Chapter 2

Slide, Data objects, Figure 2.1

Slide, Atoms

Slide, Anonymous variables
vi ch1.pl, and uncomment has_a_child with singleton variable
?- consult( 'ch1.pl').
vi ch1.pl, and uncomment has_a_child with anonymous variable
?- consult( 'ch1.pl').
Avoid singleton variables.

Slide, Structures
Slide, Name, Arity

Slide, Terms

Slide, Figure 2.3
Point

Reveal:
Segment
Triangle

Slide, Fiogure 2.4

Slide, Figure 2.5
Discuss representation

Slide, Figure 2.6
Discuss representation
Reveal (c) and (d)

Slide, Figure 2.7
Demo the caption

Slide, Figure 2.8
ch2.pl, scroll to Figure 2.8
?- [ch2].
is a shortcut for consult

Demo
?- vertical( seg( point( 1, 1), point( 1, 2))).
?- vertical( seg( point( 1, 1), point( 2, Y))).
?- horizontal( seg( point( 1, 1), point( 2, Y))).
?- vertical( seg(point (2,3)), P)).

Slide, Matching

Demo
?- a( b, c) = a( b, c).
?- a( B, c) = a( b, c).
?- a( b, c) = a( B, C).
?- a( B, c) = a( D, c).
?- a( B, C) = a( b, b).
?- a( b, c( d, e)) = a( F, G).
?- a( b, c( d( e, f), g( h))) = a( F, c( I, g( J))).
?- a( B, C, D) = a( E, f, G), a( B, C, D) = a( e, F, G).

?- date( D, M, 2001) = date( D1, may, Y1).
?- date( D, M, 2001) = date( D1, may, Y1),
   date( D, M, 2001) = date( 15, M, Y).

Experiment
?- a = 5.
?- X = 5.
?- 5 = X.
?- X = Y, Y = a.
etc.

Slide, Definitions
; only used occasionally.

Slide, Declarative meaning
Note: the program is the database.
The goal G is a query.

Slide, Procedural meaning
Analogous to knowing how to program with recursion and understanding its implementation
on the run-time stack.

Slides
The bear, elephant, cat example is figure 2.10 in the book.

Slide
Pseudocode of unification algorithm

Slides, Reordering clauses and goals