The Glorious Glasgow Haskell Compilation System User's Guide, Version 6.8.2

The GHC Team

Table of Contents

The Glasgow Haskell Compiler License
1. Introduction to GHC
1.1. Meta-information: Web sites, mailing lists, etc.
1.2. Reporting bugs in GHC
1.3. GHC version numbering policy
1.4. Release notes for version 6.8.2
1.5. Release notes for version 6.8.1
1.5.1. User-visible compiler changes
1.5.2. Profiling changes
1.5.3. GHCi changes
1.5.4. Boot Libraries array base bytestring Cabal containers directory filepath haskell98 hpc old-locale old-time packedstring pretty process random readline template-haskell unix Win32
1.5.5. GHC As A Library
2. Installing GHC
2.1. Installing on Unix-a-likes
2.1.1. When a platform-specific package is available
2.1.2. GHC binary distributions Installing Testing that GHC seems to be working
2.2. Installing on Windows
2.2.1. Installing GHC on Windows
2.2.2. Moving GHC around
2.2.3. Installing ghc-win32 FAQ
2.3. The layout of installed files
2.3.1. The binary directory
2.3.2. The library directory
3. Using GHCi
3.1. Introduction to GHCi
3.2. Loading source files
3.2.1. Modules vs. filenames
3.2.2. Making changes and recompilation
3.3. Loading compiled code
3.4. Interactive evaluation at the prompt
3.4.1. I/O actions at the prompt
3.4.2. Using do-notation at the prompt
3.4.3. What's really in scope at the prompt? Qualified names The :main command
3.4.4. The it variable
3.4.5. Type defaulting in GHCi
3.5. The GHCi Debugger
3.5.1. Breakpoints and inspecting variables Setting breakpoints Listing and deleting breakpoints
3.5.2. Single-stepping
3.5.3. Nested breakpoints
3.5.4. The _result variable
3.5.5. Tracing and history
3.5.6. Debugging exceptions
3.5.7. Example: inspecting functions
3.5.8. Limitations
3.6. Invoking GHCi
3.6.1. Packages
3.6.2. Extra libraries
3.7. GHCi commands
3.8. The :set command
3.8.1. GHCi options
3.8.2. Setting GHC command-line options in GHCi
3.9. The .ghci file
3.10. Compiling to object code inside GHCi
3.11. FAQ and Things To Watch Out For
4. Using runghc
4.1. Flags
5. Using GHC
5.1. Options overview
5.1.1. Command-line arguments
5.1.2. Command line options in source files
5.1.3. Setting options in GHCi
5.2. Static, Dynamic, and Mode options
5.3. Meaningful file suffixes
5.4. Modes of operation
5.4.1. Using ghc ––make
5.4.2. Expression evaluation mode
5.4.3. Batch compiler mode Overriding the default behaviour for a file
5.5. Help and verbosity options
5.6. Filenames and separate compilation
5.6.1. Haskell source files
5.6.2. Output files
5.6.3. The search path
5.6.4. Redirecting the compilation output(s)
5.6.5. Keeping Intermediate Files
5.6.6. Redirecting temporary files
5.6.7. Other options related to interface files
5.6.8. The recompilation checker
5.6.9. How to compile mutually recursive modules
5.6.10. Using make
5.6.11. Dependency generation
5.6.12. Orphan modules and instance declarations
5.7. Warnings and sanity-checking
5.8. Packages
5.8.1. Using Packages
5.8.2. The main package
5.8.3. Consequences of packages
5.8.4. Package Databases The GHC_PACKAGE_PATH environment variable
5.8.5. Building a package from Haskell source
5.8.6. Package management (the ghc-pkg command)
5.8.7. InstalledPackageInfo: a package specification
5.9. Optimisation (code improvement)
5.9.1. -O*: convenient “packages” of optimisation flags.
5.9.2. -f*: platform-independent flags
5.10. Options related to a particular phase
5.10.1. Replacing the program for one or more phases
5.10.2. Forcing options to a particular phase
5.10.3. Options affecting the C pre-processor CPP and string gaps
5.10.4. Options affecting a Haskell pre-processor
5.10.5. Options affecting the C compiler (if applicable)
5.10.6. Options affecting code generation
5.10.7. Options affecting linking
5.11. Using Concurrent Haskell
5.12. Using SMP parallelism
5.12.1. Options to enable SMP parallelism
5.12.2. Hints for using SMP parallelism
5.13. Platform-specific Flags
5.14. Running a compiled program
5.14.1. Setting global RTS options
5.14.2. Miscellaneous RTS options
5.14.3. RTS options to control the garbage collector
5.14.4. RTS options for profiling and parallelism
5.14.5. RTS options for hackers, debuggers, and over-interested souls
5.14.6. “Hooks” to change RTS behaviour
5.14.7. Getting information about the RTS
5.15. Generating and compiling External Core Files
5.16. Debugging the compiler
5.16.1. Dumping out compiler intermediate structures
5.16.2. Checking for consistency
5.16.3. How to read Core syntax (from some -ddump flags)
5.16.4. Unregisterised compilation
5.17. Flag reference
5.17.1. Help and verbosity options
5.17.2. Which phases to run
5.17.3. Alternative modes of operation
5.17.4. Redirecting output
5.17.5. Keeping intermediate files
5.17.6. Temporary files
5.17.7. Finding imports
5.17.8. Interface file options
5.17.9. Recompilation checking
5.17.10. Interactive-mode options
5.17.11. Packages
5.17.12. Language options
5.17.13. Warnings
5.17.14. Optimisation levels
5.17.15. Individual optimisations
5.17.16. Profiling options
5.17.17. Program coverage options
5.17.18. Haskell pre-processor options
5.17.19. C pre-processor options
5.17.20. C compiler options
5.17.21. Code generation options
5.17.22. Linking options
5.17.23. Replacing phases
5.17.24. Forcing options to particular phases
5.17.25. Platform-specific options
5.17.26. External core file options
5.17.27. Compiler debugging options
5.17.28. Misc compiler options
6. Profiling
6.1. Cost centres and cost-centre stacks
6.1.1. Inserting cost centres by hand
6.1.2. Rules for attributing costs
6.2. Compiler options for profiling
6.3. Time and allocation profiling
6.4. Profiling memory usage
6.4.1. RTS options for heap profiling
6.4.2. Retainer Profiling Hints for using retainer profiling
6.4.3. Biographical Profiling
6.4.4. Actual memory residency
6.5. hp2ps––heap profile to PostScript
6.5.1. Manipulating the hp file
6.5.2. Zooming in on regions of your profile
6.5.3. Viewing the heap profile of a running program
6.5.4. Viewing a heap profile in real time
6.6. Observing Code Coverage
6.6.1. A small example: Reciprocation
6.6.2. Options for instrumenting code for coverage
6.6.3. The hpc toolkit hpc report hpc markup hpc sum hpc combine hpc map hpc overlay and hpc draft
6.6.4. Caveats and Shortcomings of Haskell Program Coverage
6.7. Using “ticky-ticky” profiling (for implementors)
7. Advice on: sooner, faster, smaller, thriftier
7.1. Sooner: producing a program more quickly
7.2. Faster: producing a program that runs quicker
7.3. Smaller: producing a program that is smaller
7.4. Thriftier: producing a program that gobbles less heap space
8. GHC Language Features
8.1. Language options
8.2. Unboxed types and primitive operations
8.2.1. Unboxed types
8.2.2. Unboxed Tuples
8.3. Syntactic extensions
8.3.1. Hierarchical Modules
8.3.2. Pattern guards
8.3.3. The recursive do-notation
8.3.4. Parallel List Comprehensions
8.3.5. Rebindable syntax
8.3.6. Postfix operators
8.3.7. Record field disambiguation
8.4. Extensions to data types and type synonyms
8.4.1. Data types with no constructors
8.4.2. Infix type constructors, classes, and type variables
8.4.3. Liberalised type synonyms
8.4.4. Existentially quantified data constructors Why existential? Existentials and type classes Record Constructors Restrictions
8.4.5. Declaring data types with explicit constructor signatures
8.4.6. Generalised Algebraic Data Types (GADTs)
8.5. Extensions to the "deriving" mechanism
8.5.1. Inferred context for deriving clauses
8.5.2. Stand-alone deriving declarations
8.5.3. Deriving clause for classes Typeable and Data
8.5.4. Generalised derived instances for newtypes Generalising the deriving clause A more precise specification
8.6. Class and instances declarations
8.6.1. Class declarations Multi-parameter type classes The superclasses of a class declaration Class method types
8.6.2. Functional dependencies Rules for functional dependencies Background on functional dependencies
8.6.3. Instance declarations Relaxed rules for instance declarations Undecidable instances Overlapping instances Type synonyms in the instance head
8.6.4. Overloaded string literals
8.7. Other type system extensions
8.7.1. Type signatures The context of a type signature
8.7.2. Implicit parameters Implicit-parameter type constraints Implicit-parameter bindings Implicit parameters and polymorphic recursion Implicit parameters and monomorphism
8.7.3. Explicitly-kinded quantification
8.7.4. Arbitrary-rank polymorphism Examples Type inference Implicit quantification
8.7.5. Impredicative polymorphism
8.7.6. Lexically scoped type variables Overview Declaration type signatures Expression type signatures Pattern type signatures Class and instance declarations
8.7.7. Generalised typing of mutually recursive bindings
8.7.8. Type families
8.8. Template Haskell
8.8.1. Syntax
8.8.2. Using Template Haskell
8.8.3. A Template Haskell Worked Example
8.8.4. Using Template Haskell with Profiling
8.9. Arrow notation
8.9.1. do-notation for commands
8.9.2. Conditional commands
8.9.3. Defining your own control structures
8.9.4. Primitive constructs
8.9.5. Differences with the paper
8.9.6. Portability
8.10. Bang patterns
8.10.1. Informal description of bang patterns
8.10.2. Syntax and semantics
8.11. Assertions
8.12. Pragmas
8.12.1. LANGUAGE pragma
8.12.2. OPTIONS_GHC pragma
8.12.3. INCLUDE pragma
8.12.4. DEPRECATED pragma
8.12.5. INLINE and NOINLINE pragmas INLINE pragma NOINLINE pragma Phase control
8.12.6. LINE pragma
8.12.7. RULES pragma
8.12.8. SPECIALIZE pragma
8.12.9. SPECIALIZE instance pragma
8.12.10. UNPACK pragma
8.13. Rewrite rules
8.13.1. Syntax
8.13.2. Semantics
8.13.3. List fusion
8.13.4. Specialisation
8.13.5. Controlling what's going on
8.13.6. CORE pragma
8.14. Special built-in functions
8.15. Generic classes
8.15.1. Using generics
8.15.2. Changes wrt the paper
8.15.3. Terminology and restrictions
8.15.4. Another example
8.16. Control over monomorphism
8.16.1. Switching off the dreaded Monomorphism Restriction
8.16.2. Monomorphic pattern bindings
8.17. Concurrent and Parallel Haskell
8.17.1. Concurrent Haskell
8.17.2. Software Transactional Memory
8.17.3. Parallel Haskell
8.17.4. Annotating pure code for parallelism
9. Foreign function interface (FFI)
9.1. GHC extensions to the FFI Addendum
9.1.1. Unboxed types
9.1.2. Newtype wrapping of the IO monad
9.2. Using the FFI with GHC
9.2.1. Using foreign export and foreign import ccall "wrapper" with GHC Using your own main() Making a Haskell library that can be called from foreign code On the use of hs_exit()
9.2.2. Using function headers Finding Header files
9.2.3. Memory Allocation
10. What to do when something goes wrong
10.1. When the compiler “does the wrong thing”
10.2. When your program “does the wrong thing”
11. Other Haskell utility programs
11.1. Ctags and Etags for Haskell: hasktags
11.1.1. Using tags with your editor
11.2. “Yacc for Haskell”: happy
11.3. Writing Haskell interfaces to C code: hsc2hs
11.3.1. command line syntax
11.3.2. Input syntax
11.3.3. Custom constructs
12. Running GHC on Win32 systems
12.1. Starting GHC on Windows platforms
12.2. Running GHCi on Windows
12.3. Interacting with the terminal
12.4. Differences in library behaviour
12.5. Using GHC (and other GHC-compiled executables) with cygwin
12.5.1. Background
12.5.2. The problem
12.5.3. Things to do
12.6. Building and using Win32 DLLs
12.6.1. Creating a DLL
12.6.2. Making DLLs to be called from other languages
12.6.3. Beware of DllMain()!
13. Known bugs and infelicities
13.1. Haskell 98 vs. Glasgow Haskell: language non-compliance
13.1.1. Divergence from Haskell 98 Lexical syntax Context-free syntax Expressions and patterns Declarations and bindings Module system and interface files Numbers, basic types, and built-in classes In Prelude support
13.1.2. GHC's interpretation of undefined behaviour in Haskell 98
13.2. Known bugs or infelicities
13.2.1. Bugs in GHC
13.2.2. Bugs in GHCi (the interactive GHC)