[Article Submission] Have Your Efficiency, and Flexibility Too

[Nick Sabalausky]

"Timon Gehr" <timon.gehr at gmx.ch> wrote in message 
news:is2lts$2fcn$1 at digitalmars.com...
> bearophile wrote:
>> ...
>> A shorter way to write it:
>>
>> void addGizmos(int numPorts, bool isSpinnable, int numGizmos) {
>>     foreach (np; TypeTuple!(1, 2, 3, 5, 10))
>>         if (numPorts == np) {
>>             foreach (b; TypeTuple!(true, false))
>>                 if (isSpinnable == b)
>>                     addGizmosTo!(np, b)(numGizmos);
>>             return;
>>         }
>>
>>     throw new Exception(text(numPorts) ~ "-port Gizmo not supported.");
>> }
>>
>> Bye,
>> bearophile
>
> Nice, but isSpinnable is always checked twice with your approach. Better:
>
> void addGizmos(int numPorts, bool isSpinnable, int numGizmos) {
>    foreach (np; TypeTuple!(1, 2, 3, 5, 10))
>        if (numPorts == np) {
>                if (isSpinnable) addGizmosTo!(np, true)(numGizmos);
>                else addGizmosTo!(np, false)(numGizmos);
>            return;
>        }
>
>    throw new Exception(text(numPorts) ~ "-port Gizmo not supported.");
> }
>

I love this idea. I had no idea you could use TypeTuple for values. But it 
doesn't seem to be working in ths particular case. On the line that tries to 
call 'addGizmosTo' I get this compiler error:

Error: template instance cannot use local 'np' as parameter to non-global 
template addGizmosTo(int numPorts,bool isSpinnable)