- Documentation
- Reference manual
- The SWI-Prolog library
- library(aggregate): Aggregation operators on backtrackable predicates
- library(ansi_term): Print decorated text to ANSI consoles
- library(apply): Apply predicates on a list
- library(assoc): Association lists
- library(broadcast): Broadcast and receive event notifications
- library(charsio): I/O on Lists of Character Codes
- library(check): Consistency checking
- library(clpb): CLP(B): Constraint Logic Programming over Boolean Variables
- library(clpfd): CLP(FD): Constraint Logic Programming over Finite Domains
- library(clpqr): Constraint Logic Programming over Rationals and Reals
- library(csv): Process CSV (Comma-Separated Values) data
- library(dcg/basics): Various general DCG utilities
- library(dcg/high_order): High order grammar operations
- library(debug): Print debug messages and test assertions
- library(dicts): Dict utilities
- library(error): Error generating support
- library(fastrw): Fast reading and writing of terms
- library(gensym): Generate unique symbols
- library(heaps): heaps/priority queues
- library(increval): Incremental dynamic predicate modification
- library(intercept): Intercept and signal interface
- library(iostream): Utilities to deal with streams
- library(listing): List programs and pretty print clauses
- library(lists): List Manipulation
- library(macros): Macro expansion
- library(main): Provide entry point for scripts
- library(nb_set): Non-backtrackable set
- library(www_browser): Open a URL in the users browser
- library(occurs): Finding and counting sub-terms
- library(option): Option list processing
- library(optparse): command line parsing
- library(ordsets): Ordered set manipulation
- library(pairs): Operations on key-value lists
- library(persistency): Provide persistent dynamic predicates
- library(pio): Pure I/O
- library(portray_text): Portray text
- library(predicate_options): Declare option-processing of predicates
- library(prolog_coverage): Coverage analysis tool
- library(prolog_debug): User level debugging tools
- library(prolog_jiti): Just In Time Indexing (JITI) utilities
- library(prolog_trace): Print access to predicates
- library(prolog_versions): Demand specific (Prolog) versions
- library(prolog_xref): Prolog cross-referencer data collection
- library(quasi_quotations): Define Quasi Quotation syntax
- library(random): Random numbers
- library(rbtrees): Red black trees
- library(readutil): Read utilities
- library(record): Access named fields in a term
- library(registry): Manipulating the Windows registry
- library(rwlocks): Read/write locks
- library(settings): Setting management
- library(statistics): Get information about resource usage
- library(strings): String utilities
- library(simplex): Solve linear programming problems
- library(solution_sequences): Modify solution sequences
- library(tables): XSB interface to tables
- library(terms): Term manipulation
- library(thread): High level thread primitives
- library(thread_pool): Resource bounded thread management
- library(ugraphs): Graph manipulation library
- library(url): Analysing and constructing URL
- library(varnumbers): Utilities for numbered terms
- library(yall): Lambda expressions
- The SWI-Prolog library
- Packages
- Reference manual
A.27 library(nb_set): Non-backtrackable set
The library library(nb_set)
defines non-backtrackable
sets, implemented as binary trees. The sets are represented as
compound terms and manipulated using nb_setarg/3.
Non-backtrackable manipulation of data structures is not supported by a
large number of Prolog implementations, but it has several advantages
over using the database. It produces less garbage, is thread-safe,
reentrant and deals with exceptions without leaking data.
Similar to the library(assoc)
library, keys can be any
Prolog term, but it is not allowed to instantiate or modify a term.
One of the ways to use this library is to generate unique values on backtracking without generating all solutions first, for example to act as a filter between a generator producing many duplicates and an expensive test routine, as outlined below:
generate_and_test(Solution) :- empty_nb_set(Set), generate(Solution), add_nb_set(Solution, Set, true), test(Solution).
- empty_nb_set(?Set)
- True if Set is a non-backtrackable empty set.
- add_nb_set(+Key, !Set)
- Add Key to Set. If Key is already a member of Set, add_nb_set/3 succeeds without modifying Set.
- add_nb_set(+Key, !Set, ?New)
- If Key is not in Set and New is unified
to
true
, Key is added to Set. If Key is in Set, New is unified tofalse
. It can be used for many purposes:add_nb_set(+, +, false)
Test membership add_nb_set(+, +, true)
Succeed only if new member add_nb_set(+, +, Var)
Succeed, binding Var - gen_nb_set(+Set, -Key)
- Generate all members of Set on backtracking in the standard order of terms. To test membership, use add_nb_set/3.
- size_nb_set(+Set, -Size)
- Unify Size with the number of elements in Set.
- nb_set_to_list(+Set, -List)
- Unify List with a list of all elements in Set in the standard order of terms (i.e., an ordered list).