Class: Gecode::Constraints::IntEnum::Extensional::RegexpConstraint
- Inherits:
-
Constraint
- Object
- Constraint
- Gecode::Constraints::IntEnum::Extensional::RegexpConstraint
- Defined in:
- lib/gecoder/interface/constraints/int_enum/extensional.rb
Overview
Describes a regexp constraint, which constrains the enumeration of integer variables to match a specified regexp in the integer domain. Neither negation nor reification is supported.
Regexp syntax
The regular expressions are specified using arrays, integers and a few methods provided by Model. Arrays are used to group the integers in sequences that must be matched. The following array describes a regular expression matching a 1 followed by a 7.
[1, 7]
Arrays can be nested or left out when not needed. I.e. the above is semantically equal to
[[[1], 7]]
A couple of methods provided by Model are used to express patterns beyond mere sequences:
- Model#repeat
-
Used for specifying patterns that include patterns that may be repeated a given number of times. The number of times to repeat a pattern can be specified using a lower and upper bound, but the bounds can be omitted to for instance allow an expression to be repeated any number of times.
- Model#any
-
Used for specifying alternatives.
Additionally Model#at_least_once and Model#at_most_once are provided as convenience methods.
Examples
# Matches 1 followed by any number of 2s.
[1, repeat(2)]
# Semantically the same as above. It just has a bunch of
# needless brackets thrown in.
[[1], [repeat([2])]]
# Matches 1 followed by [a 2 followed by a 3] at least two times.
# Matches e.g. 1, 2, 3, 2, 3
[1, repeat([2, 3], 2)]
# Matches between one and two [2 followed by [at least three 1]]
# followed by between three and four 3. Matches e.g.
# 2, 1, 1, 1, 2, 1, 1, 1, 3, 3, 3
[repeat([2, repeat(1, 3], 1, 2), repeat(3, 3, 4)]
# Matches [1, 2 or 3] followed by 4. Matches e.g. 2, 4
[any(1, 2, 3), 4]
# Matches 0 followed by [[1 followed by 2] or [3 followed by 5]].
# Matches e.g. 0, 1, 2 as well as 0, 3, 5
[0, any([1, 2], [3, 5])]
# Matches 0 followed by [[[1 followed by 7] at least two times]
# or [[8, 9], at most two times]. Matches e.g.
# 0, 1, 7, 1, 7, 1, 7 as well as 0, 8, 9
[0, any(repeat([1, 7], 2), repeat([8, 9], 0, 2)]
# Matches 0 followed by at least one 1.
[0, at_least_once(1)]
# Exactly the same as the above.
[0, repeat(1, 1)]
# Matches 0 followed by at least one [[1 followed by 7] or [3
# followed by 2]]. Matches e.g. 0, 1, 7, 3, 2, 1, 7
[0, at_least_once(any([1, 7], [3, 2]]
# Matches 0 followed by at either [[1 followed by 7] at least once]
# or [[3 followed by 2] at least once]. Matches e.g.
# 0, 1, 7, 1, 7 but does _not_ match 0, 1, 7, 3, 2, 1, 7
[0, any(at_least_once([1, 7]), at_least_once([3, 2])]
# Matches 0, followed by at most one 1. Matches 0 as well as
# 0, 1
[0, at_most_once(1)]
# Exactly the same as the above.
[0, repeat(1, 0, 1)]
Example
# Constrains the two integer variables in +numbers+ to have
# values 1 and 7.
numbers.must.match [1, 7]
# Constrains the integer variables in +numbers+ to contain the
# value 47 followed by 11, with all other values set to -1.
numbers.must.match [repeat(-1), 47, 11, repeat(-1)]
# Constrains exactly three of the integer variables in +numbers+ to
# contain 47 or 11, each followed by at least two
# variables set to -1. All other variables are constrained to
# equal -1.
numbers.must.match repeat([repeat(-1), any(11, 47),
repeat(-1, 2)], 3, 3)
Instance Method Summary collapse
Methods inherited from Constraint
Constructor Details
This class inherits a constructor from Gecode::Constraints::Constraint