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D - foreach gotchas

reply J Anderson <REMOVEanderson badmama.com.au> writes:
With the for each val is always a copy, which means code like below is 
incorrect.

int [] array;

foreach (int i, int val; array)
{
    val = 10;
}

I think in foreach val should be a reference. 

What's worse, is if you iterate through an array of structs with 
foreach.  In these cases there probably is a  performance hit due to the 
copy.

-Anderson
Dec 18 2003
parent reply Patrick Down <pat codemoon.com> writes:
You can do it with inout

J Anderson <REMOVEanderson badmama.com.au> wrote in
news:brsd95$9iu$1 digitaldaemon.com: 

 With the for each val is always a copy, which means code like below is
 incorrect.
 
 int [] array;
 
 foreach (int i, int val; array)
 {
     val = 10;
 }

foreach (inout int i, int val; array) { val = 10; }
 
 I think in foreach val should be a reference. 
 
 What's worse, is if you iterate through an array of structs with 
 foreach.  In these cases there probably is a  performance hit due to
 the copy.
 
 -Anderson
 
 

Dec 18 2003
parent J Anderson <REMOVEanderson badmama.com.au> writes:
Patrick Down wrote:

You can do it with inout
  

Thanks.
J Anderson <REMOVEanderson badmama.com.au> wrote in
news:brsd95$9iu$1 digitaldaemon.com: 

  

With the for each val is always a copy, which means code like below is
incorrect.

int [] array;

foreach (int i, int val; array)
{
    val = 10;
}
    

foreach (inout int i, int val; array) { val = 10; }
I think in foreach val should be a reference. 

What's worse, is if you iterate through an array of structs with 
foreach.  In these cases there probably is a  performance hit due to
the copy.

-Anderson


    


Dec 18 2003