Implicit conversion to array index type

Question

Let's say I have following type:

struct XY
{
  short nIndex;
  
  constexpr operator int()
  {
     return nIndex;
  }
};

What can I change to make the following work:

char arr[10][255];

constexpr XY xy{1};

char *x = arr[xy];

I thought that just giving XY a convert-to-int operator would be enough but I'm getting the error:

no match for 'operator[]' (operand types are 'const char [10][255]' and 'const XY')

Sorry, but I couldn't resist: Is this a case of The XY Problem? 😊‎ — Adrian Mole
– Adrian Mole, Commented Dec 20, 2020 at 21:37

eerorika · Accepted Answer · 2020-12-20 21:35:01Z

4

Since the variable is constexpr, you cannot call the conversion operator that is not const-qualified. Solution is simple: Make the conversion operator const qualified:

constexpr operator int() const

answered Dec 20, 2020 at 21:35

eerorika

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1 Comment

Jimmy R.T. Over a year ago

Didn't expect the problem to be solved as simply. It worked. Thanks.

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