ghci

Interactive REPL environment for Haskell

TLDR

Start interactive session

$ ghci

Load a file

$ ghci [file.hs]

Load module in session

$ :load [file.hs]

Get type of expression

$ :type [expression]

Reload current module

$ :reload

ghci is the interactive environment for GHC (Glasgow Haskell Compiler). It provides a REPL for evaluating Haskell expressions, loading modules, and exploring types interactively.GHCi supports all GHC language extensions and can compile modules on the fly. It provides introspection commands for examining types, kinds, and documentation. Tab completion and command history enhance usability.

PARAMETERS

FILES

Haskell files to load.

:load FILE

Load a module.

:reload

Reload current modules.

:type, :t EXPR

Show expression type.

:kind, :k TYPE

Show the kind of a type.

:info NAME

Show info about name, including definition and instances.

:browse MODULE

List identifiers exported by a module.

:set OPTION

Set a GHCi or compiler option for the session.

:main ARGS

Run the program's `main` with the given arguments.

:quit, :q

Exit GHCi.

-i DIR1:...:DIRn

Add directories to the source file search path.

--help

Display help information.

CONFIGURATION

~/.ghci

Per-user startup file loaded when GHCi starts, containing default settings, imports, and custom commands.

./.ghci

Project-local startup file loaded after the user file (must have safe permissions to be read).

CAVEATS

Some compiled code may behave differently in interpreter. Memory usage can grow with large expressions. Restart clears interpreter state.

HISTORY

GHCi was introduced with GHC 5.0 in 2001, providing interactive Haskell evaluation alongside the batch compiler.