<html> <head> <style> .hmmessage P { margin:0px; padding:0px } body.hmmessage { FONT-SIZE: 10pt; FONT-FAMILY:Tahoma } </style> </head> <body class='hmmessage'> Can anyone help me to explain the compilation errors? I am trying to combine elements two lists of type1 to get a list of type2. Thanks in advance... - %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% stormie@stormie-laptop:~/logic/dvl_mercury/testmod$ mmc --make exp1 Making Mercury/int3s/exp1.int3 Making Mercury/ints/exp1.int Making Mercury/cs/exp1.c exp1.m:040: In `combine'(in, in, out): exp1.m:040: error: determinism declaration not satisfied. exp1.m:040: Declared `det', inferred `semidet'. exp1.m:041: In argument 2 of clause head: exp1.m:041: unification of `HeadVar__2' and `list.[]' can fail. exp1.m:042: In argument 2 of clause head: exp1.m:042: unification of `HeadVar__2' and `list.[B | Bs]' can fail. %%%%%%%%%% Start of Mercury Code :- module exp1. :- interface. :- import_module io. :- pred main(io::di, io::uo) is det. :- implementation. :- import_module list,string. :- type type1 ---> t(string). :- type type2 ---> c(type1,type1). main(!IO) :- io.write_string('Halo!! !! \n', !IO), X = [t('1'),t('2'),t('3'),t('4')], Y = [t('a'),t('b'),t('c'),t('d')], combine(X,Y,Out), displayt2(Out,!IO). :- pred displayt1(list(type1)::in,io::di, io::uo) is det. displayt1([],!IO). displayt1([X|Xs],!IO):- displayt1(Xs,!IO), io.write(X,!IO). :- pred displayt2(list(type2)::in,io::di, io::uo) is det. displayt2([],!IO). displayt2([X|Xs],!IO):- displayt2(Xs,!IO), io.write(X,!IO). :- pred combine( list(type1)::in, list(type1)::in, list(type2)::out) is det. combine( [], [] ,G) :- G = []. combine( [A|As],[B|Bs], G):- combine(As, Bs, G1), append([c(A,B)],G1,G). %%%%%%%%%%%%%%%%%%%%%%% End of Mercury Code -- I am able to work out similar logic in prolog, e.g. with following using constraints combine( [], [] ,G) :- G = []. combine( [A|As],[B|Bs], G):- combine(As,Bs, G1), append([c(A,B)],G1,G) applying goal of ?- combine([x,y,z],[1,2,3],G). G = [c(x, 1), c(y, 2), c(z, 3)] ; No <hr />Find what you want @ www.eBay.com.au. <a href='http://a.ninemsn.com.au/b.aspx?URL=http%3A%2F%2Frover%2Eebay%2Ecom%2Frover%2F1%2F705%2D10129%2D5668%2D323%2F4%2F%3Fid%3D6&_t=763807330&_r=email_taglines_EBAY&_m=EXT' target='_new'>Make shopping exciting. </a></body> </html>