Task to throw away string parts, use joiner and splitter not very successful

[Dfr]

Hello, i have string like "this.is.a.string" and want to throw 
away some parts separated by dots, here is first attempt:

name = "this.is.a.string"; // <-- want to make "this.is.a" from 
this
auto nameparts = splitter(name, '.');
auto name1 = joiner(nameparts[0 .. $-1], '.');

And got this error: "Error: Result cannot be sliced with []"

So, kinda fixed it (correct way?):

name = "this.is.a.string";
auto nameparts = splitter(name, '.').array;
auto name1 = joiner(nameparts[0 .. $-1], '.');

got this:

Error: template std.algorithm.joiner does not match any function 
template declaration. Candidates are:
/usr/include/dmd/phobos/std/algorithm.d(2846):        
std.algorithm.joiner(RoR, Separator)(RoR r, Separator sep) if 
(isInputRange!RoR && isInputRange!(ElementType!RoR) && 
isForwardRange!Separator && is(ElementType!Separator : 
ElementType!(ElementType!RoR)))

Stuck here, thank you for any help.