Misunderstanding of range-based for loop?

Question

A compiler error occurs when I try to compile the following code:

for(binary_instructions_t &inst: BinaryInstructions){


}

BinaryInstructions is this enum class:

typedef unsigned int binary_instructions_t;

enum class BinaryInstructions : binary_instructions_t
{
    END_OF_LAST_INSTR = 0x0,

    RESET,
    SETSTEP,
    START,
    STOP,

    ADD,
    REMOVE,
};

Should I be allowed to "do a" range based for loop using the items inside an enum class? Or have I subtly misunderstood in that range based for loops are for searching the contents of an array and not stuff like enum classes?

I have also tried: Creating an instance and searching within the instance:

BinaryInstructions bsInstance;
for(binary_instructions_t &inst : bsInstance){


}

But no cigar... Thanks in advance,

score 8 · Accepted Answer · edited May 23 '17 at 11:56

8

The range-based for loop needs a collection, like an array or a vector. The enum class isn't a collection.

However, it's C++, so there's a workaround. See: Allow for Range-Based For with enum classes?

edited May 23 '17 at 11:56

Community

1
1

answered Feb 19 '13 at 18:57

Seth

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that sweet! I love that implementation. Much cleaner than the casting to int solution I would have used. – David Hope Feb 19 '13 at 19:00

score 0 · Answer 2 · answered Feb 19 '13 at 19:01

Range-based for-loops are a mechanism for easy iteration over a list of elements. A 'list of elements' can be a plain array or an instance of a class that implements the beginand end methods returning an iterator type.

Example:

int arr[] = { 1, 2, 3, 4 };
for (int cur : arr)
   std::cout << cur << std::endl;

Misunderstanding of range-based for loop?

2 Answers2