enumerated type and lvalue missing

[baniakjr]

I've writen some program in borland C++ builder X the want to compile it in builder 6 and VS C++ 2005 and i've got such problem in both compilers i get such error

"error C2676: binary '++' : 'TerrainType' does not define this operator or a conversion to a type acceptable to the predefined operator" in VS

and

"[C++ Error] Modedit.cpp(33): E2277 Lvalue required" in C++ Builder 6

for this part of code

for (TerrainType terrain=Plains;terrain<=Village;terrain++)

where TerrainType is enumerated type

enum TerrainType
{
  Plains=0,
  Forest,
  Hills,
  Swamp,
  Water,
  Village
};

so how to make this loop work properly i've tried "+1" instead of "++" but then VS still shows errors and Builder compiles but program starts an infinit loop.

[Daved]

Unfortunately you cannot increment an enum. Try using an int instead as the type for terrain.

[baniakjr]

Hmmm.Ok i'll use int. Funny thing is that borland C++ builder X is compiling it and C++ builder 6 not. I've also found somebooks and tutorial that says it's correct code.That's why i'm puzzeld.

[vart]

Hmmm.Ok i'll use int. Funny thing is that borland C++ builder X is compiling it and C++ builder 6 not. I've also found somebooks and tutorial that says it's correct code.That's why i'm puzzeld.

And what compiler should do with things like

enum flags
{
  red = 1,
  blue = 2,
  green = 4,
  black=8,
 ...
}

???

[Salem]

By some means, you should be able to overload the ++ operator for the enum, so that any horrid casting is well hidden from normal users.

Consider this

enum TerrainType
{
  Plains=0,
  Forest = 0,
  Hills = -42,
  Swamp = 666,
  Water = 8,
  Village = 1000
};

Naive casting of ++ is going to produce illegal enum values.
enums are allowed to have disjointed sequences and identical values for different symbols, which is why you don't get an automatic ++ operator.

<edit: beaten>

[baniakjr]

I see the point. Thats true. But still i've tried that in borland C++ builder X and when i tried to enumerat lik this

enum TerrainType
{
  Plains=0,
  Forest = 0,
  Hills = -42,
  Swamp = 666,
  Water = 8,
  Village = 1000
};

i've got error but not in enumeration but in loops using it.

and i've tried

enum flags
{
  red = 1,
  blue = 2,
  green = 4,
  black=8
}

than it's perfectly compiling it just like puting them in rising order according to value and than make correct step. Maybe builder X have some modified iostream library with overloaded ++ operator.

In any case thanks for help.no i see why it didn't work in VS and builder 6. And it sounds resonable And i wonder if i should use it or no in builder X nevertheless it's compiling and working correct.

p.s. I've also found a book in which i saw it. It's "C++ Pocket Refrence" published by O'Reilly.

there is such code sample:

enum SpectrumColor
{
    Red,Orange,Yellow,Green,Blue,Indigo,Violet
};

for (SpectrumColor s=Red;s<=Violet;s++)
{
   ...
}

[Mario F.]

If the enumerators are in sequence, it makes sense to use it inside a for, and you see no reason for the enumeration to become anything else in the future, do it.

Cast to int. Don't overload ++ though.

enum TerrainType
{
  Plains=0,
  Forest,
  Hills,
  Swamp,
  Water,
  Village,
  NUM_TERRAINTYPES
};

for (unsigned int i = Plains; i != NUM_TERRAINTYPES; ++i) {

}

If you see one reason whatsoever why maybe TerrainType will one day not be in sequence, then you shouldn't do this.

EDIT: Corrected ugly code error