Re: How make Optional pre determined parameter type without overload function?

[Marcone via Digitalmars-d-learn]

Now my slice works fine.

// Tipo Nulo.
class None {}

// Função slice()
auto slice(T1, T2, T3 = None)(T1 conteudo, T2 inicio, T3 fim = 
T3.init) {
        int start, end, startlen;
	static if (is(T2 == int)) {inicio = inicio < 0 ? conteudo.length 
+ inicio : inicio;}
	static if (is(T3 == int)) {fim = fim <= 0 ? conteudo.length + 
fim : fim;}
	static if (is(T2 == int)) {start = inicio;} else static if 
(is(T2 == string)){start = conteudo.countUntil(inicio);}
	static if (is(T2 == string)) {static if (is(T1 == 
string)){startlen = start + inicio.length + 1;} else {startlen = 
start + 1;}}
	static if (is(T3 == int)) {end = fim;} else static if (is(T3 == 
string)){end = startlen + conteudo[startlen..$].countUntil(fim);}
	static if (is(T3 == None)) {return conteudo[start];} else 
{return conteudo[start..end];}
}