Talk:Typedef

Can anyone tell me what typedef uint32 A; would do ?

It would create a new type named 'A' that would essentially just be an alias for uint32. You could then create variables like this: 'A newvariables = 3;' Jaddle 17:06, 14 May 2007 (UTC)[reply]

= 3 --193.136.128.14 13:12, 17 May 2007 (UTC)[reply]

It would be nice to have an explanation of the syntax of recursive typedefs

For example, in C:

int main() {

typedef struct { int key; struct MyType* next; } MyType;

MyType a; MyType b;

MyType* aptr; MyType* bptr;

aptr = &a; bptr = &b;

aptr->key = 3; aptr->next = bptr;

}

The word "struct" is required before the phrase "mytype* next;" The GNU C compiler (3.4.6) warns that "aptr->next = bptr;" is an assignment of incompatible pointer types. —Preceding unsigned comment added by 155.148.36.138 (talk) 14:31, 6 September 2007 (UTC)[reply]

Note that the example given in the page is an excellent example of everything that can go wrong with typedefs. First, your typedef is usually in a separate file, so all the coder will see is:

apple coxes;

Now, ok, what can I do with coxes that are of type apple? Eat them? No I can increment them:

coxes += 1

So what exactly happens when you increment an apple? Especially in C++ with type overloading? All you've done is obscure the type of the variable. The data type should specify the variables _data_ _type_. Not describe it. That's what the name is for. The following code would be much, much clearer:

int coxe_apple_cnt = 0;

Now we have a variable that is a count of the number of coxe apples (coxe is a type of apple, I presume). It's type is int. Now we have a much clearer notion of what:

coxe_apple_cnt++;

Does.

So what's good about typedefs again?