Pretty-printing library by wojpok · Pull Request #256 · fram-lang/dbl

wojpok · 2025-08-17T10:27:40Z

A Pretty-pretting library with shift/reset aligment operators and true horizontal catenation.

Copilot

Pull request overview

This PR introduces a comprehensive pretty-printing library for the Fram language, featuring advanced alignment operators using shift/reset mechanisms and true horizontal concatenation. The library enables flexible document layout with automatic width management, non-local alignments for table formatting, and ANSI terminal styling support.

Key Changes:

Implements a sophisticated pretty-printing algorithm with layout selection based on Pareto optimality
Adds shift/reset alignment operators for automatic column alignment without pre-calculation
Provides true vertical concatenation (>+>) in addition to standard horizontal (<>) and line-break ($$) operators

Reviewed changes

Copilot reviewed 20 out of 20 changed files in this pull request and generated 23 comments.

Show a summary per file

File	Description
lib/Pretty.fram	Main public API exposing document types and combinators
lib/Pretty/Core.fram	Core layout algorithm with Pareto selection and stream-based layout generation
lib/Pretty/Size.fram	Size tracking with shift lists for managing floating alignment points
lib/Pretty/Lines.fram	Line representation and rendering with alignment state management
lib/Pretty/Style.fram	ANSI terminal styling support with color and text decoration options
lib/Stream.fram	Adds `lazyStream` helper for lazy stream construction
pretty/examples/Example1-impPrettyPrinter.fram	IMP language pretty-printer demonstrating library features
pretty/examples/Example2-table.fram	Table formatting example using vertical separators
pretty/tutorial/Tutorial1-basic.fram	Basic text document tutorial
pretty/tutorial/Tutorial2-combine.fram	Horizontal combination operator tutorial
pretty/tutorial/Tutorial3-flush.fram	Line break insertion tutorial
pretty/tutorial/Tutorial4-vcat.fram	Vertical concatenation tutorial
pretty/tutorial/Tutorial5-hang.fram	Hanging indent tutorial
pretty/tutorial/Tutorial6-aligns.fram	Shift operator tutorial
pretty/tutorial/Tutorial7-alignScopes.fram	Reset operator for alignment scopes tutorial
pretty/tutorial/Tutorial8-hcat.fram	True horizontal concatenation tutorial
pretty/tutorial/Tutorial9-vsep.fram	Vertical separator usage tutorial
pretty/tutorial/Tutorial10-style.fram	ANSI styling tutorial
pretty/test/Test1-tablesWithHang.fram	Test for table formatting with hanging indents
pretty/test/Test2-alignmentsUnderCat.fram	Test for alignments under concatenation operators

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Copilot · 2025-12-04T12:35:51Z

lib/Pretty.fram

+pub let ($$) (d1 : Doc) (d2 : Doc) = d1.flush.combine d2
+
+{##
+  Puts 2 documents in paraller. The last line will always be aligned with


Spelling error: "paraller" should be "parallel".

Suggested change

Puts 2 documents in paraller. The last line will always be aligned with

Puts 2 documents in parallel. The last line will always be aligned with

Copilot · 2025-12-04T12:35:51Z

lib/Pretty/Size.fram

+        SShift {width=width + w, dangle=dangle + w} tl 
+    end in
+
+  # Handles paraller join of two given shift list


Spelling error: "paraller" should be "parallel".

Suggested change

# Handles paraller join of two given shift list

# Handles parallel join of two given shift list

Copilot · 2025-12-04T12:35:51Z

lib/Pretty/Size.fram

+    end in
+
+  # Handles paraller join of two given shift list
+  # By assumpion w1 does NOT contain SLast label


Spelling error: "By assumpion" should be "By assumption".

Suggested change

# By assumpion w1 does NOT contain SLast label

# By assumption w1 does NOT contain SLast label

Copilot · 2025-12-04T12:35:52Z

lib/Pretty/Size.fram

+    assertEqF (t <> t.shift).width
+      (SShift {width=3, dangle=3} (SLast {width=3} (SFix {width=3}))));
+
+  testCase "`shift` aligns paraller structures" (fn () =>


Spelling error: "paraller" should be "parallel".

Suggested change

testCase "`shift` aligns paraller structures" (fn () =>

testCase "`shift` aligns parallel structures" (fn () =>

Copilot · 2025-12-04T12:35:52Z

lib/Pretty/Size.fram

+  are willing to globally align with others. 
+
+  The `SLast' node is a label that indicates a line where <> will attach
+  foramatted text. In every Size object there is exactly one SLast node.


Spelling error: "foramatted" should be "formatted".

Suggested change

foramatted text. In every Size object there is exactly one SLast node.

formatted text. In every Size object there is exactly one SLast node.

Copilot · 2025-12-04T12:35:57Z

lib/Pretty.fram

+{## ## The pretty-printer module. ##}
+
+{##
+  This module containes fully-featured pretty-printer library.


Spelling error: "containes" should be "contains".

Suggested change

This module containes fully-featured pretty-printer library.

This module contains fully-featured pretty-printer library.

Copilot · 2025-12-04T12:35:57Z

lib/Pretty.fram

+pub let (text : String -> Doc) = Core.text
+
+{##
+  Empty documnt.


Spelling error: "documnt" should be "document".

Suggested change

Empty documnt.

Empty document.

Copilot · 2025-12-04T12:35:57Z

lib/Pretty.fram

+{## Enclosing of a document. ##}
+pub let enclose l r d = l <> r <> d
+
+{## Equotes given docuemnt. ##}


Spelling error: "docuemnt" should be "document".

Suggested change

{## Equotes given docuemnt. ##}

{## Equotes given document. ##}

Copilot · 2025-12-04T12:35:58Z

lib/Pretty/Size.fram

+  # The starting point of algorithm
+  # The <> catenation happens at `SLast' node of w1, thus
+  # width is copied up until `SLast' and then combineWs
+  # operation is permormed. The SLast label will be


Spelling error: "permormed" should be "performed".

Suggested change

# operation is permormed. The SLast label will be

# operation is performed. The SLast label will be

Copilot · 2025-12-04T12:35:58Z

lib/Pretty/Lines.fram

+    (x, p + static)
+  else
+    match List.drop (n - 1) sh with
+    | [] => runtimeError "Alignment - not enought shifts"


Spelling error: "enought" should be "enough".

Suggested change

| [] => runtimeError "Alignment - not enought shifts"

| [] => runtimeError "Alignment - not enough shifts"

wojpok · 2025-12-11T09:12:50Z

I moved this PR as draft. I will update it once testing framework is ready

fresh pretty printer barnch

4d899c4

wojpok force-pushed the pp branch from 5d1904e to 79ff8a9 Compare October 23, 2025 09:08

Pretty-printer

8027ea4

wojpok force-pushed the pp branch from 79ff8a9 to 8027ea4 Compare October 23, 2025 09:10

Foxinio mentioned this pull request Oct 23, 2025

Test Module #259

Closed

wojpok added 2 commits October 27, 2025 11:45

full code, stress tests

f961d2a

structurized demo, explicit color enumeration in interface file

14a212b

This was referenced Nov 3, 2025

First-class lazy evaluation #264

Merged

Extended List module #265

Merged

Streams #266

Merged

Basic ANSI modes #267

Merged

Prelude extension #268

Merged

wojpok added 2 commits November 23, 2025 20:52

updated stdlib libraries

1d54572

fix pipeline

995a4ff

zielinsky requested a review from Copilot December 4, 2025 12:28

Copilot started reviewing on behalf of zielinsky December 4, 2025 12:29 View session

Copilot finished reviewing on behalf of zielinsky December 4, 2025 12:32

Copilot AI reviewed Dec 4, 2025

View reviewed changes

wojpok marked this pull request as draft December 11, 2025 09:12

wojpok added 4 commits January 21, 2026 19:28

Merge branch 'master' into pp

79738e4

tests reworked

259d5a8

horizontal fill using shifts

73d6ed2

code formatted

3e2d903

wojpok marked this pull request as ready for review January 21, 2026 19:27

wojpok added 5 commits January 22, 2026 12:07

interface improvements

bfeb5bc

minor improvements to generator algorithm

285eb28

Merge branch 'master' into pp

9de033b

faster size comparison

0f47f73

bugfixed style calculation

83f245f

fix tests, move examples to dedicated example folder

00df713

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Pretty-printing library#256

Pretty-printing library#256
wojpok wants to merge 16 commits intofram-lang:masterfrom
wojpok:pp

wojpok commented Aug 17, 2025 •

edited

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	Puts 2 documents in paraller. The last line will always be aligned with
	Puts 2 documents in parallel. The last line will always be aligned with

	# Handles paraller join of two given shift list
	# Handles parallel join of two given shift list

	# By assumpion w1 does NOT contain SLast label
	# By assumption w1 does NOT contain SLast label

	testCase "`shift` aligns paraller structures" (fn () =>
	testCase "`shift` aligns parallel structures" (fn () =>

	foramatted text. In every Size object there is exactly one SLast node.
	formatted text. In every Size object there is exactly one SLast node.

	This module containes fully-featured pretty-printer library.
	This module contains fully-featured pretty-printer library.

	{## Equotes given docuemnt. ##}
	{## Equotes given document. ##}

	# operation is permormed. The SLast label will be
	# operation is performed. The SLast label will be

	\| [] => runtimeError "Alignment - not enought shifts"
	\| [] => runtimeError "Alignment - not enough shifts"

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wojpok commented Aug 17, 2025 •

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