C + + I want to use this (b)

What do you need to pay attention to from pure C environment to C + + environment?

Yes, although C + + has been claimed to be compatible with C, and many people even think C is a C + + subset, but C-brain residue must know that the two have a great difference!

The following points are more prominent, and later I add the other:

1. About Type conversions

C is weak type, at least less than C + + weak, under C Many types of conversion we do not care, the compiler will default, up to some nasty compiler (such as a soft home) will give a warning, but in C + + is not the same, these are error!! You do not show the declaration, do not think cross-type!! In fact, this is a good thing, more dozen letters, but the code is clear and rigorous:)

Example

In C, you write this:
　　
int* p;
p = malloc (* sizeof (int));

In C + +, you have to write this:
　　
int* p;
p = (int *) malloc (Ten * sizeof (int));

2. About character arrays

In C, you can declare an array of characters, which is exactly the length of the string, that is: there is no place to ' s ', but in C + + You cannot do this:

char s[3] = "abc"; ( correct in C, error in C + +).

My advice is: if you are a normal human being, you will also write in C:

Char s[4] = "ABC";

but in fact the best way to do this is: char s[] = "abc"; isn't it??

3. About nested type definitions

Example

struct S {
int A;
struct T {
int t;
} b;
int C;
Enum e {V1, V2} e;
};

struct T x;
Enum E y;

The above code in C no problem, this is because S, T, e Three of the scope (scope) is the same, but in C + +, is really wrong! In C + +, the scope of T and E is in S, want to use outside only s::t, which involves the problem of namespaces, we will say later.

But even in C, I will put E and t alone to define, this kind of nested writing, always have rushes feeling ~ ~

4. About enum types

We all know that in C the enumeration is the same as the integral type, and the enumeration is the integer, so we do this:

Enum RGB {red, green, blue} RGB;
++rgb;

Oh, look, how wonderful the world is. However, the world of C + + is brutal, enumerations are independent types, and the integer operators such as + + are not supported. So you say it doesn't matter:"rgb=rgb+1;" Just fine. It's a pity. It's wrong again. Yes, because there is no display of the type conversion, so the correct wording:

Enum RGB {red, green, blue} RGB;

RGB = RGB (RGB + 1);

Although some long, but fortunately, if your obsessive-compulsive disorder has reached the divine level, then there are ways to give the RGB Plus + + operator overload bar, the specific content later said.

5. About annotations

and/**/'s double annotation scheme has long been adopted by C, so there is nothing special to note, but you have to write:

i = j//* Comment */k;

So even God can not help you = =!

This time to write so much, next time to continue to add ~ ~