Prolog has been used for many purposes, but its inventor, Alain Colmerauer, was interested in computational linguistics, and this remains a classic application for the language. Moreover, Prolog offers a number of tools which make life easier for computational linguists, and we are now going to start learning about one of the most useful of these: definite clause grammars, or DCGs as they are usually called.

The windows gleamed with light through the boughs—a small open space gave to view the left wing of the building—he could distinctly see the long range of illuminated apartments, figures moving to and fro, and the richly coloured fall of the draperies.

I have a vast inclination to get a pap-boat myself, and make him a present of it.

Observant visitors to any prison will quickly recognize commonalties in its inmate population. Not only do shared traits exist among the inmate population of any particular institution (intra-prison commonalties) but commonalties also exist among inmates nationwide (inter-prison commonalties).