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#ifndef TNT_ARRAY2D_UTILS_H
#define TNT_ARRAY2D_UTILS_H
#include <cstdlib>
#include <cassert>
namespace TNT
{
/**
Write an array to a character outstream. Output format is one that can
be read back in via the in-stream operator: two integers
denoting the array dimensions (m x n), followed by m
lines of n elements.
*/
template <class T>
std::ostream& operator<<(std::ostream &s, const Array2D<T> &A)
{
int M=A.dim1();
int N=A.dim2();
s << M << " " << N << "\n";
for (int i=0; i<M; i++)
{
for (int j=0; j<N; j++)
{
s << A[i][j] << " ";
}
s << "\n";
}
return s;
}
/**
Read an array from a character stream. Input format
is two integers, denoting the dimensions (m x n), followed
by m*n whitespace-separated elments in "row-major" order
(i.e. right-most dimension varying fastest.) Newlines
are ignored.
<p>
Note: the array being read into references new memory
storage. If the intent is to fill an existing conformant
array, use <code> cin >> B; A.inject(B) ); </code>
instead or read the elements in one-a-time by hand.
@param s the charater to read from (typically <code>std::in</code>)
@param A the array to read into.
*/
template <class T>
std::istream& operator>>(std::istream &s, Array2D<T> &A)
{
int M, N;
s >> M >> N;
Array2D<T> B(M,N);
for (int i=0; i<M; i++)
for (int j=0; j<N; j++)
{
s >> B[i][j];
}
A = B;
return s;
}
/**
Matrix Multiply: compute C = A*B, where C[i][j]
is the dot-product of row i of A and column j of B.
@param A an (m x n) array
@param B an (n x k) array
@return the (m x k) array A*B, or a null array (0x0)
if the matrices are non-conformant (i.e. the number
of columns of A are different than the number of rows of B.)
*/
template <class T>
Array2D<T> matmult(const Array2D<T> &A, const Array2D<T> &B)
{
if (A.dim2() != B.dim1())
return Array2D<T>();
int M = A.dim1();
int N = A.dim2();
int K = B.dim2();
Array2D<T> C(M,K);
for (int i=0; i<M; i++)
for (int j=0; j<K; j++)
{
T sum = 0;
for (int k=0; k<N; k++)
sum += A[i][k] * B [k][j];
C[i][j] = sum;
}
return C;
}
} // namespace TNT
#endif
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