basilisp.pprint namespace (#1258)

Fixes #513

Author: chrisrink10

CHANGELOG.md

@@ -13,18 +13,20 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
  * Added support for f-strings (#922)
  * Added the `aslice` macro to facilitate the use of Python style `array[start:stop:step]` slicing in Basilisp (#1248)
  * Added the `IPending` interface which is implemented by delays, futures, and promises (#1260)
+ * Added the `basilisp.pprint` namespace (#513)
 
 ### Changed
- * Removed implicit support for single-use iterables in sequences, and introduced `iterator-seq` to expliciltly handle them (#1192)
+ * Removed implicit support for single-use iterables in sequences, and introduced `iterator-seq` to explicitly handle them (#1192)
  * `basilisp.core/str` now delegates to the builtin Python `str` in all cases except for customizing the string output for builtin Python types (#1237)
  * Optimised mainstream seq-consuming functions by coercing their inputs into `seq` upfront (#1234)
  * Renamed `awith` and `afor` to `with-async` and `for-async` for improved clarity (#1248)
  * `basilisp.main.init` will only initialize the runtime environment on the first invocation (#1242)
  * Updated support for PyPy to 3.9 and 3.10 (#1265)
 
 ### Fixed
- * Fix a bug where protocols with methods with leading hyphens in the could not be defined (#1230)
+ * Fix a bug where protocols with methods with leading hyphens in method names could not be defined (#1230)
  * Fix a bug where attempting to `:refer` a non-existent Var from another namespace would throw an unhelpful exception (#1231)
+ * Fixed a bug where `(range 0)` would return `(0)` rather than than `()` as expected (#1258)
 
 ## [v0.3.8]
 ### Added

docs/api/pprint.rst

@@ -1,10 +1,119 @@
 basilisp.pprint
 ===============
 
+.. lpy:currentns:: basilisp.pprint
+
 .. toctree::
    :maxdepth: 2
    :caption: Contents:
 
+.. _pretty_printing:
+
+Pretty Printing
+---------------
+
+Pretty printing built-in data structures is as easy as a call to :lpy:fn:`pprint`.
+
+.. code-block::
+
+ (require '[basilisp.pprint :as pprint])
+ (pprint/pprint (range 30))
+
+The output can be configured using a number of different control variables, which are expressed as dynamic Vars.
+
+- :lpy:var:`*print-base*`
+- :lpy:var:`*print-miser-width*`
+- :lpy:var:`*print-pretty*`
+- :lpy:var:`*print-pprint-dispatch*`
+- :lpy:var:`*print-radix*`
+- :lpy:var:`*print-right-margin*`
+- :lpy:var:`*print-sort-keys*`
+- :lpy:var:`*print-suppress-namespaces*`
+
+You can pretty print the last result from the REPL using the :lpy:fn:`pp` convenience macro.
+
+As an alternative, the :lpy:fn:`write` API enables a more ergonomic API for configuring the printer using keyword arguments rather than dynamic Vars.
+
+.. code-block::
+
+ (pprint/write (ns-interns 'basilisp.pprint) :sort-keys true)
+ ;; {*current-length* #'basilisp.pprint/*current-length*
+ ;;  ...
+ ;;  write-out #'basilisp.pprint/write-out}
+
+.. _custom_pretty_print_dispatch_function:
+
+Custom Pretty Print Dispatch Function
+-------------------------------------
+
+The default dispatch function is :lpy:fn:`simple-dispatch` which can print most builtin Basilisp types.
+Using the builtin macros and utilities, it is possible to create a custom dispatch function.
+
+.. _pretty_printing_concepts:
+
+Pretty Printing Concepts
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+The pretty printing algorithm used in ``basilisp.pprint`` is based on the XP algorithm defined in Richard Water's 1989 paper "XP: A Common Lisp Pretty Printing System" as adapted in Clojure's ``pprint`` by Tom Faulhaber.
+There are three basic concepts in the XP algorithm which are necessary in order to create a custom dispatch function.
+
+- *Logical blocks* are groups of output that should be treated as a single unit by the pretty printer.
+  Logical blocks can nest, so one logical block may contain 0 or more other logical blocks.
+  For example, a vector may contain a map; the vector would be a logical block and the map would also be a logical block.
+  ``simple-dispatch`` even treats key/value pairs in associative type outputs as a logical block, so they are printed on the same line whenever possible.
+
+  A dispatch function can emit a logical block using the :lpy:fn:`pprint-logical-block` macro.
+
+- *Conditional newlines* can be emitted anywhere a newline may need inserted into the output stream.
+  Newlines can be one of 3 different types which hints to the pretty printer when a newline should be emitted.
+
+  Dispatch functions can emit newlines in any supported style using the :lpy:fn:`pprint-newline` function.
+
+  - ``:linear`` style newlines should be emitted whenever the enclosing logical block does not fit on a single line.
+    Note that if any linear newline is emitted in a block, every linear newline will be emitted in that block.
+
+  - ``:mandatory`` style newlines are emitted in all cases.
+
+  - ``:miser`` style newlines are emitted only when the output will occur in the "miser" region as defined by :lpy:var:`*print-miser-width*`.
+    This allows additional newlines to be emitted as the output nests closer to the right margin.
+
+- *Indentation* commands indicate how indentation of subsequent lines in a logical block should be defined.
+  Indentation may be defined relative to either the starting column of the current logical block or to the current column of the output.
+
+  Dispatch functions can control indentation using the :lpy:fn:`pprint-indent` function.
+
+Pretty printing is most useful for viewing large, nested structures in a more human-friendly way.
+To that end, dispatch functions wishing to print any collection may want to use the :lpy:fn:`print-length-loop` macro to loop over the output, respecting the :lpy:var:`basilisp.core/*print-length*` setting.
+
+Dispatch functions which may need to be called on nested elements should use :lpy:fn:`write-out` to ensure that :lpy:var:`basilisp.core/*print-level*` is respected.
+Scalar values can be printed with :lpy:fn:`basilisp.core/pr` or just written directly to :lpy:var:`*out*`.
+
+.. _unimplemented_pprint_features:
+
+Unimplemented Features
+----------------------
+
+The following features from ``clojure.pprint`` are not currently implemented:
+
+- ``:fill`` newlines
+- ``code-dispatch`` for printing code
+- ``cl-format``
+
+.. _pprint_references:
+
+References
+----------
+
+- Tom Faulhaber et al.; ``clojure.pprint`` (`API <https://clojure.github.io/clojure/clojure.pprint-api.html>`_, `Documentation <https://clojure.github.io/clojure/doc/clojure/pprint/PrettyPrinting.html>`_)
+- Oppen, Derek; \"Prettyprinting\"; October 1980
+- Waters, Richard; \"XP: A Common Lisp Pretty Printing System\"; March 1989
+
+.. _pprint_api:
+
+API
+---
+
 .. autonamespace:: basilisp.pprint
    :members:
-   :undoc-members:
+   :undoc-members:
+   :exclude-members: LogicalBlock, StartBlock, EndBlock, Blob, Newline, Indent, *current-length*, *current-level*

docs/differencesfromclojure.rst

@@ -225,6 +225,7 @@ Basilisp includes ports of some of the standard libraries from Clojure which sho
 * :lpy:ns:`basilisp.data` is a port of ``clojure.data``
 * :lpy:ns:`basilisp.edn` is a port of ``clojure.edn``
 * :lpy:ns:`basilisp.io` is a port of ``clojure.java.io``
+* :lpy:ns:`basilisp.pprint` is a port of ``clojure.pprint`` (excluding support for ``cl-format``)
 * :lpy:ns:`basilisp.set` is a port of ``clojure.set``
 * :lpy:ns:`basilisp.shell` is a port of ``clojure.java.shell``
 * :lpy:ns:`basilisp.stacktrace` is a port of ``clojure.stacktrace``

docs/interfaces.rst

@@ -22,7 +22,7 @@ In day-to-day usage, you will not typically need to use these interfaces, but th
    .. automethod:: _lrepr
    .. automethod:: lrepr
 
-.. lpy:currentns::  basilisp.core
+.. lpy:currentns:: basilisp.core
 
 .. automodule:: basilisp.lang.interfaces
    :members:

src/basilisp/core.lpy

@@ -2589,7 +2589,7 @@
   ([]
    (iterate inc 0))
   ([end]
-   (lazy-seq (cons 0 (range 1 end))))
+   (range 0 end))
   ([start end]
    (lazy-seq
     (when (< start end)