fpg1503/generic-zebra-solver

🎹 A Prolog solver using CLPFD to any logic puzzle like the Zebra Puzzle

Generic Zebra Solver

A Prolog solver using CLPFD to any logic puzzle like the Zebra Puzzle

Specification

Solver Predicate

The predicate solver(+Filename, -Solution) is satisfied when Solution is the solution of the logic puzzle specified by the file named Filename.

Puzzle definition

A puzzle is defined by a .prob file which consists in a list of domains and a list of constraints. There must be a blank line between the list of domains and the list of constraints.

List of Domains

The domain list consists of the domain name followed by a colon and the list of possible values separated by commas. Each domains must be in a single line. All domains must have the same nember of possible values.

The domain color with the colors blue, red, and black can be represented as follows:

color: blue, red, black

analogously nacionality can be defined as:

nacionality: german, spanish, italian

List of Constraints

A list of contraints consists of several constraints, one per line followed by an empty line.

Each constraint is represented by a logical expression which, by definition, is true. This expression is one of

• LHS = RHS
• LHS < RHS
• LHS > RHS

where LHS and RHS are mathematical expressions.

A constraint can also be

• LHS or RHS where LHS and RHS are one of the logical expressions defined above.

For simplicity sake let's define a value as either an integer or a variable. With that in mind a mathematical expression is one of

• value
• value + value
• value - value
• abs(mathematical_expression)

Some sample constraints are:

spanish = red + 1
german = blue
italian = 2
german = 3 or black - 2 = abs(red - blue)

Solution definition

Solution is a Prolog list of variable assignments. The first house is assumed to be number one.

Variable Assignment

A variable assignment consists of the functor c with arity 2 where the first argument is the variable name and the second is the its value, for example

[c(italian,2),c(spanish,3),c(german,1),c(black,3),c(red,2),c(blue,1)]

Contributing

Please fell free to fork, and create issues for any bugs/improvements/doubts.