EvalNumericalGradient accepts four arguments, the h represents a small change in input and it can be either positive or negative.

MatBroadcast is analogous to the NumPy array broadcasting.

NewAffineSigmoid accepts three parameters, inDim (input dimension), and outDim (output dimension).

SumAlongColumn accepts a matrix and perform summing along each column of the matrix.

Any function that accepts a Dense matrix and returns a Dense matrix will satisfy the definition of a ForwardProp.