xxxInPlace or xxxCopy?

[Jonathan M Davis]

On Wednesday 19 January 2011 18:23:14 Jerry Quinn wrote:
> Andrei Alexandrescu Wrote:
> > On 1/19/11 6:53 PM, Jonathan M Davis wrote:
> > > On Wednesday, January 19, 2011 15:33:16 Andrei Alexandrescu wrote:
> > >> I'm consolidating some routines from std.string into std.array. They
> > >> are specialized for operating on arrays, and include the likes of
> > >> insert, remove, replace.
> > >> 
> > >> One question is whether operations should be performed in place or on
> > >> a
> > 
> > >> copy. For example:
> > So I guess vote stays unchanged :o).
> > 
> > >> Thoughts?
> > > 
> > > Haven't we been using the approach that string operations generally
> > > make copies (in many cases slices) and marking functions that do it in
> > > place with InPlace?
> > 
> > Problem is, even though the example uses strings, the functions apply to
> > all arrays.
> 
> The big difference is operating on immutable arrays vs mutable ones.  For
> immutable arrays, you  have to do copies.  But mutable ones allow in-place
> editing.  If I'm working with mutable arrays of ints, I don't want to have
> to type InPlace after every function and I *really* don't want the array
> to be copied or efficiency will go down the tubes.
> 
> Nor do I want to add Copy to every string operation.  This might be an
> argument to leave the string functions where they are.  To a certain
> extent, strings are special, even though they really aren't.
> 
> Is it too ugly to contemplate algorithms doing in-place operations on
> mutable arrays and return a copy instead for immutable ones?

I'd say that yes, it's too ugly to contemplate. The reason is simple: the 
behavior of the function then changes drastically depending on whether the array 
you give it is immutable or not.

- Jonathan M Davis