how to remove duplicate code in functional style

[Alex]

On Friday, 23 November 2018 at 14:33:40 UTC, berni wrote:
> I've got the following code, which works, but obviously 
> contains duplication. Is there a way to move that 
> "dissection_available?...:..." to the place, where it should be?
>
>> return dissection_available
>>     ?solution.dup
>>              .transposed.map!(a=>a.map!(b=>"?#."[b]).array)
>>              
>> .zip(dissection.dup.transposed.map!(a=>a.map!(b=>"X#.?"[b]).array))
>>              .map!(a=>a[0].to!string~"  "~a[1].to!string)
>>              .join("\n")
>>              .to!string
>>     :solution.dup
>>              .transposed.map!(a=>a.map!(b=>"?#."[b]).array)
>>              .join("\n")
>>              .to!string;
>
> solution and dissection are of type const(int[][]).

Isn't the standard way of removing duplicate code in functional 
style to write more small grained functions?

like

return solution
                 . initialCommonOperation
                 . someAction(dissection, dissection_available)
                 . finalCommonOperation;

auto commonInitialCommonOperation(T)(T input)
{
     return 
solution.dup.transposed.map!(a=>a.map!(b=>"?#."[b]).array);
}

auto someAction(T, A)(T tmp, A dissection, bool 
dissection_available)
{
     return dissection_available ? 
tmp.zip(dissection.dup.transposed.map!(a=>a.map!
         (b=>"X#.?"[b]).array))
         .map!(a=>a[0].to!string~"  "~a[1].to!string) : tmp;
}

auto finalCommonOperation(T)(T tmp)
{
     return tmp.join("\n").to!string;
}

Don't know, if this compiles... but you get my point ;)