layers/layer.hpp

#pragma once
#include "../core/tensor.hpp"
#include <vector>

namespace newnet {

// Abstract base class — every layer implements these two methods
class Layer {
public:
    virtual ~Layer() = default;
    
    // Forward: takes input tensor, returns output tensor
    virtual Tensor forward(const Tensor& input) = 0;
    
    // Backward: takes gradient from layer above, returns gradient to pass down
    virtual Tensor backward(const Tensor& grad_output) = 0;
    
    // Return all learnable parameters (weights, biases) for optimizer
    virtual std::vector<Tensor*> parameters() { return {}; }
};

} // namespace newnet