new to D2.0 , invariant problem

[Steven Schveighoffer]

"MikeRJ" wrote
> For some reason i think DM 1.0 is slowly dieing as i see tons of new 
> features in D 2.0's phobos not implemented in D 1.0  so im trying to 
> migrate to D2.0
>
> my 1st problem is when i compile code:
>
> bool open(char[] fn, char[] mode="rb")
> {
> filename=fn.dup;
> file = fopen(toStringz(filename), toStringz(mode));
> if (!file) return false;
> return true;
> }
>
> i receive error:
>
>>> cannot implicitly convert expression ("rb") of type invariant(char[2u]) 
>>> to char[]|
> can anyone help here. thanks in advance.

The correct const-contract usage is:

bool open(const(char)[] fn, const(char)[] mode = "rb")

That is, you are saying open does not modify fn or mode.  It simply uses 
them as input parameters.

The D1/D2 compatible version that Kagamin posted is also legal (and pretty 
much the same thing).

-Steve