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Unit 14: Prolog

?- X is 2 + 2, 3 >= X. Notes
no

?- 3+4 > 3*2.

yes

They can be used in rules also.

Example: Here are two example predicates. One transforms centigrade temperatures to
Fahrenheit, the other verifies if a temperature is below freezing.

c_to_f(C,F) :-
F is C * 9 / 5 + 32.

freezing(F) :-
F =< 32.

Here are some examples of their use.

?- c_to_f(100,X).
X = 212
yes

?- freezing(15).
yes

?- freezing(45).
no

Self Assessment

Fill in the blank:
10. Prolog must be able to manage arithmetic in order to be a ...................... general purpose
programming language.

14.7 Matching

Two terms are defined to match if they are either indistinguishable or if they can be made
indistinguishable by variable instantiation. Instantiating a variable means allocating it a xed
value. Two free variables also match, since they could be instantiated with the similar ground
term.

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