An alternative to CPP
summary
Proposal implements a GHC builtin minimal CPP replacement that only supports conditional compilation, integrates into the lexer/parser pipeline, and aims to be tooling friendly and round‑trippable with exact‑print. It parses directives as tokens, evaluates simple operators (and/or/not, <, >), omits include files, and processes only directives in column 1 to avoid label conflicts. Disabled branches become comments so edits preserve layout, turns disabled lines into comments, and a Hackage run shows 508 failures (0.25% of 204k)—targeting ~90% coverage.
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chapters (13)
- 0:00Intro
- 0:24What is CPP
- 1:17CPP in Cabal
- 2:09Why is CPP a problem
- 3:47The problem with CPP
- 4:21The alternative
- 5:28Goals
- 7:08Implementation
- 8:20Compliance
- 9:20Usage
- 12:12Line pragmas
- 13:07Code modification
- 20:49Experience report
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