The command processor


When you invoke the default heap image, a command processor starts running. At the > prompt, you can type either a Scheme form (expression or definition), or a command beginning with a comma.

Logistical commands

,load <filename >
Load Scheme source file(s). For example
    > ,load /home/gjs/foo.scm

Easier to type than (load "filename") because you don't have to shift to type the parentheses or quote marks. Also, it works in any package, unlike (load "filename"), which will work only work in packages in which the variable LOAD is defined properly.

,exit [<exp >]
Exit back out to shell (or executive or whatever invoked Scheme 48 in the first place). <exp > should evaluate to an integer. The integer is returned to the calling program. (On Unix, 0 is generally interpreted as success, nonzero as failure.)

Command levels

If an errors occurs, you are put in a command loop at the dynamic point at which the error occurred. The prompt will then be "n >" where n is the command level nesting depth.

Pop out one level (running any dynamic-wind "after" thunks), and resumes running all non-broken threads. EOF after a keyboard interrupt resumes running the interrupted thread. <eof> is usually control-D at a Unix shell or using the Emacs "cmuscheme48" library.

Unwind all the way back out to top level.

,level <number >
Unwind out to a given level. ,level 0 is the same as ,reset.

Go to a deeper command level. (See ,levels, below.)


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