hoogle

name	hoogle
description	Search Haskell APIs using Hoogle. Use when working with Haskell projects to look up function signatures, find functions by type, discover library documentation, or identify which module exports an item.

Hoogle API Search

Hoogle is a Haskell API search engine. Use it to find functions by name or by type signature.

When To Use Hoogle

Use Hoogle when:

• Working with Haskell code and needing to find a function.
• Looking up a type signature.
• Searching for functions that match a type signature, such as a -> b -> a.
• Finding which module exports a particular function.
• Looking up documentation for Haskell functions.

Search Methods

Search by function name:

.codex/skills/hoogle/scripts/hoogle-search.sh "map"

Search by type signature:

.codex/skills/hoogle/scripts/hoogle-search.sh "a -> b -> a"

Search with a package filter:

.codex/skills/hoogle/scripts/hoogle-search.sh "+base map"
.codex/skills/hoogle/scripts/hoogle-search.sh "+containers Data.Map.lookup"

Get detailed information for the first result:

.codex/skills/hoogle/scripts/hoogle-search.sh "foldl" --info

Remote search is available when local search is unavailable or insufficient:

.codex/skills/hoogle/scripts/hoogle-remote.sh "map"

Result Shape

The search scripts return JSON:

{
  "results": [
    {
      "url": "https://hackage.haskell.org/package/base/docs/Prelude.html#v:map",
      "module": { "name": "Prelude", "url": "..." },
      "package": { "name": "base", "url": "..." },
      "item": "map :: (a -> b) -> [a] -> [b]",
      "docs": "..."
    }
  ],
  "query": "map",
  "count": 10
}

Key fields are item, docs, module.name, and package.name.

Database Initialization

Before local searching, ensure the Hoogle database exists:

.codex/skills/hoogle/scripts/hoogle-init-db.sh

For project-specific searches, generate a local database from Haddock docs:

.codex/skills/hoogle/scripts/hoogle-init-db.sh --local /path/to/haddock/docs

Common Search Patterns

Goal	Query Example
Find function by name	filter
Find by exact type	(a -> Bool) -> [a] -> [a]
Find in specific package	+lens view
Find class methods	Monad m => m a -> m b
Find by partial type	Map k v -> k -> Maybe v

Error Handling

If searches fail with database errors, regenerate the database:

.codex/skills/hoogle/scripts/hoogle-init-db.sh --force

If local search cannot work, use remote search or Hoogle's JSON endpoint:

https://hoogle.haskell.org/?hoogle=<URL_ENCODED_QUERY>&mode=json