变量转换
浮点数转成整数
- round:四舍五入
IDL>print,round(5.1),round(5.9) IDL> 5, 6
- ceil:向上进
IDL>print,round(5.1),round(5.9) IDL> 6, 6
- floor:截取整数
IDL>print,round(5.1),round(5.9) IDL> 5, 5
- 整数范围很小（long），要转换大的整数，加上/L64
- astro_lib中的nint程序，可以代替round，而且
- (1) if no absolute value exceeds 32767, then the array is returned as
as a type INTEGER instead of LONG
- (2) NINT will work on strings, e.g. print,nint(['3.4','-0.9']) will
give [3,-1], whereas ROUND() gives an error message