Friday, March 17, 2006

Mixing Scheme and C

In my quest to find the perfect Scheme/C mix I've found that Bigloo Scheme really goes a long way to overcome the language barriers. The cool part is that Bigloo compiles to efficient C code, and you can influence the generated code in a number of ways. For example, it's possible to include headers and declare functions with type annotations straight in the Scheme source code. Since the Scheme files are translated to C when compiled, there's no marshalling to consider. I'm assuming that annotated procedures yield a very low overhead compared to Python which requires a object allocations for everything (even integers). Using Bigloo with DLLs symbols on windows has one quirk though, the symbols must be imported as macros, and the header file with _declspec() crud must be included explicitly. This does the trick:
(module my-module
          (include "include/mydll.h")
          (macro simple::int (::int) "simple")))
Given these declarations, you can call the function simple as if it were a Scheme procedure, which is awesome. When compiled, the resulting executable links properly to the DLL. I haven't found a tool that can produce these annotations automatically, but writing one should be trivial. I'm slightly confused about how to make a stringent build system for a combined Scheme/C project, but I'm sure it's possible. Armed with such a build tool it might actually become fun to program again..

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