
		h.buffer[i]=num.buffer[i]-buffer[i]-mem;
		if(buffer[i]>=num.buffer[i]){
			h.buffer[i]=num.buffer[i]-(buffer[i]+mem);
			mem=0;
		}
		if(buffer[i]<num.buffer[i])
		{
			h.buffer[i]=(num.buffer[i]+10)-buffer[i]-mem;
			mem=1;
		}
	
		}
	}
	return h;
}

Code:

#include "iostream"
using namespace std;
#define N 10
class BigInt{
public :
	friend istream &operator >>(istream &inp,BigInt &num);
	friend	ostream &operator <<(ostream &out,BigInt &num);
	char buffer[N];
	BigInt();
	void Format();
	int len;
	BigInt &operator =(BigInt &num);
	BigInt operator +(BigInt &num);
	BigInt operator -(BigInt &num);
	

};

//

Code:

#include "iostream"
#include "BigInt.h"

using namespace std;
void main(){
	BigInt A;
	cout<<"Input A:";
	cin>>A;
	//cout<<A;
	BigInt B;
	//B=A;cout<<endl;
	cout<<"Input B:";
	cin>>B;

	BigInt C;
	//C=A+B;
	
	C=A-B;
	cout<<C;
	//BigInt K;
}

I'm not sure what you mean. Does it compile but not give the right answer?

You should look at your borrow -- you only check whether the top number is >= your bottom number without regard of whether there had been a borrow. Since you compute h.buffer before the check, just use that result -- if it's negative, borrow 10.

I'm not sure what you mean. Does it compile but not give the right answer?

You should look at your borrow -- you only check whether the top number is >= your bottom number without regard of whether there had been a borrow. Since you compute h.buffer before the check, just use that result -- if it's negative, borrow 10.

thanks but, i cann't performace operator - with down up if input number after > input number before

maybe you should try the google translator. it is very difficult to understand you.

We don't know how your class is designed -- you do exactly the same thing when the second number is bigger as when the first number is bigger. You will probably need to do something different, to deal with the fact that it is a negative number (unless you plan to store the number in 10's complement or something).

thanks for you

I have one operator *, it have run, but error logic, after input 2 BigInt, can u help me, instructor for me. thanks

Code:

#include "BigInt.h"
#include "iostream"
#include "string"
using namespace std;
BigInt::BigInt(){

	for(int i=0;i<N;i++){
		buffer[i]=0;
	}
}
//
istream &operator >>(istream &inp,BigInt &num){
	inp >>num.buffer;
	num.Format();
	return inp;
}
//
ostream &operator <<(ostream &out,BigInt &num){
	//out<<num.buffer;
	for(int i=0;i<N;i++){
		cout<<(int)num.buffer[i];
	}
	return out;

}


//int compare(char[] _m, BigInt _n){
	//if(_m.len>_n.len)
	//int len=strlen(buffer);

//
void BigInt::Format(){
	len=strlen(buffer);
	for(int i=1;i<=len;i++){
		buffer[N-i]=buffer[len-i];//go to end array
	}
	for(int i=N-len-1;i>=0;i--){//convert all var still ->0;
		buffer[i]='0';
	}
	for(int i=0;i<N;i++){
		buffer[i]-=48;
	}
}
//
int Compare(char *A, char *B) {
	// scan from left to right
	// which one bigger is bigger
	for (int i=0; i<N; i++) {
		if (A[i] >B[i])
			return 1;
		if (B[i] > A[i])
			return -1;
	}
	// otherwise, equal
	return 0;
}



//
BigInt &BigInt::operator =(BigInt &num){
	for(int i=0;i<N;i++){
		buffer[i]=num.buffer[i];
	}
	return *this;
}
//
BigInt BigInt::operator +(BigInt &num){
	BigInt C;
	int mem=0;
	for(int i=N-1;i>=0;i--){
		C.buffer[i]=buffer[i]+num.buffer[i]+mem;
		if(C.buffer[i]>10){
			C.buffer[i]-=10;
			mem=1;
		}
		else mem=0;
	
	}
	return C;
}



BigInt BigInt::operator *(BigInt &num){
	//int _Mul;
	int carry=0,count=0;
	BigInt MUL,SUM;
	if(Compare(buffer,num.buffer)==1){
		for(int j=0;j<num.len;j++){
			for(int i=N-1;i>=0;i--){
				MUL.buffer[i]=num.buffer[i]*buffer[i]+carry;
				if(MUL.buffer[i]>=10){
					MUL.buffer[i]=MUL.buffer[i]%10;
					carry=MUL.buffer[i]/10;
				}
				else
				{
					MUL.buffer[i]=MUL.buffer[i];
					carry=0;
				}
				count =j;

			}
			
		for (int k=0; k<count; k++)
				move(MUL.buffer);
			SUM=SUM+MUL;

		}
	}
	return SUM;
}
void BigInt::move(char* A){
	int k=N-strlen(A);
	for(int i=k;i<N-1;i++){
		A[i-1]=A[i];
		A[i]=0;
	}
}

Subtraction is just like adding a negative to a positive number, so why not just do it that way in the class? Addition works, doesn't it?

i like it simple, i have do function Subtraction.
but now i have problem operator *. can you help me?

You would have to tell us what the problem is for us to help you.

its operator *, multiplication, it have run, but errror logic, i dont know, it err where.

Code:

BigInt BigInt::operator *(BigInt &num){
	//int _Mul;
	int _y=0;
	int carry=0,count=0;
	BigInt MUL,SUM;
	if(Compare(buffer,num.buffer)==1){
		while(_y<N-num.len){
		for(int j=N-1;j>N-num.len;j--){
			for(int i=N-1;i>=N-len;i--){
				MUL.buffer[i]=num.buffer[j]*buffer[i]+carry;
				if(MUL.buffer[i]>=10){
					MUL.buffer[i]=MUL.buffer[i]%10;
					carry=MUL.buffer[i]/10;
				}
				else
				{
					//MUL.buffer[i]=MUL.buffer[i];
					carry=0;
				}
					count =j;
			}
		for (int k=0; k<_y; k++)
				move(MUL.buffer);
			SUM=SUM+MUL;
			_y++;
		}
	}
	}
	return SUM;
}
void BigInt::move(char* A){
	int k=N-strlen(A);
	for(int i=k;i<N-1;i++){
		A[i-1]=(int)A[i];
		A[i]=0;
	}
}