read_in([W|Ws]) :- get0(C), readword(C,W,C1), restsent(W,C1,Ws).

restsent( W,_,[]) :- lastword(W), !.
restsent(W,C,[W1|Ws]) :- readword(C,W1,C1), restsent(W1,C1,Ws).

readword(C,W,C1) :- single_character(C), !, name(W,[C]), get0(C1).
readword(C,W,C2) :-
	in_word(C,NewC), !,
	get0(C1),
	restword(C1,Cs,C2),
	name(W,[NewC|Cs]).
readword(C,W,C2) :- get0(C1), readword(C1,W,C2).

restword(C,[NewC|Cs],C2) :-
	in_word(C,NewC), !,
	get0(C1),
	restword(C1,Cs,C2).
restword(C,[],C).

single_character(44).  /* , */
single_character(59).  /* ; */
single_character(58).  /* : */
single_character(63).  /* ? */
single_character(33).  /* ! */
single_character(46).  /* . */

in_word(C,C) :- C>96, C<123.                /* a b..z */
in_word(C,L) :- C>64, C<91, L is C+32.      /* A,B..Z */
in_word(C,C) :- C>47, C<58.                 /* 1,2,..9 */
in_word(39,39).                             /*  ' */
in_word(45,45).                             /* - */

lastword( '.' ).
lastword( '!' ).
lastword( '?' ).