boolean over multiple variables

[Rainer Deyke]

bearophile wrote:
> Nick Sabalausky:
>> Aside from that being how Python does it, why do you see that as
>> preferable?
> 
> Because: 1) linear searches in an array are damn common. I don't
> remember the results of my benchmarks, but until your integer arrays
> is quite longer than 30-50 items, performing a linear search is
> faster than a lookup in an AA, on DMD. On Tango this number is
> probably 70% higher 1b) In Python if you perform a "foo" in "barfoo"
> the language doesn't perform a linear search, it uses a much smarter
> search that has a complexity lower than the product of the two
> lengths, using a custom algorithm. So in D you can use the same
> syntax to search for substrings/subarrays. Where such smarter search
> is not possible, D can use a naive search. 2) It's really handy. I
> use isIn(item, items) to search on arrays in D, but having a item in
> items is nicer. 3) You can use the same syntax to search into
> anything that's lazily iterable too (a Range). This is very handy.

I would add to that:
4) Because 'in' is an operator, and operators are expected to bear a
greater weight than ordinary functions.

If 'in' was an ordinary method, say 'a.contains(b)', then I would choose
different method names for searching an array for a value and searching
an associative array for a key.  Probably something like:
  array.contains(value)
  associative_array.containsKey(key)

However, since 'in' already is an infix operator, it should have the
most widely applicable semantics.  Operators are heavyweight syntactic
sugar for function calls.  There is no room in D for operators that are
only rarely useful.


-- 
Rainer Deyke - rainerd at eldwood.com