library

Prolog files

aggregate.pl
aggregate/3	Aggregate bindings in Goal according to Template.
aggregate/4	Aggregate bindings in Goal according to Template.
aggregate_all/3	Aggregate bindings in Goal according to Template.
aggregate_all/4	Aggregate bindings in Goal according to Template.
foldall/4	Use Folder to fold V0 to V using all answers of Goal.
foreach/2	True when the conjunction of instances of Goal created from solutions for Generator is true.
free_variables/4	Find free variables in bagof/setof template.
safe_meta/2	Declare the aggregate meta-calls safe.
ansi_term.pl  -- Print decorated text to ANSI consoles
apply.pl  -- Apply predicates on a list
apply_macros.pl  -- Goal expansion rules to avoid meta-calling
arithmetic.pl  -- Extensible arithmetic
assoc.pl
assoc_to_keys/2	True if Keys is the list of keys in Assoc.
assoc_to_list/2	Translate Assoc to a list Pairs of Key-Value pairs.
assoc_to_values/2	True if Values is the list of values in Assoc.
del_assoc/4	True if Key-Value is in Assoc0.
del_max_assoc/4	True if Key-Value is in Assoc0 and Key is the greatest key.
del_min_assoc/4	True if Key-Value is in Assoc0 and Key is the smallest key.
empty_assoc/1	Is true if Assoc is the empty association list.
gen_assoc/3	True if Key-Value is an association in Assoc.
get_assoc/3	True if Key-Value is an association in Assoc.
get_assoc/5	True if Key-Val0 is in Assoc0 and Key-Val is in Assoc.
is_assoc/1	True if Assoc is an association list.
list_to_assoc/2	Create an association from a list Pairs of Key-Value pairs.
map_assoc/2	True if Pred(Value) is true for all values in Assoc.
map_assoc/3	Map corresponding values.
max_assoc/3	True if Key-Value is in Assoc and Key is the largest key.
min_assoc/3	True if Key-Value is in assoc and Key is the smallest key.
ord_list_to_assoc/2	Assoc is created from an ordered list Pairs of Key-Value pairs.
put_assoc/4	Assoc is Assoc0, except that Key is associated with Value.
atom.pl  -- Operations on atoms
backcomp.pl
$apropos_match/2	True if Needle is a sub atom of Haystack.
$arch/2
$argv/1
$declare_module/3	Used in triple20 particle library.
$home/1
$module/2
$set_prompt/1	Set the prompt for the toplevel.
$sig_atomic/1	Execute Goal without processing signals.
$strip_module/3	This used to be an internal predicate.
$version/1
C/3	Used to be generated by DCG.
at_initialization/1	Register goal only to be run if a saved state is restored.
call_cleanup/3	Call Cleanup with an indication of the reason unified to Catcher.
checklist/2
concat/3
concat_atom/2	Concatenate a list of atomic values to an atom.
concat_atom/3	Concatenate a list of atomic values to an atom, inserting Separator between each consecutive elements.
convert_time/2	Convert a time-stamp as obtained though get_time/1 into a textual representation using the C-library function ctime().
convert_time/8	Convert a time stamp, provided by get_time/1, time_file/2, etc.
current_module/2	True if Module is a module loaded from File.
current_mutex/3
current_thread/2
displayq/1	Write term ignoring operators and quote atoms.
displayq/2	Write term ignoring operators and quote atoms.
eval_license/0
export_list/2	Module exports the predicates of List.
feature/2	Control Prolog flags.
flush/0
free_variables/2	Return a list of unbound variables in Term.
hash/1	Demands PredInd to be indexed using a hash-table.
hash_term/2	If Term is ground, Hash is unified to an integer representing a hash for Term.
index/1	Prepare the predicate indicated by Head for multi-argument indexing.
lock_predicate/2
merge/3	Merge the ordered sets List1 and List2 into a new ordered list.
merge_set/3	Merge the ordered sets Set1 and Set2 into a new ordered set without duplicates.
message_queue_size/2	True if Queue holds Size terms.
proper_list/1	Old SWI-Prolog predicate to check for a list that really ends in a [].
read_clause/1
read_clause/2
read_history/6
read_pending_input/3
read_variables/2
read_variables/3
set_base_module/1	Set the default module from which we inherit.
set_feature/2	Control Prolog flags.
setup_and_call_cleanup/3	Call Cleanup once after Goal is finished.
setup_and_call_cleanup/4	Call Cleanup once after Goal is finished, with Catcher unified to the reason.
sformat/2
sformat/3
string_to_atom/2	Bi-directional conversion between string and atom.
string_to_list/2	Bi-directional conversion between a string and a list of character codes.
sublist/3	Succeeds if List2 unifies with a list holding those terms for which call(Goal, Elem) succeeds.
substring/4	Predecessor of sub_string using 1-based Offset.
sumlist/2	True when Sum is the list of all numbers in List.
thread_at_exit/1	Register Goal to be called when the calling thread exits.
trie_insert_new/3
unlock_predicate/2
write_ln/1
base32.pl  -- Base32 encoding and decoding
base64.pl  -- Base64 encoding and decoding
broadcast.pl  -- Event service
charsio.pl  -- I/O on Lists of Character Codes
check.pl  -- Consistency checking
codesio.pl  -- I/O on Lists of Character Codes
coinduction.pl  -- Co-Logic Programming
csv.pl  -- Process CSV (Comma-Separated Values) data
ctypes.pl  -- Character code classification
date.pl  -- Process dates and times
debug.pl  -- Print debug messages and test assertions
dialect.pl  -- Support multiple Prolog dialects
dicts.pl  -- Dict utilities
dif.pl  -- The dif/2 constraint
edinburgh.pl  -- Some traditional Edinburgh predicates
edit.pl  -- Editor interface
error.pl
exceptions.pl  -- Exception classification
fastrw.pl
fast_read/1	The next term is read from current standard input and is unified with Term.
fast_write/1	Output Term in a way that fast_read/1 and fast_read/2 will be able to read it back.
fast_write_to_string/3	Perform a fast-write to the difference-slist String\Tail.
gensym.pl
gensym/2	Generate <Base>1, <Base>2, etc atoms on each subsequent call.
reset_gensym/0	Reset gensym for all registered keys.
reset_gensym/1	Restart generation of identifiers from Base at <Base>1.
git.pl  -- Run GIT commands
hashtable.pl
ht_del/3	Delete Key-Value from HT.
ht_gen/3	True when Key-Value is in HT.
ht_get/3	True when Key is in HT and associated with Value.
ht_is_hashtable/1	True when HT is a hash table.
ht_keys/2	True when Keys is an ordered set of all keys in HT.
ht_new/1	Create a new hash table.
ht_pairs/2	True when Pairs and HT represent the same association.
ht_put/3	Add a Key-Value to HT.
ht_put/5	Add Key-Value to HT.
ht_put_new/3	As ht_put/3, but fails if Key is already in HT instead of updating the associated value.
ht_size/2	True when Size is the number of key-value pairs in HT.
ht_update/4	True when HT holds Key-Old before and Key-New after this call.
heaps.pl  -- heaps/priority queues
help.pl  -- Text based manual
increval.pl  -- Incremental dynamic predicate modification
intercept.pl
intercept/3	Run Goal as call/1.
intercept/4	Similar to intercept/3, but the copy of Handler is called as call(Copy,Arg), which allows passing large context arguments or arguments subject to unification or destructive assignment.
intercept_all/4	True when List contains all instances of Template that have been sent using send_signal/1 where the argument unifies with Ball.
nb_intercept_all/4	As intercept_all/4, but backtracing inside Goal does not reset List.
send_signal/1	If this predicate is called from a sub-goal of intercept/3, execute the associated Handler of the intercept/3 environment.
send_silent_signal/1	As send_signal/1, but succeed silently if there is no matching intercept environment.
iostream.pl  -- Utilities to deal with streams
close_any/1	Execute the Close closure returned by open_any/5.
open_any/5	Establish a stream from Specification that should be closed using Close, which can either be called or passed to close_any/1.
lazy_lists.pl
lazy_engine_next/4	Lazy list iterator for engines.
lazy_findall/3	True when List is a lazy list containing the instantiations for Template for each answer of Goal.
lazy_findall/4	True when List is a lazy list containing the instantiations for Template for each answer of Goal.
lazy_get_codes/4	Lazy list iterator to get character codes from a stream.
lazy_list/2	Create a lazy list from a callback.
lazy_list/3	Create a lazy list where the next element is defined by.
lazy_list_iterator/4	Directive to create a lazy list iterator from a predicate that gets a single next value.
lazy_list_length/2	True if Len is the length of the materialized lazy list.
lazy_list_materialize/1	Materialize the lazy list.
lazy_message_queue/4	Lazy list iterator for message queues.
lazy_read_lines/4	Lazy list iterator to read lines from Stream.
lazy_read_terms/4	Turn a stream into a lazy list of Prolog terms.
listing.pl  -- List programs and pretty print clauses
listing/0	Lists all predicates defined in the calling module.
listing/1	List matching clauses.
listing/2	List matching clauses.
portray_clause/1	Portray `Clause' on the current output stream.
portray_clause/2	Portray `Clause' on the current output stream.
portray_clause/3	Portray `Clause' on the current output stream.
lists.pl
append/2	Concatenate a list of lists.
append/3	List1AndList2 is the concatenation of List1 and List2.
clumped/2	Pairs is a list of Item-Count pairs that represents the run length encoding of Items.
delete/3	Delete matching elements from a list.
flatten/2	Is true if FlatList is a non-nested version of NestedList.
intersection/3	True if Set3 unifies with the intersection of Set1 and Set2.
is_set/1	True if Set is a proper list without duplicates.
last/2	Succeeds when Last is the last element of List.
list_to_set/2	True when Set has the same elements as List in the same order.
max_list/2	True if Max is the largest number in List.
max_member/2	True when Max is the largest member in the standard order of terms.
max_member/3	True when Max is the largest member according to Pred, which must be a 2-argument callable that behaves like (@=<)/2.
member/2	True if Elem is a member of List.
min_list/2	True if Min is the smallest number in List.
min_member/2	True when Min is the smallest member in the standard order of terms.
min_member/3	True when Min is the smallest member according to Pred, which must be a 2-argument callable that behaves like (@=<)/2.
nextto/3	True if Y directly follows X in List.
nth0/3	True when Elem is the Index'th element of List.
nth0/4	Select/insert element at index.
nth1/3	Is true when Elem is the Index'th element of List.
nth1/4	As nth0/4, but counting starts at 1.
numlist/3	List is a list [Low, Low+1, ... High].
permutation/2	True when Xs is a permutation of Ys.
prefix/2	True iff Part is a leading substring of Whole.
proper_length/2	True when Length is the number of elements in the proper list List.
reverse/2	Is true when the elements of List2 are in reverse order compared to List1.
same_length/2	Is true when List1 and List2 are lists with the same number of elements.
select/3	Is true when List1, with Elem removed, results in List2.
select/4	Select from two lists at the same position.
selectchk/3	Semi-deterministic removal of first element in List that unifies with Elem.
selectchk/4	Semi-deterministic version of select/4.
subseq/3	Is true when SubList contains a subset of the elements of List in the same order and Complement contains all elements of List not in SubList, also in the order they appear in List.
subset/2	True if all elements of SubSet belong to Set as well.
subtract/3	Delete all elements in Delete from Set.
sum_list/2	Sum is the result of adding all numbers in List.
union/3	True if Set3 unifies with the union of the lists Set1 and Set2.
main.pl
argv_options/3	Parse command line arguments.
argv_options/4	As argv_options/3 in guided mode, Currently this version allows parsing argument options throwing an exception rather than calling halt/1 by passing an empty list to ParseOptions.
argv_usage/1	Use print_message/2 to print a usage message at Level.
cli_debug_opt_help/2	Implements opt_type/3, opt_help/2 and opt_meta/2 for debug arguments.
cli_debug_opt_meta/2	Implements opt_type/3, opt_help/2 and opt_meta/2 for debug arguments.
cli_debug_opt_type/3	Implements opt_type/3, opt_help/2 and opt_meta/2 for debug arguments.
cli_enable_development_system/0	Re-enable the development environment.
cli_parse_debug_options/2	Parse certain commandline options for debugging and development purposes.
main/0	Call main/1 using the passed command-line arguments.
make.pl
make/0	Reload all source files that have been changed since they were loaded.
make_reload_file/1	Reload file into the proper module.
modules.pl  -- Module utility predicates
nb_set.pl  -- Non-backtrackable sets
occurs.pl  -- Finding and counting sub-terms
operators.pl
pop_operators/0	Revert all changes to the operator table realised since the last push_operators/1.
pop_operators/1	Reset operators as pushed by push_operators/2.
push_op/3	As op/3, but this call must appear between push_operators/1 and pop_operators/0.
push_operators/1	Installs the operators from New, where New is a list of op(Prec, Type, :Name).
push_operators/2	Installs the operators from New, where New is a list of op(Prec, Type, :Name).
option.pl  -- Option list processing
optparse.pl  -- command line parsing
ordsets.pl  -- Ordered set manipulation
oset.pl
oset_addel/3	Ordered set element addition.
oset_delel/3	Ordered set element deletion.
oset_diff/3	Ordered set difference.
oset_dint/2	Distributed intersection.
oset_dunion/2	Distributed union.
oset_int/3	ordered set intersection.
oset_is/1	check that OSet in correct format (standard order).
oset_power/2	True when PSet is the powerset of Set.
oset_union/3	Union is the union of OSet1 and OSet2.
pairs.pl
group_pairs_by_key/2	Group values with equivalent (==/2) consecutive keys.
map_list_to_pairs/3	Create a Key-Value list by mapping each element of List.
pairs_keys/2	Remove the values from a list of Key-Value pairs.
pairs_keys_values/3	True if Keys holds the keys of Pairs and Values the values.
pairs_values/2	Remove the keys from a list of Key-Value pairs.
transpose_pairs/2	Swap Key-Value to Value-Key.
persistency.pl
current_persistent_predicate/1	True if PI is a predicate that provides access to the persistent database DB.
db_assert/1	Assert Term into the database and record it for persistency.
db_attach/2	Use File as persistent database for the calling module.
db_attached/1	True if the context module attached to the persistent database File.
db_detach/0	Detach persistency from the calling module and delete all persistent clauses from the Prolog database.
db_retract/1	Retract terms from the database one-by-one.
db_retractall/1	Retract all matching facts and do the same in the database.
db_sync/1	Synchronise database with the associated file.
db_sync_all/1	Sync all registered databases.
persistent/1	Declare dynamic database terms.
pio.pl  -- Pure I/O
portray_text.pl
portray_text/1	Switch portraying on or off.
set_portray_text/2	Set options for portraying.
set_portray_text/3	Set options for portraying.
pprint.pl  -- Pretty Print Prolog terms
predicate_options.pl
assert_predicate_options/4	As predicate_options(:PI, +Arg, +Options).
check_predicate_option/3	Verify predicate options at runtime.
check_predicate_options/0	Analyse loaded program for erroneous options.
check_predicate_options/1	Verify calls to predicates that have options in all clauses of the predicate indicated by PredicateIndicator.
current_option_arg/2	True when Arg of PI processes predicate options.
current_predicate_option/3	True when Arg of PI processes Option.
current_predicate_options/3	True when Options is the current active option declaration for PI on Arg.
derive_predicate_options/0	Derive new predicate option declarations.
derived_predicate_options/1	Derive predicate option declarations for a module.
derived_predicate_options/3	Derive option arguments using static analysis.
predicate_options/3	Declare that the predicate PI processes options on Arg.
retractall_predicate_options/0	Remove all dynamically (derived) predicate options.
prolog_autoload.pl  -- Autoload all dependencies
autoload_all/0	Force all necessary autoloading to be done now.
autoload_all/1	Force all necessary autoloading to be done now.
prolog_breakpoints.pl  -- Manage Prolog break-points
prolog_clause.pl
prolog_code.pl  -- Utilities for reasoning about code
prolog_codewalk.pl  -- Prolog code walker
prolog_colour.pl  -- Prolog syntax colouring support.
prolog_config.pl  -- Provide configuration information
prolog_coverage.pl  -- Coverage analysis tool
prolog_debug.pl  -- User level debugging tools
prolog_format.pl
format_spec/2	Parse a format string.
format_spec/3	DCG for parsing format strings.
format_types/2	True when Format requires an argument list with terms of the type specified by Types.
prolog_history.pl
prolog_history/1	Execute Action on the history.
prolog_jiti.pl  -- Just In Time Indexing (JITI) utilities
prolog_metainference.pl
infer_meta_predicate/2	True when MetaSpec is a meta-predicate specifier for the predicate Head.
inferred_meta_predicate/2	True when MetaSpec is an inferred meta-predicate specification for Head.
prolog_pack.pl  -- A package manager for Prolog
prolog_profile.pl
profile/1	Run once(Goal) under the execution profiler.
profile/2	Run once(Goal) under the execution profiler.
profile_data/1	Gather all relevant data from profiler.
profile_procedure_data/2	Collect data for Pred.
show_profile/1	Display last collected profiling data.
prolog_source.pl  -- Examine Prolog source-files
prolog_stack.pl  -- Examine the Prolog stack
prolog_trace.pl  -- Print access to predicates
prolog_versions.pl  -- Demand specific (Prolog) versions
prolog_wrap.pl
current_predicate_wrapper/4	True if Head is wrapped with Body.
unwrap_predicate/2	Remove the outermost wrapper whose name unifies with Name.
wrap_predicate/4	Wrap the predicate referenced by Head using Body.
prolog_xref.pl  -- Prolog cross-referencer data collection
pure_input.pl
lazy_list_character_count/3	True when CharCount is the current character count in the Lazy list.
lazy_list_location/3	Determine current (error) location in a lazy list.
phrase_from_file/2	Process the content of File using the DCG rule Grammar.
phrase_from_file/3	As phrase_from_file/2, providing additional Options.
phrase_from_stream/2	Run Grammer against the character codes on Stream.
stream_to_lazy_list/2	Create a lazy list representing the character codes in Stream.
syntax_error/3	Throw the syntax error Error at the current location of the input.
qsave.pl  -- Save current program as a state or executable
quasi_quotations.pl
phrase_from_quasi_quotation/2	Process the quasi quotation using the DCG Grammar.
quasi_quotation_syntax/1	Declare the predicate SyntaxName/4 to implement the the quasi quote syntax SyntaxName.
quasi_quotation_syntax_error/1	Report syntax_error(Error) using the current location in the quasi quoted input parser.
with_quasi_quotation_input/3	Process the quasi-quoted Content using Stream parsed by Goal.
quintus.pl  -- Quintus compatibility
random.pl
getrand/1	Query/set the state of the random generator.
maybe/0	Succeed/fail with equal probability (variant of maybe/1).
maybe/1	Succeed with probability P, fail with probability 1-P.
maybe/2	Succeed with probability K/N (variant of maybe/1).
random/1	Binds R to a new random float in the open interval (0.0,1.0).
random/3	Generate a random integer or float in a range.
random_between/3	Binds R to a random integer in [L,U] (i.e., including both L and U).
random_member/2	X is a random member of List.
random_numlist/4	Unify List with an ascending list of integers between L and U (inclusive).
random_perm2/4	Does X=A,Y=B or X=B,Y=A with equal probability.
random_permutation/2	Permutation is a random permutation of List.
random_select/3	Randomly select or insert an element.
random_subseq/3	Selects a random subsequence Subseq of List, with Complement containing all elements of List that were not selected.
randseq/3	S is a list of K unique random integers in the range 1..N.
randset/3	S is a sorted list of K unique random integers in the range 1..N.
setrand/1	Query/set the state of the random generator.
rbtrees.pl  -- Red black trees
readutil.pl  -- Read utilities
record.pl  -- Access compound arguments by name
sandbox.pl  -- Sandboxed Prolog code
settings.pl
convert_setting_text/3	Converts from textual form to Prolog Value.
current_setting/1	True if Setting is a currently defined setting.
env/2	Evaluate environment variables on behalf of arithmetic expressions.
env/3	Evaluate environment variables on behalf of arithmetic expressions.
list_settings/0	List settings to current_output.
list_settings/1	List settings to current_output.
load_settings/1	Load local settings from File.
load_settings/2	Load local settings from File.
restore_setting/1	Restore the value of setting Name to its default.
save_settings/0	Save modified settings to File.
save_settings/1	Save modified settings to File.
set_setting/2	Change a setting.
set_setting_default/2	Change the default for a setting.
setting/2	True when Name is a currently defined setting with Value.
setting/4	Define a setting.
setting_property/2	Query currently defined settings.
shlib.pl  -- Utility library for loading foreign objects (DLLs, shared objects)
solution_sequences.pl
call_nth/2	True when Goal succeeded for the Nth time.
distinct/1	True if Goal is true and no previous solution of Goal bound Witness to the same value.
distinct/2	True if Goal is true and no previous solution of Goal bound Witness to the same value.
group_by/4	Group bindings of Template that have the same value for By.
limit/2	Limit the number of solutions.
offset/2	Ignore the first Count solutions.
order_by/2	Order solutions according to Spec.
reduced/1	Similar to distinct/1, but does not guarantee unique results in return for using a limited amount of memory.
reduced/3	Similar to distinct/1, but does not guarantee unique results in return for using a limited amount of memory.
sort.pl
statistics.pl  -- Get information about resource usage
streams.pl  -- Manage Prolog streams
strings.pl
dedent_lines/3	Remove shared indentation for all lines in a string.
indent_lines/3	Add Prefix to the beginning of lines in In.
indent_lines/4	Similar to indent_lines/3, but only adds Prefix to lines for which call(Filter, Line) succeeds.
interpolate_string/4	Establish a string from a template by replacing patterns.
string/4	Implements the quasi quotation syntax string.
string_lines/2	True when String represents Lines.
system.pl
lock_predicate/1	Transform a predicate into a system predicate.
system_mode/1	Switch the system into system or user mode.
system_module/0	Any predicate defined after this declaraction uptil the end of the file will become a system predicate.
unlock_predicate/1	Transform a system predicate into a normal system predicate.
tables.pl  -- XSB interface to tables
terms.pl  -- Term manipulation
thread.pl
call_in_thread/2	Run Goal as an interrupt in the context of Thread.
concurrent/3	Run Goals in parallel using N threads.
concurrent_and/2	Concurrent version of (Generator,Test).
concurrent_and/3	Concurrent version of (Generator,Test).
concurrent_forall/2	True when Action is true for all solutions of Generate.
concurrent_forall/3	True when Action is true for all solutions of Generate.
concurrent_maplist/2	Concurrent version of maplist/2.
concurrent_maplist/3	Concurrent version of maplist/2.
concurrent_maplist/4	Concurrent version of maplist/2.
first_solution/3	Try alternative solvers concurrently, returning the first answer.
thread_pool.pl  -- Resource bounded thread management
threadutil.pl  -- Interactive thread utilities
attach_console/0	Create a new console and make the standard Prolog streams point to it.
attach_console/1	Create a new console and make the standard Prolog streams point to it.
join_threads/0	Join all terminated threads.
tbacktrace/1	Print a backtrace for Thread to the stream user_error of the calling thread.
tbacktrace/2	Print a backtrace for Thread to the stream user_error of the calling thread.
tdebug/0	Enable debug-mode, trapping the graphical debugger on reaching spy-points or errors.
tdebug/1	Enable debug-mode, trapping the graphical debugger on reaching spy-points or errors.
thread_has_console/0	True when the calling thread has an attached console.
threads/0	List currently known threads with their status.
tnodebug/0	Disable debug-mode in all threads or the specified Thread.
tnodebug/1	Disable debug-mode in all threads or the specified Thread.
tprofile/1	Profile the operation of Thread until the user hits a key.
tspy/1	Trap the graphical debugger on reaching Spec in the specified or any thread.
tspy/2	Trap the graphical debugger on reaching Spec in the specified or any thread.
with_stopped_threads/2	Stop all threads except the caller while running once(Goal).
tty.pl
menu/3	Show a menu.
tty_clear/0	Clear the display.
tty_flash/0	Give visual signal if possible, otherwise beep.
ugraphs.pl  -- Graph manipulation library
url.pl  -- Analysing and constructing URL
utf8.pl  -- UTF-8 encoding/decoding on lists of character codes.
varnumbers.pl
max_var_number/3	True when Max is the max of Start and the highest numbered $VAR(N) term.
numbervars/1	Number variables in Term using $VAR(N).
varnumbers/2	Inverse of numbervars/1.
varnumbers/3	Inverse of numbervars/3.
varnumbers_names/3	If Term is a term with numbered and named variables using the reserved term '$VAR'(X), Copy is a copy of Term where each '$VAR'(X) is consistently replaced by a fresh variable and Bindings is a list X = Var, relating the X terms with the variable it is mapped to.
wfs.pl  -- Well Founded Semantics interface
when.pl  -- Conditional coroutining
writef.pl
swritef/2	Use writef/1 or writef/2 and write the result to a string.
swritef/3	Use writef/1 or writef/2 and write the result to a string.
writef/1	Formatted write to the current_output.
writef/2	Formatted write to the current_output.
www_browser.pl  -- Open a URL in the users browser
yall.pl  -- Lambda expressions
zip.pl  -- Access resource ZIP archives