Program translate german numbers to english, and english to german
Source: Learn prolog now!, 2001, (course available on-line)
Program source code: german2english.pl
tran(eins,one). tran(zwei,two). tran(drei,three). tran(vier,four). tran(fuenf,five). tran(sechs,six). tran(sieben,seven). tran(acht,eight). tran(neun,nine). listtran([],[]). listtran([X|T1],[Y|T2]):-tran(X,Y), listtran(T1,T2).