I could not find division (/) symbol on this page of CLP(FD): http://www.swi-prolog.org/man/clpfd.html
Also this simple code give error:
:-use_module(library(clpfd)).
afn(A,B,C):-
C #= B / A.
?- afn(23, 56, C).
ERROR: Domain error: `clpfd_expression' expected, found `56/23'
Where is the problem and how can this be solved? Thanks.
In ISO Prolog (/)/2 yields a float result. SWI-Prolog is not ISO compliant here, it casts to an integer where possible. But basically (/)/2 is viewed as an operation between machine real numbers, that gives a new approximated machine real number.
On the other hand CLP(FD) works only with integers. Therefore, I guess, this is the reason that CLP(FD) usually don't support the (/)/2 operator. On the otherhand the div operator (//)/2 from ISO Prolog, works also for CLP(FD). Supported are:
Expr // Expr Truncated integer division
Expr div Expr Floored integer division
Here is an example run:
Welcome to SWI-Prolog (threaded, 64 bits, version 8.1.4)
?- use_module(library(clpfd)).
true.
?- X #= 100 // Y, Y = 7.
X = 14,
Y = 7.
?- X #= Z // 7, X = 14.
X = 14,
Z in 98..104.
If you have a CLP(FD) without the (//)/2 operator, you can simulate it. Instead of X #= Y//Z, you can write X*Z+R #= Y, 0 #=< R, R #< Z. When negative arguments are involved you need a more complex formula.
Here are some example runs that show that this approach also works:
?- X*Y+R #= 100, 0 #=< R, R #< Y, Y = 7.
X = 14,
Y = 7,
R = 2.
?- X*7+R #= Z, 0 #=< R, R #< 7, X = 14.
X = 14,
R in 0..6,
-98+Z#=R,
Z in 98..104.