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document Rust-based builtins in lib/builtins.rs (#2030) #2265

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document Rust-based builtins in lib/builtins.rs (#2030) #2265

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133 changes: 132 additions & 1 deletion src/lib/builtins.pl
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,137 @@
internal settings and basic I/O are all here.
*/

%% @>(?X, ?Y)
%
% Compares X and Y in the term order mandated by the ISO standard (section 7.2).
% Terms of different types are sorted in the ascending ordering:
%
% 1. Variable
% 2. Floating point
% 3. Integer
% 4. Atom
% 5. Compound
%
% If X and Y are both within one of the five categories, they are ordered as follows.
%
% 1. Variables: implementation-dependent, Scryer compares variables according to their
% locations in its global and local heap. The address space of the local heap is
% always above that of the global heap in the WAM architecture used by Scryer.
% 2. Floating point and 3. Integer: Ordered by numeric value.
% 4. X precedes Y if X is the null atom ('') and Y is not, or if X lexicographically
% precedes Y.
% 5. X precedes Y if the arity of X is less than that of Y; if the arities are equal,
% X precedes Y if its atom precedes Y's atom according to 4. If the functor names
% and arities are equal, the subterms of X and Y are compared recursively from left
% to right.

%% @<(?X,Y)
%% @>=(?X,?Y)
%% @=<(?X,?Y)
%
% These operators implement term comparisons according to the term
% order described in the entry for (@>)/2.

%% ==(?X,?Y)
%
% True iff X and Y are identical terms. Term identity is defined according to the
% ordering described in the entry for (@>)/2.

%% \==(?X,?Y)
%
% True iff X and Y are not identical, the negation of (==)/2.

%% >(+X,+Y)
%% <(+X,+Y)
%% >=(+X,+Y)
%% =<(+X,+Y)
%% =:=(+X,+Y)
%% =\=(+X,+Y)
%
% Numeric comparison operators respectively true if X is greater, less
% than, greater than or equal, less than or equal, equal or not equal
% to Y. X and Y must be instantiated to numbers.
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Small correction: "X and Y can be any ground arithmetical expression" or another wording "must be evaluable to numbers"


%% is(?X, +Y)
%
% Evaluate the evaluable functor of Y representing an arithmetic
% expression to a numeric result and bound it to ?X. Arithmetic expressions
% are constructed from a set of operators with pre-defined arities and precedences
% documented in section 9 of the ISO standard.

%% acyclic_term(?X)
%
% True iff ?X contains no variables bound to it.

%% arg(N, Term, Arg)
%
% True iff the Nth argument of Term is Arg.

%% compare(?Atom, +X, +Y)
%
% Compares X and Y according to the standard term order and unifies
% ?Atom to either <, >, or = according to whether X is less than,
% greater than or equal to Y.

%% copy_term(?X, ?Y)
%
% Produce a deep copy of ?X and unify it to ?Y.

%% functor(Term, Name, Arity)
%
% - True iff Term is a compound term whose Identifier is Name and arity Arity, or
% - Term is an atomic term equal to Name and Arity is 0.

%% ground(Term)
%
% True iff Term contains no free variables as subterms.

%% keysort(List, Sorted)
%
% True iff List is a list of elements with the format Key-Value and
% Sorted is a list containing the elements of List sorted according to
% the value of Key in ascending order following standard order. The
% relative order of elements of List with the same key shall not
% change in the Sorted list.

%% sort(List, Sorted)
%
% True iff Sorted is a list containing the non-duplicated elements of
% List sorted in ascending order following standard order.

%% atom(?X)
%
% True iff X is bound to an atom.

%% compound(?X)
%
% True iff X is bound to a compound term.

%% integer(?X)
%
% True iff X is bound to an integer.

%% number(?X)
%
% True iff X is bound to an number (an integer, rational number or floating point).

%% rational(?X)
%
% True iff X is bound to a rational number.

%% float(?X)
%
% True iff X is bound to a floating point number.

%% nonvar(?X)
%
% True iff X is not a free variable.

%% var(?X)
%
% True iff X is a free variable.

% % (7.2)

% unify.

Expand Down Expand Up @@ -1828,7 +1959,7 @@
%% subsumes_term(General, Specific)
%
% True iff General can be made equivalent to Specific by only binding variables
% in Generic. The implementation unifies with occurs check always and ensures that
% in General. The implementation unifies with occurs check always and ensures that
% the variables of Specific did not change. Some examples:
%
% ```
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