What enum got to do with it?

[correlcj]

Hello
I am having this error problem see comments below.
Can someone help me fix it, I am sure its simple but...
Like chess I do not move until i see it and right now i see nothing wrong?!?!


ERROR CODE:
C:\Program Files\Microsoft Visual Studio\MyProjects\enumerators\enumerator.cpp(73) : error C2676: binary '++' : 'enum month' does not define this operator or a conversion to a type acceptable to the predefined operator


HERE IS MY PROGRAM:
#include<stdio.h>

enum month {jan,feb,mar,apr,may,jun,jul,aug,sep,oct,nov,dec};
typedef enum month month;

month previous_month(month M)
{
switch (M)
{
case jan:
M=dec;break;
case feb:
M=jan;break;
case mar:
M=feb;break;
case apr:
M=mar;break;
case may:
M=apr;break;
case jun:
M=may;break;
case jul:
M=jun;break;
case aug:
M=jul;break;
case sep:
M=aug;break;
case oct:
M=sep;break;
case nov:
M=oct;break;
case dec:
M=nov;break;
}
return M;
}

void print_month (month M)
{
switch (M)
{
case jan:
printf("January");break;
case feb:
printf("February");break;
case mar:
printf("March");break;
case apr:
printf("April");break;
case may:
printf("May");break;
case jun:
printf("June");break;
case jul:
printf("July");break;
case aug:
printf("August");break;
case sep:
printf("September");break;
case oct:
printf("October");break;
case nov:
printf("November");break;
case dec:
printf("December");break;
}
}
void main()
{
month M;
printf("Table of months and their predecessors\n");
printf("\n %16s%16s\n", "Month", "Predecessor");
for(M = jan; M <= dec; M++) /*ERROR HERE*/
{
printf("");
print_month(M);
printf("");
print_month(previous_month(M));
putchar('\n');
}
}

[Hammer]

I get the same error when I compile this code as C++, but not when I compile as C.

[correlcj]

Hello Hammer,
According to my notes it should have worked. I am using Microsoft C++ software and every other program I have ran has worked. Strange huh?

[correlcj]

Well join the club because it aint working and i have started drinkning, folks!
PEACE OUT!

[Prelude]

>void main()
Um, no. main returns an int, even in C++.

In C your program works correctly because the enum identifiers are simply integers. In C++ there is a much stricter type checking so you either have to bend over backwards to increment an enum (which is an abuse of the language anyway, so such support was not included), or find some other way to do what you want. Perhaps a wrapper function or class. In case you were wondering about the bend-over-backwards way, it involves casting and may or may not be safe AFAIK:

for(M = jan; M <= dec; M = (enum month)( (int)M + 1 ))

-Prelude