SWI-Prolog -- set_breakpoint

/usr/lib/swipl/library/prolog_breakpoints.pl

swipl
- library

set_breakpoint_condition(+Id, +Cond) is det

Set a condition for of the breakpoint with given Id. The condition Cond is a string that represents a Prolog goal to be invoked whenever the breakpoint is reached, if goal fails the breakpoint is skipped and execution commences normally.

Variables in Cond that match by name to variables in the source definition of the clause in which the breakpoint is located are unified with the corresponding runtime value of the clause variables in the current execution frame, before evaluating the condition goal.

Errors: - existence_error(breakpoint, Id).