Changelog for pandoc-filter-indent

0.3.3.0 Nov 17 2025

Unicode and Operator Support

• Add comprehensive support for GHC UnicodeSyntax extension operators
  • Unicode lambda (λ) now correctly renders as \lambda
  • All GHC UnicodeSyntax operators now supported: ∷, ⇒, →, ←, ⤚, ⤙, ⤜, ⤛, ★, ∀, ⦇, ⦈, ⟦, ⟧, ⊸
  • ASCII and Unicode versions of operators produce identical LaTeX output
• Fix unicode lambda (λ) character handling in both Haskell and Skylighting tokenizers
  • Add splitUnicodeLambda to handle tokens like "λx" → ["λ", "x"]
• Fix lambda expressions rendering in LaTeX math mode
• Fix backslash operators (, \, /, /, etc.) rendering
• Add preprocessing for Skylighting tokenizer to handle split backslash operators
• Add fixBracketOperators to merge GHC bracket operators: (|, |), [|, |]

• < as Cartesian product (\times)

• :-> as \longmapsto
• Design choice: * renders as \times (multiplication) since modern Haskell uses Type for kinds
  • Unicode ★ renders as \star for legacy kind annotations
  • Tokenizers cannot distinguish between kind and multiplication contexts
  • TODO: Make this configurable for projects with legacy kind syntax

Tokenizer Differences and Solutions

• Root cause identified: Haskell and Skylighting tokenizers produce different token types
  • Haskell tokenizer: most operators → TOther
  • Skylighting tokenizer: some operators → TOperator (e.g., *, >-, -<, >>-, -<<)
  • Unicode ∀: TKeyword (Haskell) vs TOther (Skylighting)
  • Unicode λ: TVar (Haskell) vs TOther (Skylighting)
• Solution: Introduced OpOrOther pattern synonym using PatternSynonyms extension
  • Eliminates code duplication when handling same operator from both tokenizers
  • Cleaner syntax: formatToken (OpOrOther "->") = mathop "to"

Bug Fixes

• Fix extraColumns and tableColumns deduplication mismatch
  • Both now use text column position deduplication to avoid gaps in table column indices
  • Fixes prop_tableColumns test failure on inputs like "\n a"
• Rename subscripts to subAndSuperscripts with proper superscript support

Testing

• Add comprehensive test suite for lambda expressions and backslash operators
• Add unit tests for all GHC UnicodeSyntax operators (UnicodeOperatorSpec)
  • Tests verify ASCII and Unicode versions produce identical LaTeX output
  • Tests now fail on error instead of just warning (enforced with error function)
• Add tokenizer comparison tests (TokenizerTest)
• Refactor test suite: extract common test pattern into helper function
• Improve test readability: reduce code duplication in property tests

Code Quality

• Code cleanup: remove unused LANGUAGE pragmas, add missing pragmas
• Code cleanup: use newtype for single-field records, use concatMap and elemIndex
• Code cleanup: remove redundant $ operators and brackets
• Code cleanup: fix pattern matching style (otherwise -> _)
• Code cleanup: use hPrint instead of hPutStrLn . show

Documentation

• Add UNICODE_OPERATORS.md explaining Unicode operator support, design decisions, and limitations
• Document tokenizer differences and solutions
• Document the * vs ★ rendering choice with rationale

Release history

0.3.2.0 Sep 29 2021

• stacked subscripts
• lambda in Haskell tokenizer
• greek letters for special variable names: eps, pi, rho
• automatically append required LaTeX packages (broken for Beamer output)
• Mapsto for |=>

0.3.1.0 Jan 15 2021

• Slightly improved formatting with SkyLighting and LaTeX

0.3.0.0 Jan 15 2021

• Support default syntaxes from skylighting.

0.2.3.0 Jan 12 2021

• fixed minor issue that disabled inline rendering.

0.2.2.0 Jan 12 2021

• Fixed problem with declaring too few columns in LaTeX
• Inline code formatting
• Removed indent marks from parenthesised operators: "(+)"
• Removed indent marks from functions promoted to operators like "mappend"
• Fixed rendering of indent mark at the start of the column

0.1.0.0 Dec 1 2020

• Initial release supporting LaTeX and HTML output

0.2.0.0 Dec 2 2020

• Preliminary support for Tikzmarks
• Updated README

0.2.1.0 Dec 2 2020

• Extended code documentation
• Cleanups