小编Die*_*rin的帖子

如果我跑:

>>> import math
>>> print(math.pi)
3.141592653589793

然后pi打印16位数,

但是,根据:

>>> import sys
>>> sys.float_info.dig 
15

我的精度是15位数.

那么,我应该依赖该值的最后一位(即π的值确实是3.141592653589793nnnnnn).

objectid()Julia 中的、hash()、pointer()和有什么区别pointer_from_objref()？

与 进行比较的运算符是什么===？

julia> L1 = [1,2,3];

julia> L2 = L1;

julia> L3 = copy(L1);

julia> objectid(L1), objectid(L2), objectid(L3)
(0xac55c2b098913d98, 0xac55c2b098913d98, 0xbdee7946bbc068f0)

julia> hash(L1), hash(L2), hash(L3)
(0xecc5186e7be222c6, 0xecc5186e7be222c6, 0xecc5186e7be222c6)

julia> pointer_from_objref(L1), pointer_from_objref(L2), pointer_from_objref(L3)
(Ptr{Nothing} @0x00007f6888141e40, Ptr{Nothing} @0x00007f6888141e40, Ptr{Nothing} @0x00007f68881438f0)

julia> pointer(L1), pointer(L2), pointer(L3)
(Ptr{Int64} @0x00007f6888141e80, Ptr{Int64} @0x00007f6888141e80, Ptr{Int64} @0x00007f6888143930)

从文档中：

objectid(x)                                                                                
Get a hash value for x based on object identity. objectid(x)==objectid(y) if x === y.      

hash(x[, h::UInt])                                                                         
Compute an …