インテル® Fortran コンパイラー XE 13.1 ユーザー・リファレンス・ガイド
Elemental Module Intrinsic Function (Generic): Returns a floating-point value equal to the unbiased exponent of the argument. This is equivalent to the IEEE logb function.
The result type and kind is the same as x. The result has the value of the unbiased exponent of x if the value of x is not zero, infinity, or NaN. The value of the result is equal to EXPONENT(x) - 1.
If x is equal to 0, the result is -infinity if IEEE_SUPPORT_INF(x) is true; otherwise, -HUGE(x). In either case, the IEEE_DIVIDE_BY_ZERO exception is signaled.