Prolog

Shen has a Prolog notation consistent with the rest of Shen which uses defprolog. Here are the member, reverse and append functions in Shen Prolog.

(48-) (defprolog member
X [X | _] <--;
X [_ | Y] <-- (member X Y);)
member

(49-)(defprolog rev
[] [] <--;
[X | Y] Z <-- (rev Y W) (conc W [X] Z);)
rev

(50-)(defprolog conc
[] X X <--;
[X | Y] Z [X | W] <-- (conc Y Z W);)
conc

(51-) (prolog? (member 1 [1 2]))
true

(52-) (prolog? (member 0 [1 2]))
false

(53-) (prolog? (member X [1 2]))
true

(54-) (prolog? (member X [1 2]) (return X))
1

(55-) (prolog? (rev [1 2] X) (return X))
[2 1]

Further Reading

• Shen Official Standard