<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;">Hi, I have implemented the following code but its not compiling: :- module oplossing. :- interface. :- import_module io. :- pred main(io.state::di, io.state::uo) is det. :- implementation. :- import_module int, list,string,map. :- func tabel(list(T)) = list({T,int}). tabel([X|Xs]) = map.init(M), map.to_assoc_list(helper([X|Xs],M,1000)) . :- func helper(list(T),map(T),T) = map(T). helper([X|Xs],Map,VorigElement) = (if X = VorigElement then map.set(Map, X, map.search(Map,X)+1),helper(Xs, Map,X) else if X = [] then Map else map.set(Map, X, 1),helper(Xs, Map,X) ). This is the compile errors i get: oplossing.m:020: In definition of function `oplossing.helper'/5: oplossing.m:020: error: undefined type `map'/1. oplossing.m:020: In definition of function `oplossing.helper'/5: oplossing.m:020: error: undefined type `map'/1. oplossing.m:015: Error: clause for predicate `oplossing.,/2' oplossing.m:015: without preceding `pred' declaration. The problem has to do with the declaration of the "map". Can you please help me debugit? Thank you --- 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, 6:33 AM <div class="plainMail">Dear anonymous user, What you ask for looks a lot like a homework... I ain't going to do the homework for you. Here are a few hints, though. The function map.init returns an empty map. That's where you should start from. The predicate map.set/4 (and the function map.set/3) allows you to set the value associated to a key in the map. In your case, this could be the current frequency of a character. The predicate map.search/3 looks up for a given key, and return the corresponding value. You can use this to retrieve the frequency of a character. The typical use-case is: ( map.search(Map, Key, Value) -> % do something with the value ; % no value for key, do something else ) Cheers, Raphael On 12/17/2010 11:56 AM, <a href="compose?to=win1for@yahoo.com">win1for@yahoo.com</a> wrote: > > 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 /<<a href="compose?to=rco@missioncriticalit.com">rco@missioncriticalit.com</a>>/* wrote: > > > From: Raphael Collet <<a href="compose?to=rco@missioncriticalit.com">rco@missioncriticalit.com</a>> > Subject: Re: [mercury-users] Converting List To List Of Tuples > To: <a href="compose?to=mercury-users@csse.unimelb.edu.au">mercury-users@csse.unimelb.edu.au</a> > Cc: "<a href="compose?to=win1for@yahoo.com">win1for@yahoo.com</a>" <<a href="compose?to=win1for@yahoo.com">win1for@yahoo.com</a>> > Date: Friday, December 17, 2010, 3:44 AM > > 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 href="compose?to=win1for@yahoo.com">win1for@yahoo.com</a> > </mc/compose?to=<a href="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 href="compose?to=mercury-users@csse.unimelb.edu.au">mercury-users@csse.unimelb.edu.au</a> > </mc/compose?to=<a href="compose?to=mercury-users@csse.unimelb.edu.au">mercury-users@csse.unimelb.edu.au</a>> > Administrative Queries: <a href="compose?to=owner-mercury-users@csse.unimelb.edu.au">owner-mercury-users@csse.unimelb.edu.au</a> > </mc/compose?to=<a href="compose?to=owner-mercury-users@csse.unimelb.edu.au">owner-mercury-users@csse.unimelb.edu.au</a>> > Subscriptions: <a href="compose?to=mercury-users-request@csse.unimelb.edu.au">mercury-users-request@csse.unimelb.edu.au</a> > </mc/compose?to=<a href="compose?to=mercury-users-request@csse.unimelb.edu.au">mercury-users-request@csse.unimelb.edu.au</a>> > -------------------------------------------------------------------------- > > </div></blockquote></td></tr></table>