scheme48(1) a Scheme interpreter


scheme48 [-i image] [-h heapsize] [-a argument]


scheme48 is an implementation of the Scheme programming language as described in the Revised^5 Report on the Algorithmic Language Scheme. A runnable system requires two parts, an executable program that implements the Scheme 48 virtual machine, and an image that is used to initialize the store of the virtual machine. scheme48 is a shell script that starts the virtual machine with an image that runs in a Scheme command loop.

The scheme48 command loop reads Scheme expressions, evaluates them, and prints their results. It also executes commands, which are identified by an initial comma character. Type the command ,help to receive a list of available commands.

The meaning of the -h option depends on the type of garbage collector that was chosen at configuration time. If heapsize is a positive number, it specifies the number of words that can be live at any given time. One word is four bytes. Cons cells are currently 3 words, so if you want to make sure you can allocate, say, a million cons cells, you should specify -h 3000000 (actually a little more, to account for the initial heap image and breathing room).

If you specify a maximum smaller than the memory needed to load the image file, the maximum is increased accordingly and a message is written to the console.

For the BIBOP garbage collector, heapsize may be 0. This means the heap will possibly keep growing until your system runs out of memory. Because of this risk, a warning message is written to the console if you specify -h 0.

The ,dump and ,build commands put heap images in files. The -i option causes the initial heap image to be taken from file image. The -a option causes a list of strings to be passed as the argument to an image generated using the ,build command. The first argument to ,build is a procedure that is passed the arguments following -a and which should return an integer (which is the return value of the Scheme 48 process).

     > ,build (lambda (a) (display a) (newline) 0) foo.image
     > ,exit
     $ scheme48 -i foo.image -a mumble


the virtual machine.
the default image.