Question

I’m reading about Typedef on wikipedia. Example mentioned on that page is

typedef int km_per_hour ;
typedef int points ;

km_per_hour current_speed ;
points high_score ;
...

void congratulate(points your_score) {
if (your_score > high_score)
...

Going further it says this which I’m not able to understand why?

void foo() {
unsigned int a;         // Okay
unsigned km_per_hour b; // Compiler complains
long int c;             // Okay
long km_per_hour d;     // Compiler complains
...

Why does the compiler complain for unsigned and long?

Answer 1

You cannot prepend signed or unsigned before a typedef‘d type. signed and unsigned can only modify basic integer types and do that directly.

The compiler parses signed or unsigned either alone or near char, short, int and long. In all other cases they are considered invalid/unexpected/misplaced.

In that sense, signed and unsigned don’t work as const or volatile modifiers.