Using the hbc compiler

The hbc command can be used to compile a module or link compiled module together.

On names, files, and modules

The Haskell report does not specify how Haskell modules, files etc. should be treated by the compilation system. Hbc takes a very simple approach, each file should contain exactly one module and the name of the file should be the same as the module name with the extension ``.hs'' added. When such a file is compiled by hbc an interface file and an object file are produced. The interface file has the same name as the source file, but with the extension ``.hi'' instead of ``.hs'', the object file has the ``.o'' extension. If the file extension is ``.lhs'' the module is assumed to be on ``literate'' form and is compiled accordingly.

When compiling an ``import'' declaration the compiler needs to consult the interface file for the imported module. To find the interface file the compiler looks for the module name extended with ``.hi'' in the include path. The include path is a colon separated list of directories that are searched in order for the imported files. The include path can be set in several ways. The default value is ``.:$HBCDIR/hbc_library'', where $HBCDIR is the value of the HBCDIR environment variable (which defaults to /usr/local/lib/lmlc if not set). If the environment variable HBCINCPATH is set this will be taken as the value of the include path instead. After this initial value of the include path has been established it can also be altered by the ``-i'' flag on the command line. Just ``-i'' flag will empty the include path. A ``-ipath'' will prepend path to the include path.

The include path is also used during linking. All files named ``lib.a'' (or ``lib_p.a'' or ``lib_ph.a'' if the ``-p'' respective ``-ph'' flags have been used) in the directories in the include path will be given to the linker. This means that a directory in the include path should contain (at least) a number of interface files, and the corresponding object files in an archive called ``lib.a''.

The interactive system uses the same mechanism for its import command. But for this to work properly the directories in the include path should also contain the object files for each of the interface files, since hbi cannot (yet) use archives.

Example

If the file ``Main.hs'' contains

  main = putStr (hello "world" ++ "\n")

  hello s = "hello, " ++ s

then it can be compiled with the command

  hbc Main.hs -o hello

This gives an executable file called ``hello''.

Last modified: Sun Jul 21 01:15:37 MET DST 1996