Idea: swap with multiple arguments

[Seb via Digitalmars-d]

On Thursday, 26 May 2016 at 02:17:20 UTC, Observer wrote:
> On Wednesday, 25 May 2016 at 17:08:02 UTC, Martin Tschierschke 
> wrote:
>> A newbee question about language design:
>> When I looked first time at Ruby I liked the simple a,b = b,a 
>> syntax,
>> so swap. Would it be theoretically possible to allow this?
>>
>> And if not, where does it breaks the general language design?
>
> There's something about this notation that immediately makes
> me think more generally.  swap is just the degenerate form
> of a more-general circular-shift operation in two different
> dimensions.  This form assumes that the shifting stops after 
> only
> a single shift position (or more generally, that the number of
> shift positions is odd); and having just two operands makes it
> unnecessary to specify whether the shifting is to the left or to
> the right.  But even a circular-shift operation is itself just a
> degenerate form of a more-general arbitrary-permutation 
> operation.
> Other permutations have common applicability in computer 
> science,
> such as the bit-reversed addressing used on DSP chips to support
> butterfly operations in FFT (actually, DFT) algorithms.  All of
> which makes me wonder:  if we want to generalize swap, should 
> we go
> farther than just one algorithmic stage?  How about a very 
> general
> routine that accepts a permutation mapping and a set of 
> arguments,
> and scrambles the arguments according to the mapping?

There's indexed, but it doesn't swap - it only provides access 
based on your permutation and only works if all data has a 
CommonType.

http://dlang.org/phobos/std_range.html#.indexed

For what it's worth, it's pretty cool to build rangified swaps of 
ranges - e.g. in combinatorics:

http://docs.mir.dlang.io/latest/mir_combinatorics.html