Tutorial by Examples

Many modern Prolog systems are in continuous development and have added new features to address classic shortcomings of the language. Unfortunately, many Prolog textbooks and even teaching courses still introduce only the outdated prolog. This topic is intended to illustrate how modern Prolog has ov...

Traditionally Prolog performed arithmetic using the is and =:= operators. However, several current Prologs offer CLP(FD) (Constraint Logic Programming over Finite Domains) as a cleaner alternative for integer arithmetic. CLP(FD) is based on storing the constraints that apply to an integer value and ...

Some "classic" Prolog textbooks still use the confusing and error-prone failure-driven loop syntax where a fail construct is used to force backtracking to apply a goal to every value of a generator. For example, to print all numbers up to a given limit: fdl(X) :- between(1,X,Y), print(Y),...

Traditionally in Prolog, "functions" (with one output and bound inputs) were written as regular predicates: mangle(X,Y) :- Y is (X*5)+2. This can create the difficulty that if a function-style predicate is called multiple times, it is necessary to "daisy chain" temporary vari...

When programming in Prolog it is not always possible, or desirable, to create predicates which unify for every possible combination of parameters. For example, the predicate between(X,Y,Z) which expresses that Z is numerically between X and Y. It is easily implemented in the cases where X, Y, and Z ...