Author Topic: Integer by reference..  (Read 9142 times)

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Offline rabbit

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Re: Integer by reference..
« Reply #15 on: February 08, 2007, 07:54:06 pm »
What?  That's the entire point of Java: an overabundance of objects.  You're not supposed to return a pointer, you're supposed to return an object.

Offline kalaka

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Re: Integer by reference..
« Reply #16 on: February 08, 2007, 07:58:22 pm »
It's what anyone who's gotten past chapter 2 of "Java for Dummies" should think.
Crap, I knew I should've read chapter 2...

Offline Sidoh

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Re: Integer by reference..
« Reply #17 on: February 08, 2007, 08:38:05 pm »
What?  That's the entire point of Java: an overabundance of objects.  You're not supposed to return a pointer, you're supposed to return an object.

I said "you bug me," not "I'm unable to decipher your hyperbole."

Offline iago

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Re: Integer by reference..
« Reply #18 on: February 08, 2007, 09:43:01 pm »
If you need to return more than a single variable, then you probably have a design issue. 

I think it might work best like this (in general):

int val1, val2;
VersionDatachecker vd = new VersionDatachecker();
vd.go(list, of, variables);
val1 = vd.getVal1();
val2 = vd.getVal2();

That's likely a cleaner design, and more "proper", in many respects.

Creating an object to return a parameter value is a gross kludge. It was a killable offense back when I was a marker.

Offline Joe

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Re: Integer by reference..
« Reply #19 on: February 09, 2007, 04:17:21 am »
Here you go:

Code: [Select]
package versioning;

public class CheckRevisionResults
{

private int m_verhash;
private int m_checksum;
private byte[] m_statstring;

public CheckRevisionResults(int verhash, int checksum, byte[] statstring)
{
m_checksum = checksum;
m_verhash = verhash;
m_statstring = statstring;
}

public int getChecksum()
{
return m_checksum;
}

public int getVerhash()
{
return m_verhash;
}

public byte[] getStatstring()
{
return m_statstring;
}
}

getVersionCheck returns that.

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I'd personally do as Joe suggests

You might be right about that, Joe.


Offline Chavo

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Re: Integer by reference..
« Reply #20 on: February 09, 2007, 10:09:22 am »
If you need to return more than a single variable, then you probably have a design issue. 

Returning an object that acts as a data structure encapsulating a number of related variables IS returning a single variable (or at least a reference to one).  That's not a design issue... Writing 2 methods just to return 2 seperate values that you are going to combine anyway or that causes unnecessary copying of code is a bigger design problem than returning an object instead of a primitive ><

Quote
nt val1, val2;
VersionDatachecker vd = new VersionDatachecker();
vd.go(list, of, variables);
val1 = vd.getVal1();
val2 = vd.getVal2();
This makes sense when Val1 and Val2 are not dependent variables or are not going to be used in the same place.

Quote
int val1, val2;
VersionDatachecker vd = new VersionDatachecker();
vd.go(list, of, variables);
val1 = vd.getVal1();
val2 = vd.getVal2();
computeNewVal(val1, val2);
If I'm just passing those 2 variables into a new method, that's fine, it is more flexible (not more 'correct').  It is not incorrect to write a method such that:

Quote
int val1, val2;
VersionDatachecker vd = new VersionDatachecker();
vd.go(list, of, variables);
vallist = vd.getVariableList();
vallist = computeNewVals(vallist);
//or even better
computeNewVals(vd);

If you are writing a utility class and looking to maximize reusability, it makes sense to break things down, but that's hardly a design issue to not use Objects where its easier or makes sense.



Offline nslay

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Re: Integer by reference..
« Reply #21 on: February 09, 2007, 03:54:36 pm »
If you need to return more than a single variable, then you probably have a design issue. 

I think it might work best like this (in general):

int val1, val2;
VersionDatachecker vd = new VersionDatachecker();
vd.go(list, of, variables);
val1 = vd.getVal1();
val2 = vd.getVal2();

That's likely a cleaner design, and more "proper", in many respects.

Creating an object to return a parameter value is a gross kludge. It was a killable offense back when I was a marker.

Just to expand on what unTactical said, as well as being a big C/C++/Fortran programmer (though I hate Fortran!), it is not only common to wish to return multiple pieces of data, but the ability to do so is built into all three of these languages.
While, C/C++ provide structs and classes, to "return" multiple pieces of data, Fortran actually defines a class of "subprogram" known as a "subroutine"
A subroutine is basically a C++ void function that accepts all references.
Here's a practical example where I want two pieces of data returned in fortran (95):
Code: [Select]
SUBROUTINE boxmuller(x,y)
  IMPLICIT NONE
  DOUBLE PRECISION, PARAMETER :: PI = 3.14159265359d0
  DOUBLE PRECISION, INTENT(OUT) :: x, y
  DOUBLE PRECISION :: u1, u2
  CALL RANDOM_NUMBER(u1)
  CALL RANDOM_NUMBER(u2)
  x = SQRT(-2.d0*LOG(u1))*COS(2.d0*PI*u2)
  y = SQRT(-2.d0*LOG(u1))*SIN(2.d0*PI*u2)
END SUBROUTINE boxmuller
This returns two independent variates distributed on N(0,1) generated from Box-Muller.

Here's a practical example in C
Code: [Select]
int tunman_getaddr( struct tunman *tn, struct sockaddr *addr, struct sockaddr *b
road ) {
        struct ifconf ifc;
        struct ifreq ifr;
        int s = socket( AF_INET, SOCK_DGRAM, IPPROTO_UDP );
        if ( s == -1 ) return -1;
        memset( &ifc, 0, sizeof(ifc) );
        strncpy( ifr.ifr_name, tn->ifnam, sizeof( ifr.ifr_name ) );
        ifc.ifc_len = sizeof(ifr);
        ifc.ifc_req = &ifr;
        if ( ioctl( s, SIOCGIFCONF, &ifc ) == -1 ) {
                close( s );
                return -1;
        }
        close( s );
        memcpy( addr, &ifc.ifc_req->ifr_addr, sizeof(*addr) );
        memcpy( broad, &ifc.ifc_req->ifr_broadaddr, sizeof(*broad) );
        return 0;
}

In this example, I not only return an indicator for error, but I also return two pieces of information, an interface's IP address and broadcast address.  The ioctl() SIOCGIFCONF also returns a buffer of ifreqs that hold the interface's IP address and aliases.  These types of operations are very common in Unix...doing something like:
getipaddr("eth0", &ip);
getbroad("eth0",&broad);
getmask("eth0", &mask);
getstate("eth0", &up );
etc...is extremely redundant!
« Last Edit: February 09, 2007, 04:04:54 pm by nslay »
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Offline MyndFyre

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Re: Integer by reference..
« Reply #22 on: February 09, 2007, 04:49:56 pm »
In this example, I not only return an indicator for error, but I also return two pieces of information, an interface's IP address and broadcast address.  The ioctl() SIOCGIFCONF also returns a buffer of ifreqs that hold the interface's IP address and aliases.  These types of operations are very common in Unix...doing something like:
getipaddr("eth0", &ip);
getbroad("eth0",&broad);
getmask("eth0", &mask);
getstate("eth0", &up );
etc...is extremely redundant!

Ahh, very true.  *HOWEVER*, the C language was developed before structured exception handling was really a standard (or at the very least, it wasn't considered a major feature of C).  It isn't appropriate in languages with SEH (except C++ apparently, probably because of its C roots) to return error codes.
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Offline Joe

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Re: Integer by reference..
« Reply #23 on: February 09, 2007, 06:06:51 pm »
Mine was somewhat the same idea. The way RCRS worked is each field was a different packet, but now that I'm using BNLS, it seemed impracticle to send the same packet three times over in the seperate functions.
I'd personally do as Joe suggests

You might be right about that, Joe.