prolog_breakpoints.pl -- Manage Prolog break-points
This module provides an interface for development tools to set and delete break-points, giving a location in the source. Development tools that want to track changes to breakpoints must use user:message_hook/3 to intercept these message terms:
breakpoint(set, Id)breakpoint(delete, Id)
Note that the hook must fail after creating its side-effects to give other hooks the opportunity to react.
- set_breakpoint(+File, +Line, +Char, -Id) is det
- set_breakpoint(+Owner, +File, +Line, +Char, -Id) is det
- Put a breakpoint at the indicated source-location. File is a current
sourcefile (as reported by source_file/1). Line is the 1-based line
in which Char is. Char is the position of the break.
First, '$clause_from_source'/4 uses the SWI-Prolog clause-source information to find the last clause starting before Line. '$break_pc' generated (on backtracking), a list of possible break-points.
Note that in addition to setting the break-point, the system must be in debug mode for the breakpoint to take effect. With threading enabled, there are various different ways this may be done. See debug/0, tdebug/0 and tdebug/1. Therefore, this predicate does not enable debug mode.
- delete_breakpoint(+Id) is det
- Delete breakpoint with given Id. If successful,
print_message(breakpoint(delete, Id))is called. Message hooks working on this message may still call breakpoint_property/2. - breakpoint_property(?Id, ?Property) is nondet
- True when Property is a property of the breakpoint Id. Defined
properties are:
- file(File)
- Provided if the breakpoint is in a clause associated to a file. May not be known.
- line_count(Line)
- Line of the breakpoint. May not be known.
- character_range(Start, Len)
- One-based character offset of the break-point. May not be known.
- clause(Reference)
- Reference of the clause in which the breakpoint resides.
Undocumented predicates
The following predicates are exported, but not or incorrectly documented.