`examplevalues` property

[Andrea Fontana via Digitalmars-d]

On Monday, 3 August 2015 at 13:54:51 UTC, HaraldZealot wrote:
> On Monday, 3 August 2015 at 13:13:55 UTC, Andrea Fontana wrote:
>>
>> Why don't you use templates? Something like:
>>
>> enum ValueType
>> {
>> 	Init,
>> 	Min,
>> 	Max
>> }
>>
>> auto exampleValues(T)()
>> {
>> 	T[ValueType] retVal;
>>
>> 	retVal[ValueType.Init] = T.init;
>> 	static if (__traits(compiles, T.min)) retVal[ValueType.Min] = 
>> T.min;
>> 	static if (__traits(compiles, T.max)) retVal[ValueType.Max] = 
>> T.max;
>>
>> 	return retVal;
>> }
>>
>> exampleValues!int.writeln;
>> exampleValues!string.writeln;
>
> Good solution!
>
> But there is something that not perfect: it can be customizable 
> only with template specialization as I see. I want not only 
> standard values like `init` `max` or `min` but also some 
> example value like 1, 2, 3, 4, 5 for `int`. In last case your 
> template solution not so convenient as desired (introduction in 
> language feature like `.testValue1` seems ridiculous, and 
> without that only template specialization can provide 
> customization, as I have said).
>
> But this seems interesting direction, and easy to implement in 
> object.d (without library implementation, this feature have 
> little benefit).

You have to write the same amount of code.
It's just one line for each type... Something like:

import std.traits;

enum ValueType
{
	Init,
	Min,
	Max
}

auto exampleValues(T)()
{

	T[ValueType] retVal;
		
	retVal[ValueType.Init] = T.init;
	static if (__traits(compiles, T.min)) retVal[ValueType.Min] = 
T.min;
	static if (__traits(compiles, T.max)) retVal[ValueType.Max] = 
T.max;

	static if(isIntegral!T) 		return tuple!("defaults", 
"customs")(retVal, [1,2,3,4,5]);
	else static if(isFloatingPoint!T) 	return tuple!("defaults", 
"customs")(retVal, [1.0,2.0,T.nan]);
	else static if(isSomeString!T) 		return tuple!("defaults", 
"customs")(retVal, ["hello", "world"]);
	else return tuple!("defaults", "customs")(retVal, T[].init);
}