.. index:: single: toychrdb .. _toychrdb/0:

.. rst-class:: right

object

toychrdb

Simple CHR interpreter/debugger based on the refined operational semantics of CHRs.

| Availability: | logtalk_load(toychr(loader))

| Author: Gregory J. Duck; adapted to Logtalk by Paulo Moura. | Version: 0:8:0 | Date: 2026-08-10

| Copyright: Copright 2004 Gregory J. Duck; Copyright 2019-2024 Paulo Moura | License: GPL-2.0-or-later

| Compilation flags: | static, context_switching_calls

| Implements: | public :ref:`expanding <expanding/0>` | Uses: | :ref:`list <list/0>` | :ref:`user <user/0>`

| Remarks: | (none)

| Inherited public predicates: | Â :ref:`expanding/0::goal_expansion/2` Â :ref:`expanding/0::term_expansion/2` Â

.. contents:: :local: :backlinks: top

Public predicates

.. index:: chr_is/2 .. _toychrdb/0::chr_is/2:

chr_is/2 ^^^^^^^^^^^^

Runs a goal against the entity CHR program and returns the resulting constraint store as a conjunction.

| Compilation flags: | static

| Template: | chr_is(Result,Goal) | Mode and number of proofs: | chr_is(?nonvar,+callable) - zero_or_one

---

.. index:: chr_trace/0 .. _toychrdb/0::chr_trace/0:

chr_trace/0 ^^^^^^^^^^^^^^^

Enables the CHR interactive trace debugger. Similar to the trace/0 standard predicate.

| Compilation flags: | static

| Mode and number of proofs: | chr_trace - one

---

.. index:: chr_notrace/0 .. _toychrdb/0::chr_notrace/0:

chr_notrace/0 ^^^^^^^^^^^^^^^^^

Disables the CHR interactive trace debugger. Similar to the notrace/0 standard predicate.

| Compilation flags: | static

| Mode and number of proofs: | chr_notrace - one

---

.. index:: chr_spy/1 .. _toychrdb/0::chr_spy/1:

chr_spy/1 ^^^^^^^^^^^^^

Sets a spy point on the activation of constraints matching the given pattern.

| Compilation flags: | static

| Template: | chr_spy(Pattern) | Mode and number of proofs: | chr_spy(@callable) - one

---

.. index:: chr_nospy/0 .. _toychrdb/0::chr_nospy/0:

chr_nospy/0 ^^^^^^^^^^^^^^^

Disables all spy points.

| Compilation flags: | static

| Mode and number of proofs: | chr_nospy - one

---

.. index:: chr_no_spy/1 .. _toychrdb/0::chr_no_spy/1:

chr_no_spy/1 ^^^^^^^^^^^^^^^^

Not yet implemented; disables the spy point on constraints matching the given pattern.

| Compilation flags: | static

| Template: | chr_no_spy(Pattern) | Mode and number of proofs: | chr_no_spy(@callable) - zero

---

.. index:: chr_option/2 .. _toychrdb/0::chr_option/2:

chr_option/2 ^^^^^^^^^^^^^^^^

Sets a debugger or compiler option. See the file documentation for the supported options and their values.

| Compilation flags: | static

| Template: | chr_option(Option,Value) | Mode and number of proofs: | chr_option(+atom,+atom) - zero_or_one

---

Protected predicates

.. index:: current_prog/1 .. _toychrdb/0::current_prog/1:

current_prog/1 ^^^^^^^^^^^^^^^^^^

Compiled CHR program generated from the entity chr_constraint, handler, and rules terms.

| Compilation flags: | static

| Template: | current_prog(Program) | Mode and number of proofs: | current_prog(?callable) - zero_or_one

---

.. index:: chr_option_print_trace/0 .. _toychrdb/0::chr_option_print_trace/0:

chr_option_print_trace/0 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

True when trace printing is enabled.

| Compilation flags: | dynamic

| Mode and number of proofs: | chr_option_print_trace - zero_or_one

---

.. index:: chr_option_trace_interactive/0 .. _toychrdb/0::chr_option_trace_interactive/0:

chr_option_trace_interactive/0 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

True when interactive tracing is enabled.

| Compilation flags: | dynamic

| Mode and number of proofs: | chr_option_trace_interactive - zero_or_one

---

.. index:: chr_option_optimization_level/1 .. _toychrdb/0::chr_option_optimization_level/1:

chr_option_optimization_level/1 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Current compiler optimization level.

| Compilation flags: | dynamic

| Template: | chr_option_optimization_level(Level) | Mode and number of proofs: | chr_option_optimization_level(?integer) - zero_or_one

---

.. index:: chr_option_show_stack/0 .. _toychrdb/0::chr_option_show_stack/0:

chr_option_show_stack/0 ^^^^^^^^^^^^^^^^^^^^^^^^^^^

True when the execution stack is shown while tracing.

| Compilation flags: | dynamic

| Mode and number of proofs: | chr_option_show_stack - zero_or_one

---

.. index:: chr_option_show_store/0 .. _toychrdb/0::chr_option_show_store/0:

chr_option_show_store/0 ^^^^^^^^^^^^^^^^^^^^^^^^^^^

True when the constraint store is shown while tracing.

| Compilation flags: | dynamic

| Mode and number of proofs: | chr_option_show_store - zero_or_one

---

.. index:: chr_option_show_history/0 .. _toychrdb/0::chr_option_show_history/0:

chr_option_show_history/0 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

True when the propagation history is shown while tracing.

| Compilation flags: | dynamic

| Mode and number of proofs: | chr_option_show_history - zero_or_one

---

.. index:: chr_option_show_id/0 .. _toychrdb/0::chr_option_show_id/0:

chr_option_show_id/0 ^^^^^^^^^^^^^^^^^^^^^^^^

True when the current constraint identifier is shown while tracing.

| Compilation flags: | dynamic

| Mode and number of proofs: | chr_option_show_id - zero_or_one

---

.. index:: chr_option_allow_deep_guards/0 .. _toychrdb/0::chr_option_allow_deep_guards/0:

chr_option_allow_deep_guards/0 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

True when CHR constraints are allowed in rule guards or if-conditions.

| Compilation flags: | dynamic

| Mode and number of proofs: | chr_option_allow_deep_guards - zero_or_one

---

.. index:: chr_next_state/1 .. _toychrdb/0::chr_next_state/1:

chr_next_state/1 ^^^^^^^^^^^^^^^^^^^^

Stack length recorded to detect when the next debugger step is reached.

| Compilation flags: | dynamic

| Template: | chr_next_state(Length) | Mode and number of proofs: | chr_next_state(?integer) - zero_or_one

---

.. index:: chr_spy_point/1 .. _toychrdb/0::chr_spy_point/1:

chr_spy_point/1 ^^^^^^^^^^^^^^^^^^^

Asserted clause matching constraints on which a spy point is set.

| Compilation flags: | dynamic

| Template: | chr_spy_point(Constraint) | Mode and number of proofs: | chr_spy_point(@callable) - zero_or_more

---

Private predicates

.. index:: chr_rule_/1 .. _toychrdb/0::chr_rule_/1:

chr_rule_/1 ^^^^^^^^^^^^^^^

Asserted CHR rule term collected during term-expansion, consumed when compiling the entity program.

| Compilation flags: | dynamic

| Template: | chr_rule_(Rule) | Mode and number of proofs: | chr_rule_(?callable) - zero_or_more

---

Operators

(none)