Getting Started

February 17, 2019 ยท View on GitHub

Start D-Prolog

$ dprolog
?-

With an initialization file:

$ dprolog -f example/family.pro
?-

?- male(X).
X = bob;
X = tom;
X = jim.

Stop D-Prolog

?- halt.

or input ctrl+c or ctrl+d to stop D-Prolog.

Options

  • -h, --help: Print a help message
  • -v, --version: Print version of dprolog
  • -f, --file=VALUE: Read VALUE as an initialization file
  • --verbose: Print diagnostic output

Example Prolog files

  • example/family.pro
  • example/list.pro
  • example/factorial.pro
  • example/if.pro

Load a file while running

Input a query ?- [<file path>]. while running as follows:

?- [`file.pro`].

?- [`/path/to/file.pro`].

Add rules from the console

Input a query ?- [user]., and you will be able to add rules from the console:

?- [user].
|: hoge(poyo).
|:

Input ctrl+c or ctrl+d to exit from the mode for adding rules.

?- hoge(X).
X = poyo.

Comments

The %-style line comments are supported.

?- X = 1. % This is a comment.
X = 1.

Lists

?- X = [a, b, c].
X = [a, b, c].

?- X = [a | [b, c]].
X = [a, b, c].

Integers and Arithmetic Operations

?- X = 10. % A decimal literal
X = 10.

?- X = 0b1010. % A binary literal
X = 10.

?- X = 0xff. % A hexadecimal literal
X = 255.

?- X is 1 + 2.
X = 3.

?- X = 10, Y is X * X - 1.
X = 10, Y = 99.

?- 10 < 100.
true.

Conjunctions and Disjunctions

$ dprolog -f list.pro

Conjunctions:

?- member(X, [1, 2, 3]), member(X, [3, 4]).
X = 3;
false.

Disjunctions:

?- member(X, [1, 2, 3]); member(X, [3, 4]).
X = 1;
X = 2;
X = 3;
X = 3;
X = 4;
false.

Conjuctions and disjunctions:

?- member(X, [1, 2, 3]); member(X, [3, 4]), X > 3.
X = 1;
X = 2;
X = 3;
X = 4.

?- (member(X, [1, 2, 3]); member(X, [3, 4])), X > 3.
X = 4.

Cut Operator

?- X = 1; X = 2.
X = 1;
X = 2.

?- X = 1, !; X = 2.
X = 1.

Load example/if.pro, then

?- if(true, X = 1, X = 2).
X = 1.

?- if(false, X = 1, X = 2).
X = 2.

If you want to know more about D-Prolog, see Specification.