function Trunc(X: Extended): Int64;DescriptionThe Trunc function truncates a real-type value to an integer-type value. X is a real-type expression. Trunc returns an Int64 value that is the value of X rounded toward zero.If the truncated value of X is not within the Int64 range, an EInvalidOp exception is raised.
ceil () 望大的整数取整 如 2.13 -> 3 , -2.13 -> -2
floor () 与上相反