Gambit Scheme Code Generator

The Gambit Scheme code generator can be accessed via the REPL command:

Main> :set cg gambit

Alternatively, you can set it via the IDRIS2_CG environment variable:

$ export IDRIS2_CG=gambit

To run Idris programs with this generator, you will need to install Gambit Scheme. Gambit Scheme is free software, and available via most package managers.

You can compile an expression expr of type IO () to an executable as follows, at the REPL:

Main> :c execname expr

…where execname is the name of the executable file. This will generate the following:

  • An executable binary build/exec/execname of the program.
  • A Gambit Scheme source file build/exec/execname.scm, from which the binary is generated.

You can also execute an expression directly:

Main> :exec expr

Again, expr must have type IO (). This will generate a temporary Scheme file, and execute the Gambit interpreter on it.

Gambit Directives

  • --directive extraRuntime=<path>

    Embed Scheme source from <path> directly into generated output. Can be specified more than once, in which case all given files will be included in the order specified.

    ; extensions.scm
    (define (my-mul a b)
      (* a b))
    
    -- Main.idr
    %foreign "scheme:my-mul"
    myMul : Int -> Int -> Int
    
    $ idris2 --codegen chez --directive extraRuntime=/path/to/extensions.scm -o main Main.idr
    
  • --directive C

    Compile to C.

Gambit Environment Configurations

  • GAMBIT_GSC_BACKEND

    The GAMBIT_GSC_BACKEND variable controls which C compiler Gambit will use during compilation. E.g. to use clang:

    $ export GAMBIT_GSC_BACKEND=clang
    

    Gambit after version v4.9.3 supports the -cc option, which configures the compiler backend Gambit will use to build the binary. Currently to get this functionality Gambit needs to be built from source, since it is not yet available in a released version.