Re: if vs. when vs. and: style question

[Rusi]

On Tuesday, March 24, 2015 at 7:54:43 AM UTC+5:30, Emanuel Berg wrote:
> "Pascal J. Bourguignon"  writes:
> 
> > In general, WHEN is better than IF.
> >
> > Also, (unless (e1) (e2)) is better than (if (not (e1))
> > (e2)).
> >
> > Notably, WHEN and UNLESS have an implicit progn:
> 
> "In general", you say. Is there any other advantage
> save for not having to do the explicit `progn' and/or
> `not'?

In general weaker is better
http://www.w3.org/2001/tag/doc/leastPower.html

(when a b) ≡ (if a b)
However (if a b c) ≡ (when ??)

Other example:

destructuring-bind is strictly weaker than if/cond and so better when usable