c  go  java  js  lua  py  vbs  rkt  scm  pro  

Here is some information about using the rmsDSL for permutations for Prolog. This system helps in generating permutations for finite domains to help solve problems involving finite domains.

It is a DSL (Domain Specific Language) system in that the source code allows the possibility of generating other languages at some future time using the same specification.

A finite domain is a domain that is not infinite. It is finite.

Here are some examples of finite domains.

• The digits from 0 to 9.
• The colors "red", "green" and "blue".

Selecting "New" currently provides a starter source code such as the following.

Here is the DSL code.
dsl permute for "pro" domain bit values 0 1 names X1 X2 domain color values "red" "green" "blue" names C1 C2 C3 end
In this case, the names "A", "B" and "C" are to be permuted using the values 1, 2 and 3.

Here is the grammar and syntax diagram for the permutation DSL.

Here is the associated EBNF (Extended Backus Naur Form) grammar.

Note the following.

• The domain should start with a lowercase letter (i.e., Prolog atom).
• All names should start with an uppercase letter (i.e., Prolog variable).

Any line starting with "//" is a comment line and is ignored. Values can be numbers (integers) or strings in double quotes.

If there are more names than values then, since each name must be different, no output would ever be generated (an error message is generated).

Here is the associated EBNF syntax diagram(s).

The "Run" button generates a TuProlog Prolog program to generate and output the requested permutations.

In practice, such as in solving puzzles, only part of the program is needed, but the entire program is generated so one can easily verify that it works.

In practice, the relevant output below would be copied to a Prolog program/script and constraints would be added to prune the search.

Here is the output of the DSL code.
prints([]):- nl. prints([X|Rest]):- print(X), prints(Rest). bit(0). bit(1). color("red"). color("green"). color("blue"). dif(X,Y):- X \= Y. go:- bit(X1), bit(X2), dif(X2,X1), color(C1), color(C2), dif(C2,C1), color(C3), dif(C3,C2), dif(C3,C1), % warning: add constraints or a lot of output could be generated. prints([]), prints(["bit:"," X1=",X1," X2=",X2]), prints(["color:"," C1=",C1," C2=",C2," C3=",C3]), fail. :- solve(go).

Here is the generated program from above.

Here is the Prolog code.
prints([]):- nl. prints([X|Rest]):- print(X), prints(Rest). bit(0). bit(1). color("red"). color("green"). color("blue"). dif(X,Y):- X \= Y. go:- bit(X1), bit(X2), dif(X2,X1), color(C1), color(C2), dif(C2,C1), color(C3), dif(C3,C2), dif(C3,C1), % warning: add constraints or a lot of output could be generated. prints([]), prints(["bit:"," X1=",X1," X2=",X2]), prints(["color:"," C1=",C1," C2=",C2," C3=",C3]), fail. :- solve(go).
Note that in practice one needs only part of the output and can select that part as desired.

• The number of permutations of 2 objects is 2! = 2*1 = 2.
• The number of permutations of 3 objects is 3! = 3*2*1 = 6.

Below are all 12 permutations of the bits 0 to 1 and the colors "red", "green" and "blue".

Note that in Prolog it often requires assert and retract to output a numbered list in the presence of fail.

Here is the output of the Prolog code.
bit: X1=0 X2=1 color: C1=red C2=green C3=blue bit: X1=0 X2=1 color: C1=red C2=blue C3=green bit: X1=0 X2=1 color: C1=green C2=red C3=blue bit: X1=0 X2=1 color: C1=green C2=blue C3=red bit: X1=0 X2=1 color: C1=blue C2=red C3=green bit: X1=0 X2=1 color: C1=blue C2=green C3=red bit: X1=1 X2=0 color: C1=red C2=green C3=blue bit: X1=1 X2=0 color: C1=red C2=blue C3=green bit: X1=1 X2=0 color: C1=green C2=red C3=blue bit: X1=1 X2=0 color: C1=green C2=blue C3=red bit: X1=1 X2=0 color: C1=blue C2=red C3=green bit: X1=1 X2=0 color: C1=blue C2=green C3=red

The DSL for Prolog permutations can be useful in creating the facts and rules needed to obtain permutations for various parts of puzzle solutions.

---