<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;"> Please am a total beginner can you give me an example of how to use the map. thanks for your reply --- On Fri, 12/17/10, Raphael Collet <rco@missioncriticalit.com> wrote: <blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;"> From: Raphael Collet <rco@missioncriticalit.com> Subject: Re: [mercury-users] Converting List To List Of Tuples To: mercury-users@csse.unimelb.edu.au Cc: "win1for@yahoo.com" <win1for@yahoo.com> Date: Friday, December 17, 2010, 3:44 AM <div class="plainMail">Dear user, I suggest you to have a look at the modules map, pair and assoc_list. With a map, you will be able to build the frequency map. Start from an empty map, then increment the frequency of each character you find in the string. The predicate string.foldl/4 is useful to iterate over all the characters of the string. To convert the map into a list of pairs, you may simply use ListOfPairs = map.to_assoc_list(FrequencyMap) In your case, the result will be of type list(pair(char, int)). Note that the pair is not strictly a tuple, but a more specific type for a tuple of exactly two elements. The last point you need is to sort the list with list.sort/3. Simply define a comparison predicate to compare two values of type pair(char, int): order them by their second components. Something like: :- pred compare_freq(pair(K, int), pair(K, int), comparison_result). :- mode compare_freq(in, in, out) is det. compare_freq(X1 - F1, X2 - F2, Result) :- compare(Result, F1, F2). The predicate compare/3 and its associated types is defined in the module builtin. I hope this will help you. Cheers, Raphael On 12/17/2010 05:22 AM, <a ymailto="mailto:win1for@yahoo.com" href="/mc/compose?to=win1for@yahoo.com">win1for@yahoo.com</a> wrote: > Hello, > > > I am just a total beginner in mercury and finding it hard to solve this > problem. I want to convert a list to a list of tupples sorted from > smaller to higher frequenties. Eg: > > |string.to_char_list("this is a test") becomes > > [{'a', 1}, {'e', 1}, {'h', 1}, {'i', 2}, {' ', 3}, {'s', 3}, {'t', 3}] > > OR > > [3,2,1,2,1,1,2] becomes > > [{3, 1}, {1, 3}, {2, 3}] > | > > You can see that the list of tuples are sorted from smaller to higher > frequenties. > > I am asking if someone can help me to solve this or point me to a > tutorial where i can find more tips to do it. > > > Thanks for your reply. > > -------------------------------------------------------------------------- mercury-users mailing list Post messages to: <a ymailto="mailto:mercury-users@csse.unimelb.edu.au" href="/mc/compose?to=mercury-users@csse.unimelb.edu.au">mercury-users@csse.unimelb.edu.au</a> Administrative Queries: <a ymailto="mailto:owner-mercury-users@csse.unimelb.edu.au" href="/mc/compose?to=owner-mercury-users@csse.unimelb.edu.au">owner-mercury-users@csse.unimelb.edu.au</a> Subscriptions: <a ymailto="mailto:mercury-users-request@csse.unimelb.edu.au" href="/mc/compose?to=mercury-users-request@csse.unimelb.edu.au">mercury-users-request@csse.unimelb.edu.au</a> -------------------------------------------------------------------------- </div></blockquote></td></tr></table>