Did you know ... | Search Documentation: |
Pack logtalk -- logtalk-3.85.0/manuals/_sources/libraries/nested_dictionaries.rst.txt |
.. _library_nested_dictionaries:
nested_dictionaries
This library provides nested dictionary implementations based on private
extensions to the dictionaries
library objects. The representations
of a nested dictionary should be regarded as opaque terms and only
accessed using the library predicates.
This library is experimental, a work in progress, and future versions can introduce incompatible changes.
Open the `../../docs/library_index.html#nested-dictionaries <../../docs/library_index.html#nested-dictionaries>`__ link in a web browser.
To load all entities in this library, load the loader.lgt
file:
::
| ?- logtalk_load(nested_dictionaries(loader))
.
To test this library predicates, load the tester.lgt
file:
::
| ?- logtalk_load(nested_dictionaries(tester))
.
First, select the nested dictionary implementation that you want to use.
For cases where the number of elements is relatively small and
performance is not critical, nbintree
can be a good choice. For
other cases, navltree
or nrbtree
are likely better choices. If
you want to compare the performance of the implementations, either
define an object alias or use a uses/2 directive so that you can
switch between implementations by simply changing the alias definition
or the first argument of the directive. Note that you can switch between
implementations at runtime without code changes by using a parameter
variable in the first argument of a uses/2 directive.
To create an empty nested dictionary, you can use the new/1 predicate. For example:
::
| ?- navltree::new(Dictionary)
.
Dictionary = ...
yes
You can also create a new nested dictionary from a curly bracketed term representation (see below) by using the predicate as_nested_dictionary/2. For example:
::
| ?- navltree::as_nested_dictionary(
{a-1, b-{c-3, d-{e-7,f-8}}},
Dictionary
)
.
Dictionary = ... yes
Several predicates are provided to insert, lookup, update, and delete key-value pairs given a list of keys interpreted as an access path to a nested dictionary. For example:
::
| ?- navltree::as_nested_dictionary(
{a-1, b-{c-3, d-{e-7,f-8}}},
Dictionary
)
,
navltree::lookup_in([b,d,f], Value, Dictionary)
.
Dictionary = ... Value = 8 yes
For details on these and other provided predicates, consult the library API documentation.
To simplify importing and exporting data into a nested dictionary, the library provides as_nested_dictionary/2 and as_curly_bracketed/2 predicates that work with a curly term representation. This format is based on the JSON data interchange format.
A dictionary is represented by the {Pairs}
term where Pairs is a
conjunction of Key-Value
or Key:Value
pairs and Value
can be
a nested dictionary or lists of pairs. An empty dictionary is
represented using the {}
term.