simplify nex_creator

Signed-off-by: Lev Nachmanson <levnach@hotmail.com>

src/math/lp/nex.h

@@ -191,6 +191,21 @@ public:
     void add_child(nex* e) {
         add_child_in_power(e, 1);
     }
+
+    // returns true if the product of scalars gives a number different from 1
+    bool has_a_coeff() const {
+        rational r(1);
+        for (auto & p : *this) {
+            if (p.e()->is_scalar())
+                r *= to_scalar(p.e())->value();
+        }
+        return !r.is_one();
+    }
+
+    const nex_pow* begin() const { return m_children.begin(); }
+    const nex_pow* end() const { return m_children.end(); }
+    nex_pow* begin() { return m_children.begin(); }
+    nex_pow* end() { return m_children.end(); }
     
     void add_child_in_power(nex* e, int power) { m_children.push_back(nex_pow(e, power)); }
 

src/math/lp/nex_creator.cpp

@@ -379,14 +379,14 @@ nex* nex_creator::create_child_from_nex_and_coeff(nex *e,
     }        
     case expr_type::MUL: {
         nex_mul * em = to_mul(e);
-        nex_pow *np = em->children().begin();
+        nex_pow *np = em->begin();
         if (np->e()->is_scalar()) {
             SASSERT(np->pow() == 1);
             to_scalar(np->e())->value() = coeff;
             return e;
         }
         em->add_child(mk_scalar(coeff));
-        std::sort(em->children().begin(), em->children().end(), [this](const nex_pow& a,
+        std::sort(em->begin(), em->end(), [this](const nex_pow& a,
                                                                        const nex_pow& b) {return less_than_on_nex_pow(a, b);});
         return em;
     }
@@ -415,11 +415,11 @@ bool nex_creator::register_in_join_map(std::map<nex*, rational, nex_lt>& map, ne
 // returns true if a simplificatian happens
 bool nex_creator::process_mul_in_simplify_sum(nex_mul* em, std::map<nex*, rational, nex_lt> &map) {
     bool found = false;
-    auto it = em->children().begin();
+    auto it = em->begin();
     if (it->e()->is_scalar()) {
         SASSERT(it->pow() == 1);
         rational r = to_scalar(it->e())->value();              
-        auto end = em->children().end();
+        auto end = em->end();
         if (em->children().size() == 2 && em->children()[1].pow() == 1) {
             found = register_in_join_map(map, em->children()[1].e(), r);
         } else {
@@ -536,20 +536,21 @@ bool have_no_scalars(const nex_mul* a) {
     return true;
 }
 
+nex * nex_creator::mk_div_sum_by_mul(const nex_sum* m, const nex_mul* b) {
+    nex_sum * r = mk_sum();
+    for (auto e : m->children()) {
+        r->add_child(mk_div_by_mul(e, b));
+    }
+    TRACE("nla_cn_details", tout << *r << "\n";);
+    return r;
+}
 
 nex * nex_creator::mk_div_by_mul(const nex* a, const nex_mul* b) {
-
-    // todo: break on shorter funcitons
     if (a->is_sum()) {
-        nex_sum * r = mk_sum();
+        return mk_div_sum_by_mul(to_sum(a), b);
-        const nex_sum * m = to_sum(a);
-        for (auto e : m->children()) {
-            r->add_child(mk_div_by_mul(e, b));
-        }
-        TRACE("nla_cn_details", tout << *r << "\n";);
-        return r;
     }
     if (a->is_var() || (a->is_mul() && to_mul(a)->children().size() == 1)) {
+        SASSERT(b->get_degree() == 1 && !b->has_a_coeff() && b->contains(to_var(a)->var()));        
         return mk_scalar(rational(1));
     }
     const nex_mul* am = to_mul(a);

src/math/lp/nex_creator.h

@@ -203,6 +203,7 @@ public:
     nex * mk_div(const nex* a, lpvar j);
     nex * mk_div(const nex* a, const nex* b);
     nex * mk_div_by_mul(const nex* a, const nex_mul* b);
+    nex * mk_div_sum_by_mul(const nex_sum* a, const nex_mul* b);
     
     nex * simplify_mul(nex_mul *e);    
     bool is_sorted(const nex_mul * e) const;    
@@ -236,6 +237,6 @@ public:
     bool less_than_on_var_nex(const nex_var* a, const nex* b) const;
     bool less_than_on_mul_nex(const nex_mul* a, const nex* b) const;
     void fill_map_with_children(std::map<nex*, rational, nex_lt> & m, ptr_vector<nex> & children);
-    void process_map_pair(nex *e, const rational& coeff, ptr_vector<nex> & children, std::unordered_set<nex*>&);   
+    void process_map_pair(nex *e, const rational& coeff, ptr_vector<nex> & children, std::unordered_set<nex*>&);
 };
 }