dependent-literals-plugin: Dependent integer literals

This plugin implements pseudo-dependently-typed integer literals.

This means the value of an integer literal is available at the type level, and can be used for things like validation or type inference. For example, the SInt instance refines unknown type-level Nat variables to the particular literal value, and the Fin instance emits compile-time errors for out-of-range values. So, given mkVec :: SInt n -> (Fin n -> a) -> Vec n a, mkVec 4 will have type (Fin 4 -> a) -> Vec 4 a, and trying to type-check 4 :: Fin 4 will report a type error saying that 4 is out of range.

Patterns get a similar treatment, too, so case (x :: SInt n) of { 1 -> Just Refl; _ -> Nothing } :: Maybe (n :~: 1) can type-check: the act of matching against 1 proved that the type-level n was equal to 1, so Refl can type-check as n :~: 1.

To use this, enable the extensions DataKinds, FlexibleContexts, ViewPatterns, and TypeApplications, add dependent-literals and dependent-literals-plugin to your package's dependencies, and add -fplugin=DependentLiterals.Plugin to ghc-options to enable the plugin globally, or use OPTIONS_GHC pragmas to enable the plugin on a per-module basis. "Normal" integral types should still behave as normal, but literals and numeric patterns will become supported for SInt and Fin, and will provide additional information to the type checker automatically.

Modules

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Flags

Manual Flags

Name	Description	Default
error_message_tests	Enable tests that emit error messages for inspection.	Disabled

Use -f <flag> to enable a flag, or -f -<flag> to disable that flag. More info

Downloads

• dependent-literals-plugin-0.1.0.2.tar.gz [browse] (Cabal source package)
• Package description (revised from the package)

Note: This package has metadata revisions in the cabal description newer than included in the tarball. To unpack the package including the revisions, use 'cabal get'.

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Package maintainers

• AndrewPritchard

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