signum文档中有一个小错误。
If d is ##Inf or ##-Inf => d
但是，(java.lang.Math/signum d)对于##Inf的输出是1.0，对于##-Inf的输出是-1.0。所以这行可能可以删除。
但是，如果应该显式地描述无穷大，那么
If d is ##Inf => 1.0
If d is ##-Inf => -1.0
next-down的文档是
Returns the adjacent double of d in the direction of ##-Inf.
If d is ##NaN => ##NaN
If d is ##Inf => ##-Inf
If d is zero => Double/MIN_VALUE
应该是
Returns the adjacent double of d in the direction of ##-Inf.
If d is ##NaN => ##NaN
If d is ##Inf => Double/MAX_VALUE
If d is zero => -Double/MIN_VALUE
round的文档是
Returns the closest long to a. If equally close to two values, return the one
closer to ##Inf.
If a is ##NaN => 0
If a is ##-Inf => ##-Inf
If a is ##Inf => ##Inf
应该是
Returns the closest long to a. If equally close to two values, return the one
closer to ##Inf.
If a is ##NaN => 0
If a is ##-Inf => Long/MAX_VALUE
If a is ##Inf => Long/MIN_VALUE
