File "session"

This file provides a Prolog REPL aka top-level. The top-level can be started via the predicate prolog/0. It will repeatedly shows a prompt “?- “, read a query and show the answer substitutions until end_of_file is reached. The prompt can be used to issue Prolog commands such as the make/0 utility, that automatically reconsults modified files.

The file also provides an interactive debugger. The interactive debugger can be invoked by the recognized top-level command trace/0. The interactive debugger is implemented by means of meta programming and therefore might executed slower than call/1. As a main feature it allows inspecting the Byrd Box model by interactive prompts at the ports.

The following session predicates are provided:

abort:

The predicate signals to abort the current query.

exit:

The predicate signals to abort the current session.

make:

The predicate ensures that all used Prolog text sources are reloaded if their last modified has changed, or removed if they are not anymore used

version:

The predicate succeeds. As a side effect, a banner is printed.

prolog:

The predicate succeeds. As a side effect, a REPL is run. The following commands are available upon a port prompt:

;⏎: Creep to next port or answer substitution.

⏎: Terminate the current query.

The following top-level commands are recognized:

trace: (top-level command)

When used as a first goal in the top-level the subsequent goals are run inside an interactive Byrd Box debugger. The port prompts show the current goal using the variable names from the top-level. The following commands are then available:

a⏎: Abort the debugger and return to top-level.

l⏎: Leap to the next answer substitution.

s⏎: Skip to the next port of the current goal.

⏎: Creep to next port or answer substitution.

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