范围操作员是否保证订购？

Question

Let's say , I am concatenating structs into an array with an append() call. Will the range operator during the read process guarantee the same order as elements were added to the array?

var array_of_structs []*some_struct_t
build_array(&array_of_structs)
for i,value := range array_of_structs {
    ..whatever, but I need `i` to be i=0,1,2... N in an ordered way
}

What do the specs say? I am going to calculate money, so I need to be sure it is ordered.

Answer 1

For a slice it is guaranteed by the spec

For an array, pointer to array, or slice value a, the index iteration values are produced in increasing order, starting at element index 0. If at most one iteration variable is present, the range loop produces iteration values from 0 up to len(a)-1 and does not index into the array or slice itself. For a nil slice, the number of iterations is 0.

Reference:

• https://golang.org/ref/spec#For_range