Thread: ? about typedef

Hi ,

I am confused about what typedef means ?

for example:

"typedef double something; "

what exactly does this mean??

Thanks for any explanation!!

To define your own type based on other existing data types.
the syntax:

Code:

typedef   existing_type   new_type_name ;

where existing_type is a C++ fundamental or any other defined type and new_type_name is the name that the new type we are going to define will receive. For example:

typedef char C;
typedef short unsigned int USHORT;

then just use the new type word to declare variables

C 'a';
USHORT 5;

Typedef enforces strong typing, in accordance with general C++, therefore use this over Macro's..

--Placid

If it helps, I think you explained it better

--Placid

For an example of how to abuse typedef consult the windows.h header file.

it's also useful to substitute a shorter name for a type (which is always useful in avoiding typos).

ie:
typedef typename std::vector<Wrapper_of_type<T> >::iterator iter;

for (iter i=begin(); i != end(); ++i) ...

any change in the long name could be made at one place instead of many.

Yeah, doing something like:

std::vector<std::vector<float> > f(rowcount, std::vector<float>(colcount));

is not as nice as:

typedef std::vector<float> row;
typedef std::vector<row> fArray;

fArray f(rowcount, row(colcount));