Subj : Re: any function to handle this kind of counting?
To   : comp.programming
From : cri
Date : Sat Jul 30 2005 09:50 pm

On Fri, 29 Jul 2005 23:30:10 +0800, "Ross" <a@cuhk.edu.hk> wrote:

>Dear all,
[snip]
>and then i want to count, say, for "1", there are two A's, one E, ...
>
>it seems that a for loop can do the job but as we don't know how many 
>instances there are, i.e. don't know A, C, E and then what will occur in 
>this corresponding vector, is there any function which is devoted to handle 
>this kind of counting problem? thx!! 

You didn't specify what language you mean to use (though I suspect
it's something from the C family) so you've opened the flood gates to
the usual suspects puffing off their favorite language du jour.
(Nothing like mixing a few metaphors.)  Just to join the fun, here the
code in San, a language I am developing.  (Not yet available, sorry.)

	paired[].a = a[]; paired[].b = b[]
	begin foreach pair in paired[]
		count[pair.a].list.{pair.b} = @+1
		end
	begin foreach val in count[]
		emit val ":"
		[val.list.[] | emit "(" %1'name ": " %1 ")" ]
		emit \n
		end

I presume that the code is suitably cryptic for those not familiar
with the syntax.

More to the point the general answer to your question is that few
languages, perhaps none, would have a specific function that meets
your particular need.  That said, there are several ways that one can
do this.  One is to build an array of lists (that's what the above
code does), another is to build a matrix with rows being integers, the
columns being letters, and the cells containing counts.  One can treat
the two vectors as paired elements and first sort on letter, then on
integer.  You can put the whole thing in a tree with nodes containing
counts.  USW.



Richard Harter, cri@tiac.net
http://home.tiac.net/~cri, http://www.varinoma.com
Save the Earth now!!
It's the only planet with chocolate.

.