What's the difference between scalbn and ldexp

Question

The C99 standard defines ldexp(double a, int exp) as a × 2 ^exp and scalbn(double a, int exp) as a × FLT_RADIX ^exp

What's the difference between the two if I'm using IEEE-754 arithmetic (ie FLT_RADIX == 2)?

Answer 1

Appendix F:

F.9.3.6  The ldexp functions

       [#1] On a binary system, ldexp(x, exp) is equivalent to

               scalbn(x, exp)

Answer 2

FLT_RADIX == 2时没有区别。