Re: function ref param vs pointer param

[bearophile via Digitalmars-d-learn]

On Friday, 24 April 2015 at 13:39:35 UTC, ref2401 wrote:

processPointer(ms);
I think doing this way is more descriptive.
Now all readers know that ms might be changed inside the 
function.


C# avoids that problem requiring (in most cases) the usage of 
ref at the calling point too. But this idea was refused for D 
(also because it goes against UFCS chains).


Bye,
bearophile

function ref param vs pointer param

[ref2401 via Digitalmars-d-learn]

What advantages do ref params give over pointer params?

struct MyStruct {
string str;

this(string str) { this.str = str; }
}

void processRef(ref MyStruct ms) {
writeln(processRef: , ms);
}

void processPointer(MyStruct* ms) {
writeln(processPointer: , *ms);
}

void main(string[] args) {
	auto ms = MyStruct(the ultimate answer to everythin is the 
number 42);


processRef(ms);
processPointer(ms);
}

Re: function ref param vs pointer param

[Ali Çehreli via Digitalmars-d-learn]

On 04/24/2015 06:23 AM, ref2401 wrote:

 What advantages do ref params give over pointer params?

Another difference is that a ref parameter is not null and what is 
referred to is not an rvalue.


However, it is possible to break that expectation if a pointer is 
dereferenced and passed to a ref-taking function but then the actual 
object is gone before the reference is used.


Ali

Re: function ref param vs pointer param

[ref2401 via Digitalmars-d-learn]

Thank you

Re: function ref param vs pointer param

[bearophile via Digitalmars-d-learn]

ref2401:


void processRef(ref MyStruct ms) {
writeln(processRef: , ms);
}

void processPointer(MyStruct* ms) {
writeln(processPointer: , *ms);


ref params don't need the * every time you use them inside the 
function, and don't need the  when you call the function.


Bye,
bearophile

Re: function ref param vs pointer param

[Steven Schveighoffer via Digitalmars-d-learn]

On 4/24/15 9:23 AM, ref2401 wrote:

What advantages do ref params give over pointer params?

struct MyStruct {
 string str;

 this(string str) { this.str = str; }
}

void processRef(ref MyStruct ms) {
 writeln(processRef: , ms);
}

void processPointer(MyStruct* ms) {
 writeln(processPointer: , *ms);
}

void main(string[] args) {
 auto ms = MyStruct(the ultimate answer to everythin is the number
42);

 processRef(ms);
 processPointer(ms);
}


A ref param is somewhat safer, because you cannot do pointer arithmetic 
on it. A ref will ALWAYS point at the same memory location, because it 
cannot be rebound.


The compiler can also take advantage of the characteristics of ref, as 
it does with the -dip25 switch.


-Steve

Re: function ref param vs pointer param

[ref2401 via Digitalmars-d-learn]

processPointer(ms);
I think doing this way is more descriptive.
Now all readers know that ms might be changed inside the function.