GRL compiler interface

The GRL compiler is divided into a set of Scheme packages: girl-compiler, girl-top-level, and the various auxilliary back ends.  The compiler works by compiling code into an intermediate language, which is a subset of Scheme.  Intermediate language code is non-recursive and doesn't perform any run-time type checking or storage allocation.   That is to say, it might as well be C.

Compilation procedures are called with a list of roots.  Roots can be signals, lists of signals, lists of lists of signals, etc.  They're called roots because the compiler performs a depth-first search of the graph of all signals, starting from the roots.  Any signal that is encountered in the process of the walk is emitted as intermediate code.  Other signals are ignored.

Package girl-top-level

The girl-top-level package provides access to a set of procedures that allow you compile intermediate code from a list of roots.  Since they generate intermediate code, they are mostly useful for examining the code being generated by the compiler.   When compiling code for real, you will most likely use a back end tailored for your specific robot or target language.

(compile roots  ...)
Compiles roots to Scheme intermediate code and displays it on the screen or in the output file specified by the :output-file compiler option.
(compile-to-file file-name  roots  ...)
Compiles roots to Scheme intermediate code and writes it  to output-file.
(compile-and-run roots  ...)
Compiles roots to Scheme intermediate code and evals the code.  This lets you do limited testing on your desktop, or to run the girl compiler directly on your robot if it supports Scheme48.

The back ends

There are a number of back ends available for the compiler.  To use one, open its package or another package that exports it (see the release notes) and call the appropriate procedure.  Each back exports a pair of procedures, compile-to-X and compile-to-X-file, which have the same arguments as compile and compile-to-file, but happen to generate code for X.

Package girl-compiler

This package is mostly intended for programmers developing new back ends.   However, some of the options will also be useful for powerusers trying to tweak the code generated by the compiler.  The only procedure exported by the package that should be called by normal users is compiler-options.   It takes a list of keywords and values, a la Common Lisp.

User-level compiler options

:clock-period
:clock-frequncy
Specifies target frequency of main command loop.
:force-expression
Prevents inlining of some or all signals.  If #t, then no signals are inlined.   If 'roots, then only the signals specfied in the call the compiler will be prevented from being inlined.
:target-procedure-name
The name of the procedure that will contain the main while loop.
:temp-name-prefix
A string to be prepended to every temporary variable generated by the compiler.   Used to prevent name collisions when two different programs generated by the compiler are to be run in parallel.

Mostly used for compiler debugging

:show-raw-intermediate-code
Compiler pretty-prints Scheme intermediate code before partial evaluation.
:show-partially-evaluated-code
Compiler pretty-prints Scheme intermediate code after partial evaluation.
:show-expanded-signals
Compiles displays list of all signals encountered during its inital walk of the signal graph.
:show-sorted-signals
Compiles displays final sorted list of all primitive signals for which code is to be generated.

Internal compiler options

:code-printer
The procedure called to print the intermediate code
:output-file
The file to write the code to.  #f means write it to the screen.
:typed-declarations
Whether to add type information to variable declarations in the intermediate code
:global-variables
Forces all variables to be global
:generate-debug-info
Whether extra debugging information should be added to the object code
:generate-while-loop
Whether the code should be wrapped in a while loop
:never-inline-conditionals
Prevents if and nth calls from ever being inlined
:generate-lets
If false, lets will be changed into applications of lambdas.
:flatten-conditionals
Prevents if from being placed in an subexpressions.
:expand-cond
:expand-case
:expand-when-and-unless
Whether these should be translated into ifs.
:report-cycles
Whether the compiler should tell you about cycles in the signal graph