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|Trace Mode Commands When Paused|
You can do way more than just press
spacebar when the
tracer is paused at a port. All actions are single-character commands
which are executed
without waiting for a return (unless the command line option
--no-tty is active). Pressing
when paused will print out a list of these commands as well.
Abort a Abort Prolog execution (see abort/0) Break b Enter a Prolog break environment (see break/0) Creep c Continue execution, stop at next port. (Also
Exit e Terminate Prolog (see halt/0) Fail f Force failure of the current goal Find / Search for a port (see below for the description of this command (section 220.127.116.11)) Ignore i Ignore the current goal, pretending it succeeded Leap l Continue execution, stop at next spy point No debug n Continue execution in’no debug' mode Repeat find . Repeat the last find command (see’Find' (section 18.104.22.168)) Retry r Undo all actions (except for database and I/O actions) back to the
callport of the current goal and resume execution at the
Skip s Continue execution, stop at the next port of this goal (thus skipping all calls to children of this goal) Spy + Set a spy point (see spy/1) on the current predicate. Spy points are described later in the overview (section 2.10.6). No spy - Remove the spy point (see nospy/1) from the current predicate. Spy points are described later in the overview (section 2.10.6). Up u Continue execution, stop at the next port of the parent goal (thus skipping this goal and all calls to children of this goal). This option is useful to stop tracing a failure driven loop.
) Description and Examples
The Find (
/) command continues execution until a port
matching a find pattern is found. After the
/, the user can
enter a line to specify the port to search for. This line consists of a
set of letters indicating the port type, followed by an optional term,
that should unify with the goal run by the port. If no term is specified
it is taken as a variable, searching for any port of the specified type.
If an atom is given, any goal whose functor has a name equal to that
atom matches. Examples:
/f Search for any
/fe solve Search for a
exitport of any goal with name
Search for a call to solve/2 whose first argument is a variable or the atom
Search for any port on member/2. This is equivalent to setting a spy point on member/2.
Alternatives A Show all goals that have alternatives Goals g Show the list of parent goals (the execution stack). Note that due to tail recursion optimization a number of parent goals might not exist any more. Help h Show available options (also
Listing L List the current predicate with listing/1
Context C Toggle’Show Context'. If
on, the context module of the goal is displayed between square brackets (see modules section (section 6)). Default is
Display d Set the
max_depth(Depth)option of debugger_write_options (section 2.12), limiting the depth to which terms are printed. See also the
p Set the Prolog flag debugger_write_options to
[quoted(true), portray(true), max_depth(10), priority(699)]. This is the default.
Write w Set the Prolog flag debugger_write_options to
[quoted(true), attributes(write), priority(699)], bypassing portray/1, etc.