Re: Proposed algorithm library: reduce, combine, filter, guard

From: Alexander Belopolsky (belopols_at_[hidden])
Date: 2001-08-09 14:42:46

Your reduce seems to do the same as standard algorithm
accumulate.  See [lib.accumulate] 26.4.1
--- In boost_at_y..., farrow_at_t... wrote:
> 
> Using STL algorithms...
> I am unable to deduce a way of combining or reducing sequence
> containers into a single result or filtering arbitrary iterators
with
> a predicate.  So I have created these...
> 
> REDUCE: applies a binary operator where the first argument is the
> current intermediate result and the second is each value in the
> sequence.  The result of each function application becomes the new
> result.
> 
> Example:
> 
> vector<int> nums; //contains { 1, 2, 3 }
> int result = reduce(nums.begin(), nums.end(), plus<int>(), 0);
> //result = 6
> 
> COMBINE: applies the plus operator to the elements in a sequence
with
> a separator.  Mostly useful for containers of strings -- but not
> limited to that.
> 
> Example:
> 
> string sep("|");
> vector<string> strs; //contains { "a", "b", "c" }
> string result = combine(strs.begin(), strs.end(), sep)
> //result = "a|b|c"
> 
> FILTER: a wrapper for an iterator that applies a predicate functor.
> The resulting iterator only stops at objects that pass the
predicate.
> 
> vector<int> nums; //contains { 1, 15, 2, 10, 3 }
> int result = reduce(filter(nums.begin(),
>                            bind2nd(less_than<int>(),10)),
>                     nums.end(), plus<int>(), 0);
> //result = 6
> 
> GUARD: is the complement of FILTER.
> The resulting iterator only stops at objects that FAIL the
predicate.
> 
> 
> I have not found these (or the like) in STL or after looking thru
> several on-line repositories -- Boost and others recommended by
> "Effective STL" (by Meyers).
> 
> I don't contend that these interfaces are perfect and 
> I am happy to be refered to someone else's work.
> 
> Thanks,
> 
> Rob Farrow
> farrow_at_t...