138 lines
4.5 KiB
Plaintext
138 lines
4.5 KiB
Plaintext
The interaction library currently offers three structures that provide
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a programmatic interface to Scheme 48's debugging facilities:
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* REPLS starts the read-eval-print-loop with arbitrary input and
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output ports.
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* INSPECT-EXCEPTION provides exception handlers that allow interactive
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inspection of exceptions and their backtrace.
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* GC provides a small run-time interface to the garbage collector.
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The structure REPLS offers procedures to start up the
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read-eval-print-loop (REPL) from a script.
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(script-repl greeting focus-value iport oport eport)
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This procedure starts up a new REPL which greets the user with
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GREETING, has FOCUS-VALUE as initial focus-value (accessible through
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##) and uses the ports IPORT for input, OPORT for output and eport for
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error messages.
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(remote-repl greeting focus-value port)
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Same as above but communication is done via a socket on port PORT.
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The structure SOCKET2STDPORTS offers a very simple facility to map the
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current input and output ports to the ports of a socket.
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(socket<->stdports host port)
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This procedure first establishes a TCP socket to port PORT on host
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HOST. Afterwards is reads all data from (current-input-port) and
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forwards it into the socket's input port. Likewise it reads all data
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from the socket's output port and prints it to
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(current-output-port).
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The structure INSPECT-EXCEPTION makes some of the functionality of the
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,debug and ,preview commands available.
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(with-inspecting-handler port prepare thunk)
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This procedure installs a exception handler which captures all
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conditions which satisfy the predicate ERROR?. In case of an exception
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PREPARE is applied to the condition. If it returns #t,
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WITH-INSPECTING-HANDLER will fire up a remote REPL on port PORT with
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the continuation of the condition as focus value. Currently, the
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continuation of the REPL is the continuation of the call to
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WITH-INSPECTING-HANDLER. If PREPARE returns #f the surrounding handler
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is called.
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As an example for the usage of the remote inspecting utility, consider
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a program using WITH-INSPECTING-HANDLER with an obviously bogus body:
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>(with-inspecting-handler 8080
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(lambda (cond) (display "Help me on port 8080") #t)
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(lambda () (/ 1 0)))
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Help me on port 8080
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Now start a second scsh:
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[0 gasbichl@ventoux interaction] scsh -lm interfaces.scm -lm packages.scm -o 'socket2stdports'
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Welcome to scsh 0.6.3
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Type ,? for help.
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> (socket<->stdports "ventoux" 8080)
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Welcome to the command processor of the remote scsh
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#{Exception-continuation (pc 69) (integer/ in ratnums)}
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> ,debug
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'#{Exception-continuation (pc 69) (integer/ in ratnums)}
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[0] 1
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[1] 0
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inspect: d
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'#{Exception-continuation (pc 15) (/ in scheme-level-0)}
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inspect: d
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'#{Continuation (pc 13) (unnamed in unnamed in unnamed ---)}
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[0] '#{Procedure 1319 (unnamed in continuation->procedure in wind)}
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[1: k] '#{Procedure 1319 (unnamed in continuation->procedure in wind)}
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[2: accept] '#{Procedure 1319 (unnamed in continuation->procedure in wind)}
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[3: handler] '#{Procedure 14367 (unnamed in with-inspecting-handler in inspect-exception)}
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[4: thunk] '#{Procedure 14379}
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inspect: ,go 34
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Terminating command processor with value 34
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Unfortunately, SOCKET<->STD-PORTS is currently not able to exit
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gracefully if the connection dies:
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Error: exception
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os-error
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(channel-maybe-write 32 '#{Byte-vector 10} 0 1 '#{Output-channel 4} ---)
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WARNING: Returning does not work from a scsh with a running REPL!!!
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(with-fatal-and-capturing-error-handler handler thunk)
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An exception handler with allows to capture the continuation of the
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exception. Here HANDLER is a procedure like
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(handler condition continuation decline) -> val
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CONDITION and DECLINE are the same as in the usual WITH-HANDLER
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procedure. CONTINUATION represents the continuation of the
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exception. However, this is not a procedure but the VM's continuation
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object. The continuation of HANDLER is the continuation of
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WITH-FATAL-AND-CAPTURING-ERROR-HANDLER.
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(display-continuation continuation [port] -> unspecified
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The procedural analogy to the ,proceed command. Continuation must be a
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continuation object as captured by
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WITH-FATAL-AND-CAPTURING-ERROR-HANDLER, not a procedure as captured by
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CALL-WITH-CURRENT-CONTINUATION.
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The structure GC provides a procedure equivalent to the ,collect
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command and offers some statistics about the garbage collector.
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(collect outport) -> unspecified
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Invokes the GC and prints the number of free words before and after
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the collection to OUTPORT.
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(gc-count) -> number
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Returns the number of times the garbage collector has been invoked
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since the start of the system.
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