1.7E +/- 308 (15 digits)
这是 MSDN 给出的 DOUBLE 的极值。
至于 FLT_EPSILON,看看 MSDN 解释它存在的原因:
Floating-point decimal values generally do not have an exact binary representation. This is a side effect of how the CPU represents floating point data. For this reason, you may experience some loss of precision, and some floating-point operations may produce unexpected results.
。。。
To resolve the behavior, most programmers either ensure that the value is greater or less than what is needed
。。。
These constants (指 FLT_EPSILON 和 DBL_EPSILON )are defined as the smallest positive number x, such that x+1.0 is not equal to 1.0.