Usage:

    $$ [command-line-options-and-input-files]

To compile and link a complete Haskell program, run the compiler like
so:

    $$ Main

where the module Main is in a file named Main.hs (or Main.lhs) in the
current directory.  The other modules in the program will be located
and compiled automatically, and the linked program will be placed in
the file `Main' (or `Main.exe' on Windows).

Alternatively, $$ can be used to compile files individually.  Each
input file is guided through (some of the) possible phases of a
compilation:

    - unlit:	extract code from a "literate program"
    - hscpp:	run code through the C pre-processor (if -cpp flag given)
    - hsc:	run the Haskell compiler proper
    - gcc:	run the C compiler (if compiling via C)
    - as:	run the assembler
    - ld:	run the linker

For each input file, the phase to START with is determined by the
file's suffix:

    - .lhs	literate Haskell		 unlit
    - .hs	plain Haskell			 ghc
    - .hc	C from the Haskell compiler	 gcc
    - .c	C not from the Haskell compiler  gcc
    - .s	assembly language		 as
    - other	passed directly to the linker	 ld

The phase at which to STOP processing is determined by a command-line
option:

    -E		stop after generating preprocessed, de-litted Haskell
		     (used in conjunction with -cpp)
    -C		stop after generating C (.hc output)
    -S		stop after generating assembler (.s output)
    -c		stop after generating object files (.o output)

Other commonly-used options are:

    -v[n]	    Control verbosity (n is 0--5, normal verbosity level is 1,
	              -v alone is equivalent to -v3)

    -O		    An `optimising' package of compiler flags, for faster code

    -prof	    Compile for cost-centre profiling
		     (add -auto-all for automagic cost-centres on all
		      top-level functions)

    -H14m	    Increase compiler's heap size (might make compilation
		    faster, especially on large source files).

    -M              Output Makefile rules recording the
		    dependencies of a list of Haskell files.

Given the above, here are some TYPICAL invocations of $$:

    # compile a Haskell module to a .o file, optimising:
    % $$ -c -O Foo.hs
    # link three .o files into an executable called "test":
    % $$ -o test Foo.o Bar.o Baz.o
    # compile a Haskell module to C (a .hc file), using a bigger heap:
    % $$ -C -H16m Foo.hs
    # compile Haskell-produced C (.hc) to assembly language:
    % $$ -S Foo.hc

The User's Guide has more information about GHC's *many* options.  An
online copy can be found here:

   http://www.haskell.org/ghc/docs/latest/html/users_guide/

If you *really* want to see every option, then you can pass
'--show-options' to the compiler.

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