enumerated type and lvalue missing

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

Code:

---

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

---

where TerrainType is enumerated type

Code:

---

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.

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

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.

Quote:

---

Originally Posted by 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.

---

And what compiler should do with things like

Code:

---

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

---

???

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

Code:

---

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>

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

Code:

---

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

Code:

---

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:

Code:

---

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

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

---

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.

Code:

---

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