. Common Prolog Predicates
(semicolon):
; ::infix= ; ::=`(1st) or (2nd)`.
(comma):
, ::infix= ; ::=`(1st) and (2nd)`.
:- ::infix=`(1st) if (2nd)`.
-> ::infix=` If (1st) then (2nd)`.
< ::infix=` Less Than - numerical comparison. Evalutaes both sides.`.
<= ::infix=` Less Than or Equal - numerical comparison. Evalutaes both sides.`.
= ::infix=` True if both terms are the same, or makes them match.`.
== ::infix=` True if two terms X and Y are identical. Does not force unification.`.
\== ::infix= ` test for inequality of structures. No unification`.
=:= ::infix=` Equal to - numerical comparison. Evaluates both sides. `.
=\= ::infix=` Unequal to - numerical comparison. Evaluates both sides. `.
> ::infix=` Greater Than - numerical comparison. Evaluates both sides.`.
>= ::infix=` Greater than of equal - numerical comparison. Evaluates both sides.`.
is ::infix=` Expression is evaluated and X becomes the value.`.
abolish ::=` remove all clause/definitions of (_) from the data base`.
abort ::=` Probably terminates current query, or clause, or ... .`.
ancestors  ::=` (_) instantiated to list of goals called up to this point.`.
arg ::=` (3rd) either becomes or is the (1st)th argument in structure (2nd).`.
ascii ::=` (1st) is/becomes an atomic character with ascii code (2nd)`.
assert ::=` Adds clause (_) somewhere in knowledge base.`.
asserta ::=` Clause(_) is placed at the beginning of the database.`.
assertz ::=` Clause(_) is placed at the end of the database.`.
atom ::=` True if (_) is a non-numeric atom.`.
atomic ::=` True if (_) is an atom or a number.`.
body ::=` (2nd) is set to the body of (1st) ((1st)=Head:-(2nd))`.
char(n, a, Z) ::=` Z set to the nth character in atom a.`.
close(FileName) ::=` close file, NOT standard input or output.`.
conc(Var, term) ::=` Var is/becomes list [term].`.
concat(List, Var) ::=` Var is/becomes atom made up of elements of List.`.
consult('filename') ::=` appends correct terms from file`.
consult(['filemane',...]) ::=` consults listed files.`.
define(Atom(Args)) ::=` experimental make unique definition of Atom`.
define(Atom, Body) ::=` experimental make unique definition of Atom.`.
definition(X,Y) ::=` Y becomes a clause in definition of atom X.`.
defop(Precedence, Type, Name) ::=` Define Name to be an operator, see documents.`.
dump ::=`?? builtin( notOp, 0, 0, "dump", dump).`.
ed functor ::=` Starts up your $EDITOR on the terms defining functor.`.
ef file ::=` Lets you edit a file.`.
eof ::=`??  builtin( notOp, 0, 0, "eof", p_eof). ??`.
file(FileName,ListOfAtoms)::=`After consultation ListOfAtoms shows the predicates defined in FileName`.
first_clause(Head, Body) ::=` Find first clause that fits Head, Body`.
free(X) ::=`??  builtin( notOp, 0, 1, "free", p_free). ??`.
free_proc(X) ::=`??  builtin( notOp, 0, 1, "free_proc", p_free_proc). ??`.
functor(T, Functor, Arity) ::=` T becomes Functor of Arity Arguments`.
functor(Term,F,A) ::=` F  becomes name and A the arity of Term.`.
getc(C) ::=` C is or becomes the next character on the input.`.
get0(ASCII):-getc(Char), ascii(Char,ASCII).  % gets ASCII code of next char
goal(X,Y,Z) ::=`??  builtin( notOp, 0, 3, "goal", goal). ??`.
halt ::=` end of session, terminates Prolog.`.
head(Clause, Head) ::=` sets Head to be the head of the clasue Clause.`.
help:- print('To exit input: halt!, To read the manual: man!'),... .
integer(X) ::=` true if X is instantiated to an integer.`.
length(List,L) ::=` L instantiated to number elements in List.`.
listing ::=` outputs all user defined clauses on current output.`.
man:-system('man prolog').
match_args(F,I,L) ::=` partial match of Ith,I+1th, args with elelements of L.`.
member(Item, List) ::=` True if Member in List else generates Members in List.`.
next_clause(X, Y) ::=` X must be a Clause in the data base, Y is set to the next.`.
nl ::=` Outputs a new line character.`.
nonvar(X) ::=` tests if X is currently instantiated to a non-variable term.`.
not P ::=` Success if P fails , Variables in P can be uninstantiated.`.
nth(X, N, L) ::=` true if Nth element of list L is X, Can set X, N, or L.`.
numbervars(X,Y,Z) ::=`??  builtin( notOp, 0, 3, "numbervars", number_vars). ??`.
nvars(X,Y) ::=`??  builtin( notOp, 0, 2, "nvars", nvars). ??`.
offset(X,Y) ::=`??  builtin( notOp, 0, 2, "offset", offset). ??`.
op(Precedence, Type, [Name, ..Rest]) ::=` declares list of operators.`.
pp X ::=` Print out pretty version of definitions of atom X.`.
prin(Term,...) ::=` Output Terms (no spaces between, no nl).`.
print(Term,...) ::=` Output Term with nl.`.
prompt(Old, new) ::=` Sets the 'read' prompt to 'new', Old set to previous value..`.
putc(C) ::=` Outputs ASCII character for C permanently.`.
quoted(X) ::=`??  builtin( notOp, 0, 1, "quoted", quoted). ??`.
ratom(X) ::=` Read atom into X, test if next input atom is X.`.
read(Term) ::=` Inputs complete, correct and terminated Term.`.
read_from_this_file ::=`??  builtin( notOp, 0, 0, "read_from_this_file", read_in). ??`.
redefine(atom(Value),newatom(NewValue)) ::=` replaces first definition of atom.`.
redefine(Head,Body,NewHead,NewBody) ::=` replaces definition.`.
remob(X) ::=`??  builtin( notOp, 0, 1, "remob", remob). Remove Object? ??`.
rename(X,Y) ::=`??  builtin( notOp, 0, 2, "rename", rename). ??`.
retract(Clause) ::=` remove first matching clause and unify variables.`.
retract(Head) ::=` warning and then remove first unifiable clause.`.
retract(Head, Body) ::=` remove first matching clause and unify variables.`.
retract_head(Head)::=` remove first matching clause and unify variables.`.
save FileName ::=` Saves data base in file FileName (normally in quotes).`.
see(File) ::=` current input becomes File, and if necesary opens it.`.
seeing(F) ::=` F becomes/is the current file.`.
seen ::=` close current input file.`.
sh ::=` escape temporarily to UNIX by spawning  an interactive subshell.`.
show X ::=` let user see documentatation.`.
skip(C) ::=` Inputs data to match C or matches C to next input`.
spy predicate ::=` Start to trace the predicate.`.
statistics ::=` outputs current figures on bindings etc.`.
system(Command) ::=` Obeys UNIX command, system('cat help').`.
tab(N)  ::=` Outputs N blanks (permanently).`.
tell(File) ::=` The current output becomes File (append mode).`.
telling(F) ::=` F is or becomes the name of the current output file.`.
term(X,Y,Z) ::=`??  builtin( notOp, 0, 3, "term", pterm). ??`.
time ::=` turns on some kind of timing mechanism.`.
told ::=` close output file.`.
trace [Predicate,Predicate, ..Rest] ::=` turn on tracing of a list of predicates.`.
univ(F,L) ::=` Makes functor F match elements of list L. F and/or L can be set.`.
unlink_clause(X) ::=` Given X is instantiated to a clause then clause is removed.`.
unspy predicate ::=` Stop tracing the predicate.`.
untrace [Predicate,Predicate, ..Rest] ::=` turn off tracing of a list.`.
var(X) ::=` true if X is an uninstantiated variable or unified with a variable.`.
write(Term) ::=` outputs Term with no period or quotes etc.`.