Hi,
Thanks a lot for accepting my request to be a member of this group.
This is my first attempt at using MPIR, so please excuse me if you find
something silly :-)
I was looking for a way to convert very large decimals numbers into binary
using C. Since I did not find anything I thought of writing my own and
started exploring MPIR. There might be some easier alternatives but I am
using MPIR because I have to do some more maths on big numbers.
What I am trying to do is input a decimal number and then convert this into
binary. My program works fine till it find the number of bits required.
However something is wrong in the way I am using the operations in the
second last `for` loops, i.e:
kb[i] = b % 2;
b /= 2;
This is what I am trying to convert into MPIR specific operations using
mpz_mod() and mpz_cdiv_q(). What I have done is:
mpz_t d;
mpz_init (d);
mpz_set_str (d, "2" , 10); //because I want to find (something)mod2 , d
contains 2 now
for (int i = nob; i > 0; i--)
{
mpz_mod(kb[i], b, d); // kb[i] = b % 2
mpz_cdiv_q(b, b, d ); // b /= 2;
}
for (int i = nob; i > 0; i--)
{
cout<<kb[i]<<"\n";
}
This prints:
Please, enter the decimal value: 100
7
0
0
1
1
1
0
0
Press any key to continue . . .
Which is wrong. The correct is 01100100
Here is my code:
int main()
{
mpz_t b ;
size_t nob; //no. of bits will be here
mpz_init (b); //Initialize
char k[80]; //My decimal as an string will go here
cout << "Please, enter the decimal value: ";
cin.getline(k, sizeof k); //decimal value stored as string here
mpz_set_str (b, k , 10); //transfer the string into b, assuming base
10
nob = mpz_sizeinbase(b, 2); // find total number of bits in b
cout<<nob<<"\n";
mpz_t d;
mpz_init (d);
mpz_set_str (d, "2" , 10); //because I want to find (something)mod2
mpz_t kb[80000]; //Array. will store my converted binary bits in kb
for (int i = nob; i > 0; i--)
{
mpz_mod(kb[i], b, d); // implementing kb[i] = b % 2
mpz_cdiv_q(b, b, d ); // b /= 2;
}
for (int i = nob; i > 0; i--)
{
cout<<kb[i]<<"\n";
}
return 0;
}
Can someone help me solve this issue?
Thanks in advance for your valuable inputs.
Note: I did not know that the request will be accepted so quickly, so
posted it on stackoverflow also , which I can't delete now.
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