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indomain(?Var, ++Method)
a flexible way to assign values to finite domain variables
- Var
- a domain variable or an integer
- Method
- one of the atoms min, max, middle, median, split, interval, random or an integer
Description
This predicate provides a flexible way to assign values to finite
domain variables.
The available methods are:
- min Start the enumeration from the smallest value upwards.
This behaves like the built-in indomain/1, except that it
removes previously tested values on backtracking.
- max Start the enumeration from the largest value
downwards.
- middle Try the enumeration starting from the middle of the
domain. On backtracking, this chooses alternatively values above and
below the middle value, until all alternatives have been tested.
- median Try the enumeration starting from the median value
of the domain. On backtracking, this chooses alternatively values
above and below the median value, until all alternatives have been
tested.
- split Try the enumeration by splitting the domain
successively into halves until a ground value is reached. This
sometimes can detect failure earlier than the normal enumeration
methods, but enumerates the values in the same order as min.
- interval If the domain consists of several intervals, then
we branch first on the choice of the interval. For one interval, we
use domain splitting.
- random Try the enumeration in a random order. On
backtracking, the previously tested value is removed. This method
uses random/1 to create random numbers, use seed/1
before to make results reproducible.
- Value:integer Like middle, but start with the given integer
Value
- sbds_min Like min, but use sbds_try/2 to make choices (for
use in conjunction with the SBDS symmetry breaking library).
- sbds_max Like max, but use sbds_try/2 to make choices (for
use in conjunction with the SBDS symmetry breaking library).
- sbds_middle Like middle, but use sbds_try/2 to make choices
(for use in conjunction with the SBDS symmetry breaking library).
- sbds_median Like median, but use sbds_try/2 to make choices
(for use in conjunction with the SBDS symmetry breaking library).
- sbds_random Like random, but use sbds_try/2 to make choices
(for use in conjunction with the SBDS symmetry breaking library).
- sbds(Value:integer) Like Value:integer, but use sbds_try/2
to make choices (for use in conjunction with the SBDS symmetry breaking
library).
On backtracking, all methods first remove the previously tested value
before choosing a new one. This sometimes can have a huge impact on
the constraint propagation, and normally does not cause much overhead,
even if no additional propagation occurs.
Fail Conditions
No
Resatisfiable
yes
Examples
top:-
X :: 1..10,
indomain(X,min),
write(X),put(32),
fail.
top.
% writes 1 2 3 4 5 6 7 8 9 10
top:-
X :: 1..10,
indomain(X,max),
write(X),put(32),
fail.
top.
% writes 10 9 8 7 6 5 4 3 2 1
top:-
X :: 1..10,
indomain(X,middle),
write(X),put(32),
fail.
top.
% writes 5 6 4 7 3 8 2 9 1 10
top:-
X :: 1..10,
indomain(X,median),
write(X),put(32),
fail.
top.
% writes 5 6 4 7 3 8 2 9 1 10
top:-
X :: 1..10,
indomain(X,3),
write(X),put(32),
fail.
top.
% writes 3 4 2 5 1 6 7 8 9 10
top:-
X :: 1..10,
indomain(X,split),
write(X),put(32),
fail.
top.
% writes 1 2 3 4 5 6 7 8 9 10
top:-
X :: 1..10,
indomain(X,random),
write(X),put(32),
fail.
top.
% writes for example 5 3 7 6 8 1 2 10 9 4
See Also
search / 6, fd : indomain / 1, fdplex : indomain / 1, ic : indomain / 1, ic_symbolic : indomain / 1, random / 1, seed / 1, fd_sbds : sbds_try / 2, ic_sbds : sbds_try / 2