NullaryFunctionExpression.h

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// ========================================================================= //
// This file is part of MyraMath, copyright (c) 2014-2019 by Ryan A Chilton  //
// and distributed by MyraCore, LLC. See LICENSE.txt for license terms.      //
// ========================================================================= //

#ifndef MYRAMATH_EXPRESSION_NULLARYFUNCTIONEXPRESSION_H
#define MYRAMATH_EXPRESSION_NULLARYFUNCTIONEXPRESSION_H

#include <myramath/expression/ExpressionBase.h>
#include <myramath/expression/Index2string.h>

#include <myramath/utility/eprintf.h>

namespace myra {
namespace detail {

// Implementation detail, an Expression that takes zero arguments.
template<class Function,int Arity> class NullaryFunctionExpression : public ExpressionBase<Arity,typename Function::Output>
  {
  public:

    // Reflect types from underlying Function.
    typedef typename Function::Output Output;

    // Constructor, requires Function f and input Expression's (A,B,C).
    NullaryFunctionExpression(const Function& in_f, Index<Arity> in_fsize)
      : f(in_f), fsize(in_fsize) { }

  protected:

    // Size inspector.
    virtual Index<Arity> size() const
      { return fsize; }
  
    // Given an Index i, returns f()
    virtual Output evaluate(Index<Arity> i) const
      { return f.evaluate(); }

    // Virtual copy constructor.
    virtual ExpressionBase<Arity,Output>* clone() const
      { return new NullaryFunctionExpression<Function,Arity>(f,fsize); }

  private:

    // Underlying Function instance.
    Function f;
    
    // Underlying size.
    Index<Arity> fsize;
  };

// Helper factory function, returns f().
template<class Function, int Arity>
NullaryFunctionExpression<Function,Arity>
make_NullaryFunctionExpression(const Function& f, Index<Arity> size)
  { return NullaryFunctionExpression<Function,Arity>(f,size); }

} // namespace detail

} // namespace myra

#endif