The following fails with : Error: "" is not an lvalue

void f( inout char [] x = "" ){ }

void main ()
{
  f();
}


Why is this not allowed ?

Charlie wrote:
> The following fails with : Error: "" is not an lvalue
> 
> void f( inout char [] x = "" ){ }
> 
> void main ()
> {
>   f();
> }
> 
> 
> Why is this not allowed ?

What would this do?

void f( inout char [] x = "" )
{
	x = "world";
}

It amounts to "take a literal reference to a static string and set it to something else". It doesn't really have a meaning.

You could try shelling it by hand.

void f() { char[] x = null; f(x);}

Yea I was trying to abuse it, you're right it shouldn't work with default parameters, what I was really trying to do was something like

char [] x = char[]

Charlie

BCS wrote:
> Charlie wrote:
>> The following fails with : Error: "" is not an lvalue
>>
>> void f( inout char [] x = "" ){ }
>>
>> void main ()
>> {
>>   f();
>> }
>>
>>
>> Why is this not allowed ?
> 
> What would this do?
> 
> void f( inout char [] x = "" )
> {
>     x = "world";
> }
> 
> It amounts to "take a literal reference to a static string and set it to something else". It doesn't really have a meaning.
> 
> You could try shelling it by hand.
> 
> void f() { char[] x = null; f(x);}

Charlie wrote:
> Yea I was trying to abuse it, you're right it shouldn't work with default parameters, what I was really trying to do was something like
> 
> char [] x = char[]
> 
> Charlie
> 

Are you looking for some sort of "stuff in a throw away value" feature?

void foo(int i, inout char[] foo = /** somthing **/ )
{
	foo = "hello";
}

char[] a;
foo(1, a);
assert(a == "hello");
foo(1); // no side effects

What would be nice would be something like "Non l-values used for inout parameters get passed as copies and discarded after use."

BCS wrote:
> Charlie wrote:
>> Yea I was trying to abuse it, you're right it shouldn't work with default parameters, what I was really trying to do was something like
>>
>> char [] x = char[]
>>
>> Charlie
>>
> 
> Are you looking for some sort of "stuff in a throw away value" feature?
> 
> void foo(int i, inout char[] foo = /** somthing **/ )
> {
>     foo = "hello";
> }
> 
> char[] a;
> foo(1, a);
> assert(a == "hello");
> foo(1); // no side effects
> 
> What would be nice would be something like "Non l-values used for inout parameters get passed as copies and discarded after use."
> 

Yes thats what I was looking for :).

Charlie