Merge pull request #1348 from mathics/predicate-processing

Advanced predicate processing

Author: rocky

mathics/builtin/inference.py

@@ -1,4 +1,7 @@
+# -*- coding: utf-8 -*-
+
 from mathics.version import __version__  # noqa used in loading to check consistency.
+
 from mathics.core.expression import (
     Expression,
     Symbol,
@@ -14,8 +17,103 @@
 # TODO: Extend these rules?
 
 
+def debug_logical_expr(pref, expr, evaluation):
+    pass
+    # return
+    # print(pref , expr) #expr.format(evaluation,"OutputForm").boxes_to_text(evaluation=evaluation))
+
+
+logical_algebraic_rules_spec = {
+    # Inequality rules
+    "Unequal[a_, b_]": "Not[Equal[a, b]]",
+    "Greater[a_, b_]": "Less[b, a]",
+    "GreaterEqual[a_, b_]": "Not[Less[a, b]]",
+    "LessEqual[a_, b_]": "Not[Less[b, a]]",
+    "PositiveQ[a_]": "Less[0, a]",
+    "NegativeQ[a_]": "Less[a, 0]",
+    # Logical basic reductions
+    "Or[q_, Not[q_]]": "True",
+    "Or[q_,]": "q",
+    "Or[q_, q_]": "q",
+    "Or[pred1___, q_, pred2___, q_, pred3___]": "Or[pred1, q, pred2, pred3]",
+    # TODO: Logical operations should sort the leaves...
+    "Or[Not[q_], q_]": "True",
+    "Or[pred1___, q_, pred2___, Not[q_], pred3___]": "Or[pred1, pred2, pred3]",
+    "Or[pred1___, Not[q_], pred2___, q_, pred3___]": "Or[pred1, pred2, pred3]",
+    "And[q_,q_]": "q",
+    "And[q_, Not[q_]]": "False",
+    "And[Not[q_],q_]": "False",
+    "And[pred1___, q_, pred2___, Not[q_], pred3___]": "False",
+    "And[pred1___, Not[q_], pred2___, q_, pred3___]": "False",
+    # Logical reductions involving equalities
+    "Or[pred1___, a_==b_, pred2___ , b_==a_, pred3___]": "Or[pred1, a==b, pred2, pred3]",
+    "And[pred1___, a_==b_, pred2___ , b_==a_, pred3___]": "And[pred1, a==b, pred2, pred3]",
+    "Or[pred1___, a_==b_, pred2___ , Not[b_==a_], pred3___]": "Or[pred1, pred2, pred3]",
+    "And[pred1___, a_==b_, pred2___ , Not[b_==a_], pred3___]": "False",
+    "Xor[q_,  Not[q_]]": "True",
+    "Xor[a_==b_,  Not[b_==a_]]": "True",
+    # Logical reductions involving inequalities
+    "Or[a_<b_, b_<a_]": "! (a==b)",
+    "And[a_<b_, b_<a_]": "False",
+    "Or[a_<b_, b_==a_]": "! (a>b)",
+    "Or[b_==a_, a_<b_]": "! (a>b)",
+    "And[a_<b_, b_==a_]": "False",
+    "And[b_==a_, a_<b_]": "False",
+    "And[pred1___, a_<b_, pred2___, Not[b_<a_], pred3___ ]": "And[pred1, a==b, pred2, pred3]",
+    "And[pred1___, a_<b_, pred2___, b_<a_, pred3___ ]": "False",
+    "And[pred1___, a_<b_, pred2___, b_==a_, pred3___ ]": "False",
+    "Or[pred1___, a_<b_, pred2___, b_<a_, pred3___ ]": "And[pred1,Not[a==b],pred2, pred3]",
+    "Or[pred1___, a_<b_, pred2___, b_==a_, pred3___ ]": "And[pred1,Not[b<a],pred2, pred3]",
+    "Or[pred1___, q_, pred2___, Not[q_], pred3___  ]": "Or[pred1, pred2, pred3]",
+    # Let's assume that variables are finite
+    "-Infinity< Infinity": "True",
+    "Infinity< -Infinity ": "False",
+    "Infinity == -Infinity ": "False",
+    "_Symbol < Infinity ": "True",
+    "-Infinity  <_Symbol": "True",
+}
+
+remove_not_rules_spec = {
+    "Not[a_<b_]": "a>=b",
+    "Not[a_==b_]": "a!=b",
+}
+
 
-def get_assumptions_list(evaluation): 
+logical_algebraic_rules = None
+remove_not_rules = None
+
+
+def ensure_logical_algebraic_rules():
+    global logical_algebraic_rules
+    global remove_not_rules
+    if logical_algebraic_rules is None:
+        logical_algebraic_rules = []
+        for pattern, replace in logical_algebraic_rules_spec.items():
+            pattern = parse_builtin_rule(pattern, SystemDefinitions())
+            logical_algebraic_rules.append(
+                Rule(pattern, parse_builtin_rule(replace), system=True)
+            )
+        remove_not_rules = []
+        for pattern, replace in remove_not_rules_spec.items():
+            pattern = parse_builtin_rule(pattern, SystemDefinitions())
+            remove_not_rules.append(
+                Rule(pattern, parse_builtin_rule(replace), system=True)
+            )
+    return
+
+
+def remove_nots_when_unnecesary(pred, evaluation):
+    global remove_not_rules
+    cc = True
+    while cc:
+        pred, cc = pred.apply_rules(remove_not_rules, evaluation)
+        debug_logical_expr("->  ", pred, evaluation)
+        if pred.is_true() or pred == SymbolFalse:
+            return pred
+    return pred
+
+
+def get_assumptions_list(evaluation):
     assumptions = None
     assumptions_def = evaluation.definitions.get_definition(
         "System`$Assumptions", only_if_exists=True
@@ -35,23 +133,254 @@ def get_assumptions_list(evaluation):
     return assumptions
 
 
+def remove_duplicated_assumptions(assumptions_list, evaluation):
+    if len(assumptions_list) == 0:
+        return assumptions_list
+    assumptions_list = sorted(assumptions_list)
+    unique_assumptions = [assumptions_list[0]]
+    for i, assumption in enumerate(assumptions_list):
+        if not (assumption == unique_assumptions[-1]):
+            unique_assumptions.append(assumption)
+    return unique_assumptions
 
-def evaluate_predicate(pred, evaluation):
-    if pred.has_form(("List", "Sequence"), None):
-        return Expression(pred._head,  *[evaluate_predicate(subp, evaluation) for subp in pred._leaves]  )
-    assumptions = get_assumptions_list(evaluation)
 
+def logical_expand_assumptions(assumptions_list, evaluation):
+    new_assumptions_list = []
+    changed = False
+    for assumption in assumptions_list:
+        if assumption.is_symbol():
+            if assumption.is_true():
+                changed = True
+                continue
+            if assumption == SymbolFalse:
+                evaluation.message("Assumption", "faas")
+                changed = True
+                continue
+            if assumption.is_numeric():
+                evaluation.message("Assumption", "baas")
+                changed = True
+                continue
+            new_assumptions_list.append(assumption)
+            continue
+        if assumption.has_form("And", None):
+            changed = True
+            for leaf in assumption.leaves:
+                new_assumptions_list.append(leaf)
+            continue
+        if assumption.has_form("Not", 1):
+            sentence = assumption._leaves[0]
+            if sentence.has_form("Or", None):
+                changed = True
+                for leaf in sentence._leaves:
+                    new_assumptions_list.append(Expression("Not", leaf))
+                continue
+            if sentence.has_form("And", None):
+                leaves = (Expression("Not", leaf) for leaf in sentence._leaves)
+                new_assumptions_list.append(Expression("Or", *leaves))
+                continue
+            if sentence.has_form("Implies", 2):
+                changed = True
+                new_assumptions_list.append(sentence._leaves[0])
+                new_assumptions_list.append(Expression("Not", sentence._leaves[1]))
+        if assumption.has_form("Nor", None):
+            changed = True
+            for leaf in assumption.leaves:
+                new_assumptions_list.append(Expression("Not", leaf))
+            continue
+        else:
+            new_assumptions_list.append(assumption)
+
+    if changed:
+        new_assumptions_list = remove_duplicated_assumptions(
+            new_assumptions_list, evaluation
+        )
+
+    return new_assumptions_list, changed
+
+
+def algebraic_expand_assumptions(assumptions_list, evaluation):
+    global logical_algebraic_rules
+    ensure_logical_algebraic_rules()
+    new_assumptions_list = []
+    changed = False
+    # First apply standard rules of reduction.
+    # These rules are generated the first time that are used.
+    for assumption in assumptions_list:
+        assumption, applied = assumption.apply_rules(
+            logical_algebraic_rules, evaluation
+        )
+        changed = changed or applied
+        new_assumptions_list.append(assumption)
+    if changed:
+        return new_assumptions_list, changed
+    # If not changed, let's try with the next set of rules
+    for assumption in assumptions_list:
+        if assumption.has_form("Not", 1):
+            nas, local_change = algebraic_expand_assumptions(
+                [assumption._leaves[0]], evaluation
+            )
+            if local_change:
+                changed = local_change
+                for na in nas:
+                    if na.has_form("Not", 1):
+                        new_assumptions_list.append(na._leaves[0])
+                    else:
+                        new_assumptions_list.append(Expression("Not", na))
+            else:
+                new_assumptions_list.append(assumption)
+        elif assumption.has_form(("Equal", "Unequal", "Equivalent"), (3, None)):
+            leaves = assumption.leaves()
+            head = assumption.get_head()
+            changed = True
+            for i in range(len(leaves)):
+                for j in range(i):
+                    new_assumptions_list.append(Expression(head, leaves[i], leaves[j]))
+                    new_assumptions_list.append(Expression(head, leaves[j], leaves[i]))
+        elif assumption.has_form(
+            ("Less", "Greater", "LessEqual", "GreaterEqual"), (3, None)
+        ):
+            leaves = assumption.leaves()
+            head = assumption.get_head()
+            changed = True
+            for i in range(len(leaves)):
+                for j in range(i):
+                    new_assumptions_list.append(Expression(head, leaves[i], leaves[j]))
+        else:
+            new_assumptions_list.append(assumption)
+
+    if changed:
+        assumptions_list = remove_duplicated_assumptions(
+            new_assumptions_list, evaluation
+        )
+        new_assumptions_list = []
+        for assumption in assumptions_list:
+            assumption, applied = assumption.apply_rules(
+                logical_algebraic_rules, evaluation
+            )
+            new_assumptions_list.append(assumption)
+    return new_assumptions_list, changed
+
+
+def get_assumption_rules_dispatch(evaluation):
+    # TODO: cache the generated rules...
+    assumptions_list = get_assumptions_list(evaluation)
+    if assumptions_list is None:
+        return None
+
+    # check for consistency:
+    consistent_assumptions = Expression("And", *assumptions_list)
+    val_consistent_assumptions = consistent_assumptions.evaluate(evaluation)
+    if val_consistent_assumptions == SymbolFalse:
+        evaluation.message("Inconsistent assumptions")
+
+    if assumptions_list is None:
+        return remove_nots_when_unnecesary(pred, evaluation).evaluate(evaluation)
+
+    # Expands Logically
+    assumptions_list, cont = logical_expand_assumptions(assumptions_list, evaluation)
+    while cont:
+        assumptions_list, cont = logical_expand_assumptions(
+            assumptions_list, evaluation
+        )
+
+    # Expands algebraically
+    assumptions_list, cont = algebraic_expand_assumptions(assumptions_list, evaluation)
+    while cont:
+        assumptions_list, cont = algebraic_expand_assumptions(
+            assumptions_list, evaluation
+        )
     assumption_rules = []
-    for assumption in assumptions:
-        true_state = True
-        while assumption.has_form("Not",1):
-            true_state = False
-            assumption = assumption._leaves[0]
-        if true_state:
-            assumption_rules.append(Rule(assumption, SymbolTrue))
+    for pat in assumptions_list:
+        value = True
+        while pat.has_form("Not", 1):
+            value = not value
+            pat = pat._leaves[0]
+
+        if value:
+            symbol_value = SymbolTrue
+            symbol_negate_value = SymbolFalse
+        else:
+            symbol_value = SymbolFalse
+            symbol_negate_value = SymbolTrue
+
+        if pat.has_form("Equal", 2):
+            if value:
+                lhs, rhs = pat._leaves
+                if lhs.is_numeric():
+                    assumption_rules.append(Rule(rhs, lhs))
+                else:
+                    assumption_rules.append(Rule(lhs, rhs))
+            else:
+                assumption_rules.append(Rule(pat, SymbolFalse))
+                symm_pat = Expression(pat._head, pat._leaves[1], pat._leaves[0])
+                assumption_rules.append(Rule(symm_pat, SymbolFalse))
+        elif pat.has_form("Equivalent", 2):
+            assumption_rules.append(Rule(pat, symbol_value))
+            symm_pat = Expression(pat._head, pat._leaves[1], pat._leaves[0])
+            assumption_rules.append(Rule(symm_pat, symbol_value))
+        elif pat.has_form("Less", 2):
+            if value:
+                assumption_rules.append(Rule(pat, SymbolTrue))
+                assumption_rules.append(
+                    Rule(
+                        Expression(pat._head, pat._leaves[1], pat._leaves[0]),
+                        SymbolFalse,
+                    )
+                )
+                for head in ("Equal", "Equivalent"):
+                    assumption_rules.append(
+                        Rule(
+                            Expression(head, pat._leaves[0], pat._leaves[1]),
+                            SymbolFalse,
+                        )
+                    )
+                    assumption_rules.append(
+                        Rule(
+                            Expression(head, pat._leaves[1], pat._leaves[0]),
+                            SymbolFalse,
+                        )
+                    )
+            else:
+                assumption_rules.append(Rule(pat, SymbolFalse))
         else:
-            assumption_rules.append(Rule(assumption, SymbolFalse))
-    
-    pred, changed = pred.apply_rules(assumption_rules, evaluation)
+            assumption_rules.append(Rule(pat, symbol_value))
+    # TODO: expand the pred and assumptions into an standard,
+    # atomized form, and then apply the rules...
+    if len(assumption_rules) == 0:
+        return None
+    return assumption_rules
+
+
+def evaluate_predicate(pred, evaluation):
+    global logical_algebraic_rules
+    global remove_not_rules
+
+    if pred.has_form(("List", "Sequence"), None):
+        return Expression(
+            pred._head, *[evaluate_predicate(subp, evaluation) for subp in pred._leaves]
+        )
+
+    debug_logical_expr("reducing ", pred, evaluation)
+    ensure_logical_algebraic_rules()
     pred = pred.evaluate(evaluation)
+    debug_logical_expr("->  ", pred, evaluation)
+    cc = True
+    while cc:
+        pred, cc = pred.apply_rules(logical_algebraic_rules, evaluation)
+        debug_logical_expr("->  ", pred, evaluation)
+        if pred.is_true() or pred == SymbolFalse:
+            return pred
+
+    assumption_rules = get_assumption_rules_dispatch(evaluation)
+    if assumption_rules is None:
+        return remove_nots_when_unnecesary(pred, evaluation).evaluate(evaluation)
+
+    if assumption_rules is not None:
+        debug_logical_expr(" Now, using the assumptions over ", pred, evaluation)
+        changed = True
+        while changed:
+            pred, changed = pred.apply_rules(assumption_rules, evaluation)
+            debug_logical_expr(" -> ", pred, evaluation)
+
+    pred = remove_nots_when_unnecesary(pred, evaluation).evaluate(evaluation)
     return pred