Convert hex to binary

[nrgyzer via Digitalmars-d-learn]

On Friday, 24 April 2015 at 18:45:55 UTC, Jesse Phillips wrote:
> On Friday, 24 April 2015 at 18:14:07 UTC, nrgyzer wrote:
>> Hi,
>>
>> I'm looking for a function that converts my hex-string to a 
>> binary representation. In Python I write the following:
>>
>> myHex = "123456789ABCDEF"
>> myBin = myHex.decode('hex')
>>
>> But how to do the same in D? Is there any function?
>>
>> Thanks for suggestions!
>
>     import std.stdio;
>     void main(){
>         import std.conv;
>         import std.format;
>
>         auto i = to!ulong("123456789ABCDEF", 16);
>
>         writeln(format("%b", i));
>     }

Thanks to all of you for the solutions, but what if the 
hex-string exceeds the limit of ulong, for instance 
"123456789ABCDEF0123456789ABCDEF1234". How to convert them to a 
ulong-array?