是否可以通过 C 中的预处理器指令计算斐波那契数列？

Question

Just for personal study and better understanding of C code preprocessor:

I am wondering if it is possible to implement Fibonacci function by preprocessor directives in C language.

Normal definition of Fibonacci function could be:

int f(int i) {  // i should be non-negative integer
    if (i <= 1) {
        return 1;
    }
    return f(i - 1) + f(i - 2);
}

The approach of using the template metaprogramming technique in C++ is not what I need.

---

It seems that it is not possible to perform recursive calculations by using the code preprocessor?

Answer 1

I do not think macro in C can support recursive macro. But Fibonacci is possible macro. By using the fomular of nth number

#define Fibonacci(n) (POW(1+POW(5,1/2),n) - POW(1-POW(5,1/2),n))/POW(5,1/2)

Answer 2

Recursive macros are not allowed in C or in C++.

Macros — just a text replacement, not computation

Answer 3

Using boost preprocessor's slots, and an iterative solution, with the macro I as input:

#ifndef INITIALIZE
#define INITIALIZE
# include <boost/preprocessor/slot.hpp>
# if I<=2
1
# else
#  define BOOST_PP_VALUE 2
#  include BOOST_PP_ASSIGN_SLOT(1)
#  define BOOST_PP_VALUE 1
#  include BOOST_PP_ASSIGN_SLOT(3)
#  define BOOST_PP_VALUE 1
#  include BOOST_PP_ASSIGN_SLOT(4)
#  include __FILE__
# endif
#else
#  define BOOST_PP_VALUE BOOST_PP_SLOT(1) + 1
#  include BOOST_PP_ASSIGN_SLOT(1)
#  define BOOST_PP_VALUE BOOST_PP_SLOT(3)
#  include BOOST_PP_ASSIGN_SLOT(2)
#  define BOOST_PP_VALUE BOOST_PP_SLOT(4)
#  include BOOST_PP_ASSIGN_SLOT(3)
#  define BOOST_PP_VALUE BOOST_PP_SLOT(2) + BOOST_PP_SLOT(3)
#  include BOOST_PP_ASSIGN_SLOT(4)
# if I==BOOST_PP_SLOT(1)
BOOST_PP_SLOT(4)
# else
#  include __FILE__
# endif
#endif

Demo: http://coliru.stacked-crooked.com/a/c399d11dedc306ca