CS 330 Lecture 39 – Logic programming
May 9, 2012 by Chris Johnson. Filed under
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cs330, lectures, spring 2012.
Agenda
- atoms and variables
- facts and rules
- a path in a graph?
- Prolog’s DFS algorithm
- even or odd?
- member?
- sorted?
- notmember?
- hascycle?
Code
pdb.pl
lang(scheme).
lang(c).
static(c).
staticlang(X) :- lang(X), static(X).
/* Graph stuff */
edge(a, b).
edge(b, e).
edge(b, d).
edge(c, d).
path(X, Y) :- edge(X, Y).
path(X, Y) :- edge(X, Z), path(Z, Y).
/* Is even or odd? */
isodd(0) :- fail.
isodd(1).
isodd(N) :- N > 1, M is N - 1, iseven(M).
iseven(0).
iseven(1) :- fail.
iseven(N) :- N > 0, M is N - 1, isodd(M).
/* Member? */
/* I is only element in list. */
ismember(I, [I]).
/* I is first element in list. */
ismember(I, [I|_]).
/* I is in the tail. */
ismember(I, [_|T]) :- ismember(I, T).
/* Sorted? */
sorted([]).
sorted([_]).
sorted([A,B|T]) :- A =< B, write(A), write(' is <= '), write(B), nl, sorted([B|T]).
Haiku
lang(scheme). lang(c). lang…
perfectlang(X) :- lang(X), fail.
perfectlang(Y). no