Programming Forums > Application Development > C

Navid · Jun 12th, 2005, 11:51 AM

Is is possible to have a function to return two values instead of one?
Or do i have to have two functions for each value?

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printf(" The two values returned: %d and %d", funct() );

L7Sqr · Jun 12th, 2005, 12:35 PM

You will want to use a structure to do what you are asking.

example:

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typedef struct {
   int x;
   int y;
} two_int_t;

From there you can either pass in a pointer to a function and fill in the values or use a structure (or pointer to) as a return value for the function.

And, btw, when you are calling a printf function (or any of the varidic funtions) You want to provide enough arguments for each of the format specifiers. i.e. for two %d's you will want two arguments passed to the function.
I assume you did that just for an example of your question, but thought I would comment anyway...

kirkl_uk · Jun 12th, 2005, 12:45 PM

Just for two integers, another option would be to provide references to the two:

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bool funct(int& x, int& y) {
  ...
}

Then you call the function like so:

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int x, y;

if(funct(x, y)) {
  printf("The two values returned: %d and %d", x, y);
}

This allows for you to return whether the function succeeded as well. Both methods put forward in this thread will work.

L7Sqr · Jun 12th, 2005, 12:55 PM

Agreed, references and bool return values would suffice in C++, but for a C program, they will not be of much assistance...

Dameon · Jun 12th, 2005, 1:58 PM

C and C++ both have the concept of references and pointers last I checked

kirkl_uk · Jun 12th, 2005, 2:04 PM

Maybe he is referring to the bool type.

uman · Jun 12th, 2005, 2:19 PM

C has references?

Ancient Dragon · Jun 12th, 2005, 2:21 PM

Quote:

Originally Posted by uman

C has references?

yes

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// c++ reference
void foo(int& x)
{
   x = 0;
}

// C reference
void foo(int* x)
{
   *x = 0;
}

stevengs · Jun 12th, 2005, 2:28 PM

Quote:

Originally Posted by Ancient Dragon

yes

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well, I reckon I am more confused than I had originally believed myself to be. I was certain that there were differences between references and pointers. My main argument would probably be: "Then why be there??" Isn't the use of references more restrictive (i.e. for safety) ?

I was also under the impression that standard C does not specify the use of references.. just goes to show what I know...

DaWei · Jun 12th, 2005, 2:35 PM

There is definitely a difference between a "reference" per C++ definition and a pointer. The choice of the term, "reference" for C++, was a little shaky, as pointers, labels, nicknames, aliases, are ALL references. However, one cannot pass a "reference" (as defined in C++) in C. The "&" operator is strictly an address-of operator and the use inside the function has to be the same as when dereferencing a pointer. In C++, on the other hand, a "reference" is an alias and a passed reference amounts to one fewer levels of indirection.

Jun 12th, 2005, 11:51 AM	#1
Navid Hobbyist Programmer Join Date: Feb 2005 Location: Canada Posts: 187 Rep Power: 4	Returning two values (solved) Is is possible to have a function to return two values instead of one? Or do i have to have two functions for each value? (Toggle Plain Text) printf(" The two values returned: %d and %d", funct() ); printf(" The two values returned: %d and %d", funct() ); Last edited by navnav; Jun 12th, 2005 at 4:47 PM.

Jun 12th, 2005, 12:35 PM	#2
L7Sqr Hobbyist Programmer Join Date: Jun 2005 Location: here Posts: 114 Rep Power: 0	You will want to use a structure to do what you are asking. example: (Toggle Plain Text) typedef struct { int x; int y; } two_int_t; typedef struct { int x; int y; } two_int_t; From there you can either pass in a pointer to a function and fill in the values or use a structure (or pointer to) as a return value for the function. And, btw, when you are calling a printf function (or any of the varidic funtions) You want to provide enough arguments for each of the format specifiers. i.e. for two %d's you will want two arguments passed to the function. I assume you did that just for an example of your question, but thought I would comment anyway...

Jun 12th, 2005, 12:45 PM	#3
kirkl_uk Programmer Join Date: Apr 2005 Location: England Posts: 86 Rep Power: 4	Just for two integers, another option would be to provide references to the two: (Toggle Plain Text) bool funct(int& x, int& y) { ... } bool funct(int& x, int& y) { ... } Then you call the function like so: (Toggle Plain Text) int x, y; if(funct(x, y)) { printf("The two values returned: %d and %d", x, y); } int x, y; if(funct(x, y)) { printf("The two values returned: %d and %d", x, y); } This allows for you to return whether the function succeeded as well. Both methods put forward in this thread will work. __________________ kirkl_uk

Jun 12th, 2005, 2:04 PM	#6
kirkl_uk Programmer Join Date: Apr 2005 Location: England Posts: 86 Rep Power: 4	Maybe he is referring to the bool type. __________________ kirkl_uk

Jun 12th, 2005, 2:35 PM	#10
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	There is definitely a difference between a "reference" per C++ definition and a pointer. The choice of the term, "reference" for C++, was a little shaky, as pointers, labels, nicknames, aliases, are ALL references. However, one cannot pass a "reference" (as defined in C++) in C. The "&" operator is strictly an address-of operator and the use inside the function has to be the same as when dereferencing a pointer. In C++, on the other hand, a "reference" is an alias and a passed reference amounts to one fewer levels of indirection. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Jun 12th, 2005, 12:55 PM	#4
L7Sqr Hobbyist Programmer Join Date: Jun 2005 Location: here Posts: 114 Rep Power: 0	Agreed, references and bool return values would suffice in C++, but for a C program, they will not be of much assistance...

Jun 12th, 2005, 1:58 PM	#5
Dameon Troll Join Date: Apr 2005 Location: Texas Posts: 732 Rep Power: 4	C and C++ both have the concept of references and pointers last I checked

Jun 12th, 2005, 2:19 PM	#7
uman Expert Programmer Join Date: Dec 2004 Posts: 794 Rep Power: 4	C has references?

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Programming Forums > Application Development > C

Returning two values