This section describes how data from JavaScript is translated into
Prolog. The interface is primarily designed for passing JavaScript data
as typically used to a natural Prolog representation. In addition a
number of classes are provided to create Prolog specific data structures
such as strings (as opposed to atoms), variables, compound terms, etc.
- Number
- Translate to a Prolog integer or floating point number.
- BigInt
- Translate to a Prolog integer.
- String
- Translate to a Prolog atom. Use
new Prolog.String(text)
to create a Prolog string. See below.
- Boolean
- Translate to one of the Prolog atoms
true or false.
- undefined
- Translate the Prolog atom
undefined.
- null
- Translate the Prolog atom
null.
- Array
- Translate to a Prolog list.
- Objects holding the key
$:Type - Such objects are converted depending on the value for this key. The
interface defines classes to simplify creating such objects.
- s
- Represent a Prolog string. The key
v holds the text. May be
created using new Prolog.string(text). May be created using new
Prolog.String(text).
- r
- Represent a Prolog rational number. The keys
n and d
represent the numerator and denominator. For example,
to represent 1r3, use {$:"r",
n:1, d:3}. May be created using new
Prolog.Rational(n, d), where n and d can be
JavaScript numbers or big integers.
- t
- Represent a Prolog compound term. The object should hold
exactly one key whose value is an array that holds the argument values.
For example a term
point(1,2) is constructed using
{$:"t", point:[1,2]}. May be created using new
Prolog.Compound(functor, args)
- v
- Represent a variable. If the key
v is present this
identifies the variable. Two variables processed in the same translation
with the same identifier represent the same Prolog variable. If the v
key is omitted the variable will be unique. May be created using new
Prolog.Var(id).
- l
- Represent a Prolog list. As a JavaScript
Array we only need
this typed object to create a partial list. The v
key contains the “normal” elements and the key tail
contains the tail of the list. May be created using new
Prolog.List(array, tail).
- Object of class
Object - Plain JavaScript objects are translated into a Prolog
dict.
Note that JavaScript object keys are always strings and (thus) all dict
keys are atoms. This, {1:"one"} is translated into
_{'1': one}.
- ArrayBuffer
- Instances of
ArrayBuffer are translated into a Prolog
string that consists of characters in the range 0 ... 255.
- Objects of a one class not being
Object - Instances of non-plain JavaScript objects are translated into a Prolog blob.
Such objects are written as
<js_Class(id)>. The
Prolog interface allows for passing the objects back and calling methods
on them. See section
13.3.
