typedef a matrix

[QQ]

Hello

I am reading a program like

typedef BYTE M[5]

What does it mean?

I know if I typedef int a;

I can use a as int

but how about typedef BYTE M[5]?

Thanks a lot!

 

[pete]

Hello

I am reading a program like

typedef BYTE M[5]

What does it mean?

I know if I typedef int a;

I can use a as int

a is type int

but how about typedef BYTE M[5]?

M is type array of 5 BYTEs

 

[baumann@pan]

you can use M as a type, which occupies five-byte length memory space.
while int occupies four-byte length memory space for 32bits platform.

 

[Barry Schwarz]

Hello

I am reading a program like

typedef BYTE M[5]

What does it mean?

I know if I typedef int a;

I can use a as int

but how about typedef BYTE M[5]?

Thanks a lot!

M is now a synonym for the type "array of 5 BYTE".

M x;
would be identical to
BYTE x[5];


<<Remove the del for email>>

 

[osmium]

you can use M as a type, which occupies five-byte length memory space.
while int occupies four-byte length memory space for 32bits platform.

A reasonable guess, but that would only be true if there is code elsewhere
in the program that defines BYTE as a char of some sort. Neither BYTE or
byte are primitive types in the C language.

 

[Keith Thompson]

I am reading a program like

typedef BYTE M[5]

What does it mean?

Very likely, it means that the author is being foolish.

Using a typedef for an array type hides the fact that it's an array.
Since arrays are used differently from other types (e.g., an array
name is converted to a pointer in most contexts), this is usually a
bad idea.

 

[baumann@pan]

A reasonable guess, but that would only be true if there is code elsewhere
in the program that defines BYTE as a char of some sort. Neither BYTE or
byte are primitive types in the C language.

you are right, i have ignored the fact that BYTE is not primitive type
of c/c++.

so what i said above is not exactly.

 

[Ari Lukumies]

typedef BYTE M[5]

What does it mean?

Using a typedef for an array type hides the fact that it's an array.
Since arrays are used differently from other types (e.g., an array
name is converted to a pointer in most contexts), this is usually a
bad idea.

However, it makes a program easier to write, in many cases such as the
type is expected as a parameter to a function, for example (not that
I'd recommend it, though).

-atl-