]> www.ginac.de Git - ginac.git/blobdiff - ginac/ex.cpp
Use the new parser in the ex(const string&, lst&) ctor.
[ginac.git] / ginac / ex.cpp
index b35cd8c8903b1d5c66c7494e37b45341c7f6b71f..7becb3e172da764458a6a28251c1526e8beec511 100644 (file)
@@ -3,7 +3,7 @@
  *  Implementation of GiNaC's light-weight expression handles. */
 
 /*
- *  GiNaC Copyright (C) 1999-2001 Johannes Gutenberg University Mainz, Germany
+ *  GiNaC Copyright (C) 1999-2008 Johannes Gutenberg University Mainz, Germany
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -17,7 +17,7 @@
  *
  *  You should have received a copy of the GNU General Public License
  *  along with this program; if not, write to the Free Software
- *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  */
 
 #include <iostream>
 #include "mul.h"
 #include "ncmul.h"
 #include "numeric.h"
+#include "matrix.h"
 #include "power.h"
 #include "lst.h"
 #include "relational.h"
 #include "input_lexer.h"
-#include "debugmsg.h"
 #include "utils.h"
 
 namespace GiNaC {
 
 //////////
-// other ctors
+// other constructors
 //////////
 
 // none (all inlined)
@@ -49,21 +49,6 @@ namespace GiNaC {
 
 // public
        
-/** Efficiently swap the contents of two expressions. */
-void ex::swap(ex & other)
-{
-       debugmsg("ex swap",LOGLEVEL_MEMBER_FUNCTION);
-
-       GINAC_ASSERT(bp!=0);
-       GINAC_ASSERT(bp->flags & status_flags::dynallocated);
-       GINAC_ASSERT(other.bp!=0);
-       GINAC_ASSERT(other.bp->flags & status_flags::dynallocated);
-       
-       basic * tmpbp = bp;
-       bp = other.bp;
-       other.bp = tmpbp;
-}
-
 /** Print expression to stream. The formatting of the output is determined
  *  by the kind of print_context object that is passed. Possible formattings
  *  include ginsh-parsable output (the default), tree-like output for
@@ -71,40 +56,25 @@ void ex::swap(ex & other)
  *  @see print_context */
 void ex::print(const print_context & c, unsigned level) const
 {
-       debugmsg("ex print", LOGLEVEL_PRINT);
-       GINAC_ASSERT(bp!=0);
        bp->print(c, level);
 }
 
-/** Print expression to stream in a tree-like format suitable for debugging. */
-void ex::printtree(std::ostream & os) const
-{
-       debugmsg("ex printtree", LOGLEVEL_PRINT);
-       GINAC_ASSERT(bp!=0);
-       bp->print(print_tree(os));
-}
-
 /** Little wrapper arount print to be called within a debugger. */
-void ex::dbgprint(void) const
+void ex::dbgprint() const
 {
-       debugmsg("ex dbgprint", LOGLEVEL_PRINT);
-       GINAC_ASSERT(bp!=0);
        bp->dbgprint();
 }
 
 /** Little wrapper arount printtree to be called within a debugger. */
-void ex::dbgprinttree(void) const
+void ex::dbgprinttree() const
 {
-       debugmsg("ex dbgprinttree", LOGLEVEL_PRINT);
-       GINAC_ASSERT(bp!=0);
        bp->dbgprinttree();
 }
 
 ex ex::expand(unsigned options) const
 {
-       GINAC_ASSERT(bp!=0);
        if (options == 0 && (bp->flags & status_flags::expanded)) // The "expanded" flag only covers the standard options; someone might want to re-expand with different options
-               return *bp;
+               return *this;
        else
                return bp->expand(options);
 }
@@ -116,8 +86,6 @@ ex ex::expand(unsigned options) const
  *  @return partial derivative as a new expression */
 ex ex::diff(const symbol & s, unsigned nth) const
 {
-       GINAC_ASSERT(bp!=0);
-
        if (!nth)
                return *this;
        else
@@ -127,7 +95,7 @@ ex ex::diff(const symbol & s, unsigned nth) const
 /** Check whether expression matches a specified pattern. */
 bool ex::match(const ex & pattern) const
 {
-       lst repl_lst;
+       exmap repl_lst;
        return bp->match(pattern, repl_lst);
 }
 
@@ -135,60 +103,165 @@ bool ex::match(const ex & pattern) const
  *  the "found" list. If the expression itself matches the pattern, the
  *  children are not further examined. This function returns true when any
  *  matches were found. */
-bool ex::find(const ex & pattern, lst & found) const
+bool ex::find(const ex & pattern, exset& found) const
 {
        if (match(pattern)) {
-               found.append(*this);
-               found.sort();
-               found.unique();
+               found.insert(*this);
                return true;
        }
        bool any_found = false;
-       for (unsigned i=0; i<nops(); i++)
+       for (size_t i=0; i<nops(); i++)
                if (op(i).find(pattern, found))
                        any_found = true;
        return any_found;
 }
 
-ex ex::operator[](const ex & index) const
+/** Substitute objects in an expression (syntactic substitution) and return
+ *  the result as a new expression. */
+ex ex::subs(const lst & ls, const lst & lr, unsigned options) const
 {
-       debugmsg("ex operator[ex]",LOGLEVEL_OPERATOR);
-       GINAC_ASSERT(bp!=0);
-       return (*bp)[index];
+       GINAC_ASSERT(ls.nops() == lr.nops());
+
+       // Convert the lists to a map
+       exmap m;
+       for (lst::const_iterator its = ls.begin(), itr = lr.begin(); its != ls.end(); ++its, ++itr) {
+               m.insert(std::make_pair(*its, *itr));
+
+               // Search for products and powers in the expressions to be substituted
+               // (for an optimization in expairseq::subs())
+               if (is_exactly_a<mul>(*its) || is_exactly_a<power>(*its))
+                       options |= subs_options::pattern_is_product;
+       }
+       if (!(options & subs_options::pattern_is_product))
+               options |= subs_options::pattern_is_not_product;
+
+       return bp->subs(m, options);
 }
 
-ex ex::operator[](int i) const
+/** Substitute objects in an expression (syntactic substitution) and return
+ *  the result as a new expression.  There are two valid types of
+ *  replacement arguments: 1) a relational like object==ex and 2) a list of
+ *  relationals lst(object1==ex1,object2==ex2,...). */
+ex ex::subs(const ex & e, unsigned options) const
 {
-       debugmsg("ex operator[int]",LOGLEVEL_OPERATOR);
-       GINAC_ASSERT(bp!=0);
-       return (*bp)[i];
+       if (e.info(info_flags::relation_equal)) {
+
+               // Argument is a relation: convert it to a map
+               exmap m;
+               const ex & s = e.op(0);
+               m.insert(std::make_pair(s, e.op(1)));
+
+               if (is_exactly_a<mul>(s) || is_exactly_a<power>(s))
+                       options |= subs_options::pattern_is_product;
+               else
+                       options |= subs_options::pattern_is_not_product;
+
+               return bp->subs(m, options);
+
+       } else if (e.info(info_flags::list)) {
+
+               // Argument is a list: convert it to a map
+               exmap m;
+               GINAC_ASSERT(is_a<lst>(e));
+               for (lst::const_iterator it = ex_to<lst>(e).begin(); it != ex_to<lst>(e).end(); ++it) {
+                       ex r = *it;
+                       if (!r.info(info_flags::relation_equal))
+                               throw(std::invalid_argument("basic::subs(ex): argument must be a list of equations"));
+                       const ex & s = r.op(0);
+                       m.insert(std::make_pair(s, r.op(1)));
+
+                       // Search for products and powers in the expressions to be substituted
+                       // (for an optimization in expairseq::subs())
+                       if (is_exactly_a<mul>(s) || is_exactly_a<power>(s))
+                               options |= subs_options::pattern_is_product;
+               }
+               if (!(options & subs_options::pattern_is_product))
+                       options |= subs_options::pattern_is_not_product;
+
+               return bp->subs(m, options);
+
+       } else
+               throw(std::invalid_argument("ex::subs(ex): argument must be a relation_equal or a list"));
+}
+
+/** Traverse expression tree with given visitor, preorder traversal. */
+void ex::traverse_preorder(visitor & v) const
+{
+       accept(v);
+
+       size_t n = nops();
+       for (size_t i = 0; i < n; ++i)
+               op(i).traverse_preorder(v);
+}
+
+/** Traverse expression tree with given visitor, postorder traversal. */
+void ex::traverse_postorder(visitor & v) const
+{
+       size_t n = nops();
+       for (size_t i = 0; i < n; ++i)
+               op(i).traverse_postorder(v);
+
+       accept(v);
 }
 
 /** Return modifyable operand/member at position i. */
-ex & ex::let_op(int i)
+ex & ex::let_op(size_t i)
 {
-       debugmsg("ex let_op()",LOGLEVEL_MEMBER_FUNCTION);
        makewriteable();
-       GINAC_ASSERT(bp!=0);
        return bp->let_op(i);
 }
 
+ex & ex::operator[](const ex & index)
+{
+       makewriteable();
+       return (*bp)[index];
+}
+
+ex & ex::operator[](size_t i)
+{
+       makewriteable();
+       return (*bp)[i];
+}
+
 /** Left hand side of relational expression. */
-ex ex::lhs(void) const
+ex ex::lhs() const
 {
-       debugmsg("ex lhs()",LOGLEVEL_MEMBER_FUNCTION);
-       if (!is_ex_of_type(*this,relational))
+       if (!is_a<relational>(*this))
                throw std::runtime_error("ex::lhs(): not a relation");
-       return (*static_cast<relational *>(bp)).lhs();
+       return bp->op(0);
 }
 
 /** Right hand side of relational expression. */
-ex ex::rhs(void) const
+ex ex::rhs() const
 {
-       debugmsg("ex rhs()",LOGLEVEL_MEMBER_FUNCTION);
-       if (!is_ex_of_type(*this,relational))
+       if (!is_a<relational>(*this))
                throw std::runtime_error("ex::rhs(): not a relation");
-       return (*static_cast<relational *>(bp)).rhs();
+       return bp->op(1);
+}
+
+/** Check whether expression is a polynomial. */
+bool ex::is_polynomial(const ex & vars) const
+{
+       if (is_a<lst>(vars)) {
+               const lst & varlst = ex_to<lst>(vars);
+               for (lst::const_iterator i=varlst.begin(); i!=varlst.end(); ++i)
+                       if (!bp->is_polynomial(*i))
+                               return false;
+               return true;
+       }
+       else
+               return bp->is_polynomial(vars);
+}
+
+/** Check whether expression is zero or zero matrix. */
+bool ex::is_zero_matrix() const
+{
+       if (is_zero())
+               return  true;
+       else {
+               ex e = evalm();
+               return is_a<matrix>(e) && ex_to<matrix>(e).is_zero_matrix();
+       }
 }
 
 // private
@@ -197,422 +270,289 @@ ex ex::rhs(void) const
  *  unlinking the object and creating an unshared copy of it. */
 void ex::makewriteable()
 {
-       debugmsg("ex makewriteable",LOGLEVEL_MEMBER_FUNCTION);
-       GINAC_ASSERT(bp!=0);
        GINAC_ASSERT(bp->flags & status_flags::dynallocated);
-       if (bp->refcount > 1) {
-               basic * bp2 = bp->duplicate();
-               ++bp2->refcount;
-               bp2->setflag(status_flags::dynallocated);
-               --bp->refcount;
-               bp = bp2;
-       }
-       GINAC_ASSERT(bp->refcount==1);
+       bp.makewritable();
+       GINAC_ASSERT(bp->get_refcount() == 1);
+}
+
+/** Share equal objects between expressions.
+ *  @see ex::compare(const ex &) */
+void ex::share(const ex & other) const
+{
+       if ((bp->flags | other.bp->flags) & status_flags::not_shareable)
+               return;
+
+       if (bp->get_refcount() <= other.bp->get_refcount())
+               bp = other.bp;
+       else
+               other.bp = bp;
 }
 
-/** Ctor from basic implementation.
+/** Helper function for the ex-from-basic constructor. This is where GiNaC's
+ *  automatic evaluator and memory management are implemented.
  *  @see ex::ex(const basic &) */
-void ex::construct_from_basic(const basic & other)
+ptr<basic> ex::construct_from_basic(const basic & other)
 {
        if (!(other.flags & status_flags::evaluated)) {
-               const ex & tmpex = other.eval(1); // evaluate only one (top) level
-               bp = tmpex.bp;
-               GINAC_ASSERT(bp->flags & status_flags::dynallocated);
-               ++bp->refcount;
-               if ((other.refcount==0) && (other.flags & status_flags::dynallocated))
-                       delete &const_cast<basic &>(other);
+
+               // The object is not yet evaluated, so call eval() to evaluate
+               // the top level. This will return either
+               //  a) the original object with status_flags::evaluated set (when the
+               //     eval() implementation calls hold())
+               // or
+               //  b) a different expression.
+               //
+               // eval() returns an ex, not a basic&, so this will go through
+               // construct_from_basic() a second time. In case a) we end up in
+               // the "else" branch below. In case b) we end up here again and
+               // apply eval() once more. The recursion stops when eval() calls
+               // hold() or returns an object that already has its "evaluated"
+               // flag set, such as a symbol or a numeric.
+               const ex & tmpex = other.eval(1);
+
+               // Eventually, the eval() recursion goes through the "else" branch
+               // below, which assures that the object pointed to by tmpex.bp is
+               // allocated on the heap (either it was already on the heap or it
+               // is a heap-allocated duplicate of another object).
+               GINAC_ASSERT(tmpex.bp->flags & status_flags::dynallocated); 
+
+               // If the original object is not referenced but heap-allocated,
+               // it means that eval() hit case b) above. The original object is
+               // no longer needed (it evaluated into something different), so we
+               // delete it (because nobody else will).
+               if ((other.get_refcount() == 0) && (other.flags & status_flags::dynallocated))
+                       delete &other; // yes, you can apply delete to a const pointer
+
+               // We can't return a basic& here because the tmpex is destroyed as
+               // soon as we leave the function, which would deallocate the
+               // evaluated object.
+               return tmpex.bp;
+
        } else {
+
+               // The easy case: making an "ex" out of an evaluated object.
                if (other.flags & status_flags::dynallocated) {
-                       // ok, it is already on the heap, so just copy bp:
-                       bp = &const_cast<basic &>(other);
+
+                       // The object is already heap-allocated, so we can just make
+                       // another reference to it.
+                       return ptr<basic>(const_cast<basic &>(other));
+
                } else {
-                       // create a duplicate on the heap:
-                       bp = other.duplicate();
+
+                       // The object is not heap-allocated, so we create a duplicate
+                       // on the heap.
+                       basic *bp = other.duplicate();
                        bp->setflag(status_flags::dynallocated);
+                       GINAC_ASSERT(bp->get_refcount() == 0);
+                       return bp;
                }
-               GINAC_ASSERT(bp!=0);
-               ++bp->refcount;
        }
-       GINAC_ASSERT(bp!=0);
-       GINAC_ASSERT(bp->flags & status_flags::dynallocated);
 }
 
-void ex::construct_from_int(int i)
+basic & ex::construct_from_int(int i)
 {
        switch (i) {  // prefer flyweights over new objects
        case -12:
-               bp = (basic*)_num_12_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_12_p);
        case -11:
-               bp = (basic*)_num_11_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_11_p);
        case -10:
-               bp = (basic*)_num_10_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_10_p);
        case -9:
-               bp = (basic*)_num_9_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_9_p);
        case -8:
-               bp = (basic*)_num_8_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_8_p);
        case -7:
-               bp = (basic*)_num_7_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_7_p);
        case -6:
-               bp = (basic*)_num_6_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_6_p);
        case -5:
-               bp = (basic*)_num_5_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_5_p);
        case -4:
-               bp = (basic*)_num_4_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_4_p);
        case -3:
-               bp = (basic*)_num_3_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_3_p);
        case -2:
-               bp = (basic*)_num_2_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_2_p);
        case -1:
-               bp = (basic*)_num_1_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_1_p);
        case 0:
-               bp = (basic*)_num0_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num0_p);
        case 1:
-               bp = (basic*)_num1_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num1_p);
        case 2:
-               bp = (basic*)_num2_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num2_p);
        case 3:
-               bp = (basic*)_num3_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num3_p);
        case 4:
-               bp = (basic*)_num4_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num4_p);
        case 5:
-               bp = (basic*)_num5_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num5_p);
        case 6:
-               bp = (basic*)_num6_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num6_p);
        case 7:
-               bp = (basic*)_num7_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num7_p);
        case 8:
-               bp = (basic*)_num8_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num8_p);
        case 9:
-               bp = (basic*)_num9_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num9_p);
        case 10:
-               bp = (basic*)_num10_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num10_p);
        case 11:
-               bp = (basic*)_num11_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num11_p);
        case 12:
-               bp = (basic*)_num12_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num12_p);
        default:
-               bp = new numeric(i);
+               basic *bp = new numeric(i);
                bp->setflag(status_flags::dynallocated);
-               ++bp->refcount;
-               GINAC_ASSERT((bp->flags) & status_flags::dynallocated);
-               GINAC_ASSERT(bp->refcount==1);
+               GINAC_ASSERT(bp->get_refcount() == 0);
+               return *bp;
        }
 }
        
-void ex::construct_from_uint(unsigned int i)
+basic & ex::construct_from_uint(unsigned int i)
 {
        switch (i) {  // prefer flyweights over new objects
        case 0:
-               bp = (basic*)_num0_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num0_p);
        case 1:
-               bp = (basic*)_num1_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num1_p);
        case 2:
-               bp = (basic*)_num2_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num2_p);
        case 3:
-               bp = (basic*)_num3_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num3_p);
        case 4:
-               bp = (basic*)_num4_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num4_p);
        case 5:
-               bp = (basic*)_num5_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num5_p);
        case 6:
-               bp = (basic*)_num6_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num6_p);
        case 7:
-               bp = (basic*)_num7_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num7_p);
        case 8:
-               bp = (basic*)_num8_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num8_p);
        case 9:
-               bp = (basic*)_num9_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num9_p);
        case 10:
-               bp = (basic*)_num10_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num10_p);
        case 11:
-               bp = (basic*)_num11_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num11_p);
        case 12:
-               bp = (basic*)_num12_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num12_p);
        default:
-               bp = new numeric(i);
+               basic *bp = new numeric(i);
                bp->setflag(status_flags::dynallocated);
-               ++bp->refcount;
-               GINAC_ASSERT((bp->flags) & status_flags::dynallocated);
-               GINAC_ASSERT(bp->refcount==1);
+               GINAC_ASSERT(bp->get_refcount() == 0);
+               return *bp;
        }
 }
        
-void ex::construct_from_long(long i)
+basic & ex::construct_from_long(long i)
 {
        switch (i) {  // prefer flyweights over new objects
        case -12:
-               bp = (basic*)_num_12_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_12_p);
        case -11:
-               bp = (basic*)_num_11_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_11_p);
        case -10:
-               bp = (basic*)_num_10_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_10_p);
        case -9:
-               bp = (basic*)_num_9_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_9_p);
        case -8:
-               bp = (basic*)_num_8_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_8_p);
        case -7:
-               bp = (basic*)_num_7_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_7_p);
        case -6:
-               bp = (basic*)_num_6_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_6_p);
        case -5:
-               bp = (basic*)_num_5_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_5_p);
        case -4:
-               bp = (basic*)_num_4_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_4_p);
        case -3:
-               bp = (basic*)_num_3_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_3_p);
        case -2:
-               bp = (basic*)_num_2_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_2_p);
        case -1:
-               bp = (basic*)_num_1_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num_1_p);
        case 0:
-               bp = (basic*)_num0_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num0_p);
        case 1:
-               bp = (basic*)_num1_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num1_p);
        case 2:
-               bp = (basic*)_num2_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num2_p);
        case 3:
-               bp = (basic*)_num3_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num3_p);
        case 4:
-               bp = (basic*)_num4_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num4_p);
        case 5:
-               bp = (basic*)_num5_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num5_p);
        case 6:
-               bp = (basic*)_num6_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num6_p);
        case 7:
-               bp = (basic*)_num7_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num7_p);
        case 8:
-               bp = (basic*)_num8_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num8_p);
        case 9:
-               bp = (basic*)_num9_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num9_p);
        case 10:
-               bp = (basic*)_num10_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num10_p);
        case 11:
-               bp = (basic*)_num11_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num11_p);
        case 12:
-               bp = (basic*)_num12_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num12_p);
        default:
-               bp = new numeric(i);
+               basic *bp = new numeric(i);
                bp->setflag(status_flags::dynallocated);
-               ++bp->refcount;
-               GINAC_ASSERT((bp->flags) & status_flags::dynallocated);
-               GINAC_ASSERT(bp->refcount==1);
+               GINAC_ASSERT(bp->get_refcount() == 0);
+               return *bp;
        }
 }
        
-void ex::construct_from_ulong(unsigned long i)
+basic & ex::construct_from_ulong(unsigned long i)
 {
        switch (i) {  // prefer flyweights over new objects
        case 0:
-               bp = (basic*)_num0_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num0_p);
        case 1:
-               bp = (basic*)_num1_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num1_p);
        case 2:
-               bp = (basic*)_num2_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num2_p);
        case 3:
-               bp = (basic*)_num3_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num3_p);
        case 4:
-               bp = (basic*)_num4_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num4_p);
        case 5:
-               bp = (basic*)_num5_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num5_p);
        case 6:
-               bp = (basic*)_num6_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num6_p);
        case 7:
-               bp = (basic*)_num7_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num7_p);
        case 8:
-               bp = (basic*)_num8_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num8_p);
        case 9:
-               bp = (basic*)_num9_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num9_p);
        case 10:
-               bp = (basic*)_num10_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num10_p);
        case 11:
-               bp = (basic*)_num11_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num11_p);
        case 12:
-               bp = (basic*)_num12_p;
-               ++bp->refcount;
-               break;
+               return *const_cast<numeric *>(_num12_p);
        default:
-               bp = new numeric(i);
+               basic *bp = new numeric(i);
                bp->setflag(status_flags::dynallocated);
-               ++bp->refcount;
-               GINAC_ASSERT((bp->flags) & status_flags::dynallocated);
-               GINAC_ASSERT(bp->refcount==1);
+               GINAC_ASSERT(bp->get_refcount() == 0);
+               return *bp;
        }
 }
        
-void ex::construct_from_double(double d)
+basic & ex::construct_from_double(double d)
 {
-       bp = new numeric(d);
+       basic *bp = new numeric(d);
        bp->setflag(status_flags::dynallocated);
-       ++bp->refcount;
-       GINAC_ASSERT((bp->flags) & status_flags::dynallocated);
-       GINAC_ASSERT(bp->refcount==1);
+       GINAC_ASSERT(bp->get_refcount() == 0);
+       return *bp;
 }
 
-void ex::construct_from_string_and_lst(const std::string &s, const ex &l)
-{
-       set_lexer_string(s);
-       set_lexer_symbols(l);
-       ginac_yyrestart(NULL);
-       if (ginac_yyparse())
-               throw (std::runtime_error(get_parser_error()));
-       else {
-               bp = parsed_ex.bp;
-               GINAC_ASSERT(bp!=0);
-               GINAC_ASSERT((bp->flags) & status_flags::dynallocated);
-               ++bp->refcount;
-       }
-}
-       
 //////////
 // static member variables
 //////////