WIP: keyword arguments for expressions

src/ant/ant/antObject.cc

@@ -431,7 +431,7 @@ public:
     // .. nothing yet ..
   }
 
-  void execute (const tl::ExpressionParserContext &context, tl::Variant &out, const std::vector <tl::Variant> &vv) const
+  void execute (const tl::ExpressionParserContext &context, tl::Variant &out, const std::vector <tl::Variant> &vv, const std::map<std::string, tl::Variant> * /*kwargs*/) const
   {
     if (vv.size () != 0) {
       throw tl::EvalError (tl::to_string (tr ("Annotation function must not have arguments")), context);

src/db/db/dbLayoutQuery.cc

@@ -2194,7 +2194,7 @@ public:
     //  .. nothing yet ..
   }
 
-  void execute (const tl::ExpressionParserContext &context, tl::Variant &out, const std::vector<tl::Variant> &args) const 
+  void execute (const tl::ExpressionParserContext &context, tl::Variant &out, const std::vector<tl::Variant> &args, const std::map<std::string, tl::Variant> * /*kwargs*/) const
   {
     if (args.size () > 0) {
       throw tl::EvalError (tl::to_string (tr ("Query function does not allow parameters")), context);

src/db/db/dbLoadLayoutOptions.cc

@@ -133,7 +133,7 @@ namespace db
         args.push_back (value);
       }
       tl::ExpressionParserContext context;
-      ref.user_cls ()->eval_cls ()->execute (context, out, ref, m, args);
+      ref.user_cls ()->eval_cls ()->execute (context, out, ref, m, args, 0);
 
       ref = out;
 
@@ -160,7 +160,7 @@ namespace db
 
       std::vector<tl::Variant> args;
       tl::ExpressionParserContext context;
-      ref.user_cls ()->eval_cls ()->execute (context, out, ref, m, args);
+      ref.user_cls ()->eval_cls ()->execute (context, out, ref, m, args, 0);
 
       ref = out;
 

src/db/db/dbSaveLayoutOptions.cc

@@ -138,7 +138,7 @@ SaveLayoutOptions::set_option_by_name (const std::string &method, const tl::Vari
   tl::Variant out;
   std::vector<tl::Variant> args;
   args.push_back (value);
-  eval_cls->execute (context, out, options_ref, method + "=", args);
+  eval_cls->execute (context, out, options_ref, method + "=", args, 0);
 }
 
 tl::Variant
@@ -151,7 +151,7 @@ SaveLayoutOptions::get_option_by_name (const std::string &method)
 
   tl::Variant out;
   std::vector<tl::Variant> args;
-  eval_cls->execute (context, out, options_ref, method, args);
+  eval_cls->execute (context, out, options_ref, method, args, 0);
 
   return out;
 }

src/db/db/dbTilingProcessor.cc

@@ -487,7 +487,7 @@ public:
     //  .. nothing yet ..
   }
 
-  void execute (const tl::ExpressionParserContext & /*context*/, tl::Variant &out, const std::vector<tl::Variant> &args) const
+  void execute (const tl::ExpressionParserContext & /*context*/, tl::Variant &out, const std::vector<tl::Variant> &args, const std::map<std::string, tl::Variant> * /*kwargs*/) const
   {
     out = mp_proc->receiver (args);
   }
@@ -506,7 +506,7 @@ public:
     //  .. nothing yet ..
   }
 
-  void execute (const tl::ExpressionParserContext & /*context*/, tl::Variant & /*out*/, const std::vector<tl::Variant> &args) const 
+  void execute (const tl::ExpressionParserContext & /*context*/, tl::Variant & /*out*/, const std::vector<tl::Variant> &args, const std::map<std::string, tl::Variant> * /*kwargs*/) const
   {
     mp_proc->put (m_ix, m_iy, m_tile_box, args);
   }
@@ -526,7 +526,7 @@ public:
     //  .. nothing yet ..
   }
 
-  void execute (const tl::ExpressionParserContext & /*context*/, tl::Variant & /*out*/, const std::vector<tl::Variant> & /*args*/) const 
+  void execute (const tl::ExpressionParserContext & /*context*/, tl::Variant & /*out*/, const std::vector<tl::Variant> & /*args*/, const std::map<std::string, tl::Variant> * /*kwargs*/) const
   {
     // TODO: ... implement ..
   }

src/gsi/gsi/gsiClass.h

@@ -84,7 +84,7 @@ template<class T, bool> struct _var_user_to_string_impl;
 template<class T>
 struct _var_user_to_string_impl<T, true>
 {
-  static std::string call (const T *a, const VariantUserClassImpl * /*delegate*/) { return a->to_string (); }
+  static std::string call (const T *a, const VariantUserClassImpl * /*delegate*/) { return a ? a->to_string () : std::string (); }
 };
 
 template<class T>

src/gsi/gsi/gsiExpression.cc

@@ -266,9 +266,15 @@ public:
     //  .. nothing yet ..
   }
 
-  void execute (const tl::ExpressionParserContext & /*context*/, tl::Variant &out, const std::vector<tl::Variant> &args) const 
+  bool supports_keyword_parameters () const
   {
-    if (! args.empty ()) {
+    //  for future extensions
+    return true;
+  }
+
+  void execute (const tl::ExpressionParserContext & /*context*/, tl::Variant &out, const std::vector<tl::Variant> &args, const std::map<std::string, tl::Variant> *kwargs) const
+  {
+    if (! args.empty () || kwargs) {
       throw tl::Exception (tl::to_string (tr ("Class '%s' is not a function - use 'new' to create a new object")), mp_var_cls->name ());
     }
     out = tl::Variant ((void *) 0, mp_var_cls, false);
@@ -532,12 +538,12 @@ VariantUserClassImpl::to_double_impl (void *obj) const
 }
 
 void
-VariantUserClassImpl::execute (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args) const
+VariantUserClassImpl::execute (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args, const std::map<std::string, tl::Variant> *kwargs) const
 {
   if (mp_object_cls == 0 && method == "is_a") {
 
-    if (args.size () != 1) {
-      throw tl::EvalError (tl::to_string (tr ("'is_a' method requires exactly one argument")), context);
+    if (args.size () != 1 || kwargs) {
+      throw tl::EvalError (tl::to_string (tr ("'is_a' method requires exactly one argument (no keyword arguments)")), context);
     }
 
     bool ret = false;
@@ -550,7 +556,7 @@ VariantUserClassImpl::execute (const tl::ExpressionParserContext &context, tl::V
 
     out = ret;
 
-  } else if (mp_object_cls != 0 && method == "new" && args.size () == 0) {
+  } else if (mp_object_cls != 0 && method == "new" && args.size () == 0 && ! kwargs) {
 
     void *obj = mp_cls->create ();
     if (obj) {
@@ -574,8 +580,8 @@ VariantUserClassImpl::execute (const tl::ExpressionParserContext &context, tl::V
 
   } else if (mp_object_cls == 0 && method == "dup") {
 
-    if (args.size () != 0) {
-      throw tl::EvalError (tl::to_string (tr ("'dup' method does not allow arguments")), context);
+    if (args.size () != 0 || kwargs) {
+      throw tl::EvalError (tl::to_string (tr ("'dup' method does not allow arguments (no keyword arguments)")), context);
     }
 
     void *obj = mp_cls->create ();
@@ -602,7 +608,7 @@ VariantUserClassImpl::execute (const tl::ExpressionParserContext &context, tl::V
 
   } else {
     try {
-      execute_gsi (context, out, object, method, args);
+      execute_gsi (context, out, object, method, args, kwargs);
     } catch (tl::EvalError &) {
       throw;
     } catch (tl::Exception &ex) {
@@ -709,8 +715,92 @@ static const gsi::ClassBase *find_class_scope (const gsi::ClassBase *cls, const
   return 0;
 }
 
+inline int
+num_args (const gsi::MethodBase *m)
+{
+  return int (m->end_arguments () - m->begin_arguments ());
+}
+
+static bool
+compatible_with_args (const gsi::MethodBase *m, int argc, const std::map<std::string, tl::Variant> *kwargs)
+{
+  int nargs = num_args (m);
+
+  if (argc >= nargs) {
+    //  no more arguments to consider
+    return argc == nargs && (! kwargs || kwargs->empty ());
+  }
+
+  if (kwargs) {
+
+    int nkwargs = int (kwargs->size ());
+    int kwargs_taken = 0;
+
+    while (argc < nargs) {
+      const gsi::ArgType &atype = m->begin_arguments () [argc];
+      auto i = kwargs->find (atype.spec ()->name ());
+      if (i == kwargs->end ()) {
+        if (! atype.spec ()->has_default ()) {
+          return false;
+        }
+      } else {
+        ++kwargs_taken;
+      }
+      ++argc;
+    }
+
+    //  matches if all keyword arguments are taken
+    return kwargs_taken == nkwargs;
+
+  } else {
+
+    while (argc < nargs) {
+      const gsi::ArgType &atype = m->begin_arguments () [argc];
+      if (! atype.spec ()->has_default ()) {
+        return false;
+      }
+      ++argc;
+    }
+
+    return true;
+
+  }
+}
+
+static std::string
+describe_overload (const gsi::MethodBase *m, int argc, const std::map<std::string, tl::Variant> *kwargs)
+{
+  std::string res = m->to_string ();
+  if (compatible_with_args (m, argc, kwargs)) {
+    res += " " + tl::to_string (tr ("[match candidate]"));
+  }
+  return res;
+}
+
+static std::string
+describe_overloads (const ExpressionMethodTable *mt, int mid, int argc, const std::map<std::string, tl::Variant> *kwargs)
+{
+  std::string res;
+  for (auto m = mt->begin (mid); m != mt->end (mid); ++m) {
+    res += std::string ("  ") + describe_overload (*m, argc, kwargs) + "\n";
+  }
+  return res;
+}
+
+static const tl::Variant *
+get_kwarg (const gsi::ArgType &atype, const std::map<std::string, tl::Variant> *kwargs)
+{
+  if (kwargs) {
+    auto i = kwargs->find (atype.spec ()->name ());
+    if (i != kwargs->end ()) {
+      return &i->second;
+    }
+  }
+  return 0;
+}
+
 void
-VariantUserClassImpl::execute_gsi (const tl::ExpressionParserContext & /*context*/, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args) const
+VariantUserClassImpl::execute_gsi (const tl::ExpressionParserContext & /*context*/, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args, const std::map<std::string, tl::Variant> *kwargs) const
 {
   tl_assert (object.is_user ());
 
@@ -762,7 +852,7 @@ VariantUserClassImpl::execute_gsi (const tl::ExpressionParserContext & /*context
       throw tl::Exception (tl::sprintf (tl::to_string (tr ("Signals are not supported inside expressions (event %s)")), method.c_str ()));
     } else if ((*m)->is_callback()) {
       //  ignore callbacks
-    } else if ((*m)->compatible_with_num_args ((unsigned int) args.size ())) {
+    } else if (compatible_with_args (*m, int (args.size ()), kwargs)) {
       ++candidates;
       meth = *m;
     }
@@ -771,20 +861,7 @@ VariantUserClassImpl::execute_gsi (const tl::ExpressionParserContext & /*context
 
   //  no candidate -> error
   if (! meth) {
-
-    std::set<unsigned int> nargs;
-    for (ExpressionMethodTableEntry::method_iterator m = mt->begin (mid); m != mt->end (mid); ++m) {
-      nargs.insert (std::distance ((*m)->begin_arguments (), (*m)->end_arguments ()));
-    }
-    std::string nargs_s;
-    for (std::set<unsigned int>::const_iterator na = nargs.begin (); na != nargs.end (); ++na) {
-      if (na != nargs.begin ()) {
-        nargs_s += "/";
-      }
-      nargs_s += tl::to_string (*na);
-    }
-
-    throw tl::Exception (tl::sprintf (tl::to_string (tr ("Invalid number of arguments for method %s, class %s (got %d, expected %s)")), method.c_str (), mp_cls->name (), int (args.size ()), nargs_s));
+    throw tl::Exception (tl::to_string (tr ("Can't match arguments. Variants are:\n")) + describe_overloads (mt, mid, int (args.size ()), kwargs));
   }
 
   //  more than one candidate -> refine by checking the arguments
@@ -800,13 +877,16 @@ VariantUserClassImpl::execute_gsi (const tl::ExpressionParserContext & /*context
       if (! (*m)->is_callback () && ! (*m)->is_signal ()) {
 
         //  check arguments (count and type)
-        bool is_valid = (*m)->compatible_with_num_args ((unsigned int) args.size ());
+        bool is_valid = compatible_with_args (*m, (int) args.size (), kwargs);
         int sc = 0;
         int i = 0;
-        for (gsi::MethodBase::argument_iterator a = (*m)->begin_arguments (); is_valid && i < int (args.size ()) && a != (*m)->end_arguments (); ++a, ++i) {
-          if (gsi::test_arg (*a, args [i], false /*strict*/)) {
+        for (gsi::MethodBase::argument_iterator a = (*m)->begin_arguments (); is_valid && a != (*m)->end_arguments (); ++a, ++i) {
+          const tl::Variant *arg = i >= int (args.size ()) ? get_kwarg (*a, kwargs) : &args[i];
+          if (! arg) {
+            is_valid = a->spec ()->has_default ();
+          } else if (gsi::test_arg (*a, *arg, false /*strict*/)) {
             ++sc;
-          } else if (test_arg (*a, args [i], true /*loose*/)) {
+          } else if (test_arg (*a, *arg, true /*loose*/)) {
             //  non-scoring match
           } else {
             is_valid = false;
@@ -831,12 +911,17 @@ VariantUserClassImpl::execute_gsi (const tl::ExpressionParserContext & /*context
 
         if (is_valid) {
 
-          //  otherwise take the candidate with the better score
-          if (candidates > 0 && sc > score) {
-            candidates = 1;
-            meth = *m;
-            score = sc;
-          } else if (candidates == 0 || sc == score) {
+          //  otherwise take the candidate with the better score or the least number of arguments (faster)
+          if (candidates > 0) {
+            if (sc > score || (sc == score && num_args (meth) > num_args (*m))) {
+              candidates = 1;
+              meth = *m;
+              score = sc;
+            } else if (sc == score && num_args (meth) == num_args (*m)) {
+              ++candidates;
+              meth = *m;
+            }
+          } else {
             ++candidates;
             meth = *m;
             score = sc;
@@ -851,11 +936,11 @@ VariantUserClassImpl::execute_gsi (const tl::ExpressionParserContext & /*context
   }
 
   if (! meth) {
-    throw tl::Exception (tl::sprintf (tl::to_string (tr ("No method with matching arguments for method %s, class %s")), method.c_str (), mp_cls->name ()));
+    throw tl::Exception (tl::to_string (tr ("No overload with matching arguments. Variants are:\n")) + describe_overloads (mt, mid, int (args.size ()), kwargs));
   }
 
   if (candidates > 1) {
-    throw tl::Exception (tl::sprintf (tl::to_string (tr ("Ambiguous overload variants for method %s, class %s - multiple method declarations match arguments")), method.c_str (), mp_cls->name ()));
+    throw tl::Exception (tl::to_string (tr ("Ambiguous overload variants - multiple method declarations match arguments. Variants are:\n")) + describe_overloads (mt, mid, int (args.size ()), kwargs));
   }
 
   if (m_is_const && ! meth->is_const ()) {
@@ -869,22 +954,76 @@ VariantUserClassImpl::execute_gsi (const tl::ExpressionParserContext & /*context
 
   } else if (meth->smt () != gsi::MethodBase::None) {
 
+    if (kwargs) {
+      throw tl::Exception (tl::to_string (tr ("Keyword arguments not permitted")));
+    }
+
     out = special_method_impl (meth->smt (), object, args);
 
   } else {
 
     gsi::SerialArgs arglist (meth->argsize ());
     tl::Heap heap;
-    size_t narg = 0;
-    for (gsi::MethodBase::argument_iterator a = meth->begin_arguments (); a != meth->end_arguments () && narg < args.size (); ++a, ++narg) {
+
+    int iarg = 0;
+    int kwargs_taken = 0;
+    int nkwargs = kwargs ? int (kwargs->size ()) : 0;
+
+    for (gsi::MethodBase::argument_iterator a = meth->begin_arguments (); a != meth->end_arguments (); ++a, ++iarg) {
+
       try {
-        //  Note: this const_cast is ugly, but it will basically enable "out" parameters
-        //  TODO: clean this up.
-        gsi::push_arg (arglist, *a, const_cast<tl::Variant &> (args [narg]), &heap);
+
+        const tl::Variant *arg = iarg >= int (args.size ()) ? get_kwarg (*a, kwargs) : &args[iarg];
+        if (! arg) {
+          if (a->spec ()->has_default ()) {
+            if (kwargs_taken == nkwargs) {
+              //  leave it to the consumer to establish the default values (that is faster)
+              break;
+            }
+            tl::Variant def_value = a->spec ()->default_value ();
+            gsi::push_arg (arglist, *a, def_value, &heap);
+          } else {
+            throw tl::Exception (tl::to_string ("No argument provided (positional or keyword) and no default value available"));
+          }
+        } else {
+          if (iarg >= int (args.size ())) {
+            ++kwargs_taken;
+          }
+          //  Note: this const_cast is ugly, but it will basically enable "out" parameters
+          //  TODO: clean this up.
+          gsi::push_arg (arglist, *a, const_cast<tl::Variant &> (*arg), &heap);
+        }
+
       } catch (tl::Exception &ex) {
         std::string msg = ex.msg () + tl::sprintf (tl::to_string (tr (" (argument '%s')")), a->spec ()->name ());
         throw tl::Exception (msg);
       }
+
+    }
+
+    if (kwargs_taken != nkwargs) {
+
+      //  check if there are any left-over keyword parameters with unknown names
+
+      std::set<std::string> valid_names;
+      for (gsi::MethodBase::argument_iterator a = meth->begin_arguments (); a != meth->end_arguments (); ++a) {
+        valid_names.insert (a->spec ()->name ());
+      }
+
+      std::set<std::string> invalid_names;
+      for (auto i = kwargs->begin (); i != kwargs->end (); ++i) {
+        if (valid_names.find (i->first) == valid_names.end ()) {
+          invalid_names.insert (i->first);
+        }
+      }
+
+      if (invalid_names.size () > 1) {
+        std::string names_str = tl::join (invalid_names.begin (), invalid_names.end (), ", ");
+        throw tl::Exception (tl::to_string (tr ("Unknown keyword parameters: ")) + names_str);
+      } else if (invalid_names.size () == 1) {
+        throw tl::Exception (tl::to_string (tr ("Unknown keyword parameter: ")) + *invalid_names.begin ());
+      }
+
     }
 
     SerialArgs retlist (meth->retsize ());

src/gsi/gsi/gsiExpression.h

@@ -55,7 +55,7 @@ public:
   int to_int_impl (void *) const;
   double to_double_impl (void *) const;
 
-  virtual void execute (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args) const;
+  virtual void execute (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args, const std::map<std::string, tl::Variant> *kwargs) const;
 
   void initialize (const gsi::ClassBase *cls, const tl::VariantUserClassBase *self, const tl::VariantUserClassBase *object_cls, bool is_const);
 
@@ -64,7 +64,7 @@ private:
   const tl::VariantUserClassBase *mp_self, *mp_object_cls;
   bool m_is_const;
 
-  virtual void execute_gsi (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args) const;
+  virtual void execute_gsi (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args, const std::map<std::string, tl::Variant> *kwargs = 0) const;
 
   bool has_method (const std::string &method) const;
 };

src/gsi/unit_tests/gsiExpressionTests.cc

@@ -564,7 +564,7 @@ class CollectFunction
   : public tl::EvalFunction
 {
 public:
-  virtual void execute (const tl::ExpressionParserContext & /*context*/, tl::Variant &out, const std::vector<tl::Variant> &args) const
+  virtual void execute (const tl::ExpressionParserContext & /*context*/, tl::Variant &out, const std::vector<tl::Variant> &args, const std::map<std::string, tl::Variant> * /*kwargs*/) const
   {
     out = tl::Variant ();
     if (args.size () > 0) {
@@ -623,3 +623,32 @@ TEST(11)
   v = e.parse ("var b = Trans.new(1)*Trans.new(Vector.new(10, 20))").execute ();
   EXPECT_EQ (v.to_string (), std::string ("r90 -20,10"));
 }
+
+TEST(12)
+{
+  //  Keyword arguments are best tested on transformations, here CplxTrans
+
+  tl::Eval e;
+  tl::Variant v;
+
+  v = e.parse ("var t = CplxTrans.new()").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("r0 *1 0,0"));
+  v = e.parse ("var t = CplxTrans.new(1.5)").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("r0 *1.5 0,0"));
+  v = e.parse ("var t = CplxTrans.new(1, 2)").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("r0 *1 1,2"));
+  v = e.parse ("var t = CplxTrans.new(1, y=2)").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("r0 *1 1,2"));
+  v = e.parse ("var t = CplxTrans.new(x=1, y=2)").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("r0 *1 1,2"));
+  v = e.parse ("var t = CplxTrans.new(u=DVector.new(1, 2))").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("r0 *1 1,2"));
+  v = e.parse ("var t = CplxTrans.new(DVector.new(1, 2))").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("r0 *1 1,2"));
+  v = e.parse ("var t = CplxTrans.new(u=Vector.new(1, 2))").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("r0 *1 1,2"));
+  v = e.parse ("var t = CplxTrans.new(u=[1, 2])").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("r0 *1 1,2"));
+  v = e.parse ("var t = CplxTrans.new(mag=1.5)").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("r0 *1.5 0,0"));
+}

src/laybasic/laybasic/layLayerProperties.cc

@@ -436,7 +436,7 @@ public:
     // .. nothing yet ..
   }
 
-  void execute (const tl::ExpressionParserContext &context, tl::Variant &out, const std::vector <tl::Variant> &vv) const
+  void execute (const tl::ExpressionParserContext &context, tl::Variant &out, const std::vector <tl::Variant> &vv, const std::map<std::string, tl::Variant> * /*kwargs*/) const
   {
     if (vv.size () != 0) {
       throw tl::EvalError (tl::to_string (tr ("Layer source function must not have arguments")), context);

src/rba/rba/rba.cc

@@ -531,11 +531,11 @@ private:
     }
 
     if (! meth) {
-      throw tl::TypeError (tl::to_string (tr ("No overload with matching arguments. Variants are:\n")) + describe_overloads (argc, kwargs));
+      throw tl::Exception (tl::to_string (tr ("No overload with matching arguments. Variants are:\n")) + describe_overloads (argc, kwargs));
     }
 
     if (candidates > 1) {
-      throw tl::TypeError (tl::to_string (tr ("Ambiguous overload variants - multiple method declarations match arguments. Variants are:\n")) + describe_overloads (argc, kwargs));
+      throw tl::Exception (tl::to_string (tr ("Ambiguous overload variants - multiple method declarations match arguments. Variants are:\n")) + describe_overloads (argc, kwargs));
     }
 
     if (is_const && ! meth->is_const ()) {

src/tl/tl/tlExpression.cc

@@ -306,12 +306,12 @@ class TL_PUBLIC ListClass
   : public EvalClass
 {
 public:
-  void execute (const ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args) const
+  void execute (const ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args, const std::map<std::string, tl::Variant> *kwargs) const
   {
     if (method == "push") {
 
-      if (args.size () != 1) {
-        throw EvalError (tl::to_string (tr ("'push' method expects one argument")), context);
+      if (args.size () != 1 || kwargs) {
+        throw EvalError (tl::to_string (tr ("'push' method expects one argument (keyword arguments not permitted)")), context);
       }
 
       object.push (args [0]);
@@ -319,7 +319,7 @@ public:
 
     } else if (method == "size") {
       
-      if (args.size () != 0) {
+      if (args.size () != 0 || kwargs) {
         throw EvalError (tl::to_string (tr ("'size' method does not accept an argument")), context);
       }
 
@@ -343,12 +343,12 @@ class TL_PUBLIC ArrayClass
   : public EvalClass
 {
 public:
-  void execute (const ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args) const
+  void execute (const ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args, const std::map<std::string, tl::Variant> *kwargs) const
   {
     if (method == "insert") {
 
-      if (args.size () != 2) {
-        throw EvalError (tl::to_string (tr ("'insert' method expects two arguments")), context);
+      if (args.size () != 2 || kwargs) {
+        throw EvalError (tl::to_string (tr ("'insert' method expects two arguments (keyword arguments not permitted)")), context);
       }
 
       object.insert (args [0], args [1]);
@@ -356,7 +356,7 @@ public:
 
     } else if (method == "size") {
       
-      if (args.size () != 0) {
+      if (args.size () != 0 || kwargs) {
         throw EvalError (tl::to_string (tr ("'size' method does not accept an argument")), context);
       }
 
@@ -364,7 +364,7 @@ public:
     
     } else if (method == "keys") {
 
-      if (args.size () != 0) {
+      if (args.size () != 0 || kwargs) {
         throw EvalError (tl::to_string (tr ("'keys' method does not accept an argument")), context);
       }
 
@@ -375,7 +375,7 @@ public:
 
     } else if (method == "values") {
 
-      if (args.size () != 0) {
+      if (args.size () != 0 || kwargs) {
         throw EvalError (tl::to_string (tr ("'keys' method does not accept an argument")), context);
       }
 
@@ -411,7 +411,7 @@ ExpressionNode::ExpressionNode (const ExpressionParserContext &context, size_t c
 }
 
 ExpressionNode::ExpressionNode (const ExpressionNode &other, const tl::Expression *expr)
-  : m_context (other.m_context)
+  : m_context (other.m_context), m_name (other.m_name)
 {
   m_context.set_expr (expr);
   m_c.reserve (other.m_c.size ());
@@ -517,7 +517,7 @@ public:
       tl::Variant o;
       std::vector <tl::Variant> vv;
       vv.push_back (*b);
-      c->execute (m_context, o, v.get (), "<", vv);
+      c->execute (m_context, o, v.get (), "<", vv, 0);
       v.swap (o);
 
     } else {
@@ -567,7 +567,7 @@ public:
       tl::Variant o;
       std::vector <tl::Variant> vv;
       vv.push_back (*b);
-      c->execute (m_context, o, v.get (), "<=", vv);
+      c->execute (m_context, o, v.get (), "<=", vv, 0);
       v.swap (o);
 
     } else {
@@ -617,7 +617,7 @@ public:
       tl::Variant o;
       std::vector <tl::Variant> vv;
       vv.push_back (*b);
-      c->execute (m_context, o, v.get (), ">", vv);
+      c->execute (m_context, o, v.get (), ">", vv, 0);
       v.swap (o);
 
     } else {
@@ -667,7 +667,7 @@ public:
       tl::Variant o;
       std::vector <tl::Variant> vv;
       vv.push_back (*b);
-      c->execute (m_context, o, v.get (), ">=", vv);
+      c->execute (m_context, o, v.get (), ">=", vv, 0);
       v.swap (o);
 
     } else {
@@ -717,7 +717,7 @@ public:
       tl::Variant o;
       std::vector <tl::Variant> vv;
       vv.push_back (*b);
-      c->execute (m_context, o, v.get (), "==", vv);
+      c->execute (m_context, o, v.get (), "==", vv, 0);
       v.swap (o);
 
     } else {
@@ -767,7 +767,7 @@ public:
       tl::Variant o;
       std::vector <tl::Variant> vv;
       vv.push_back (*b);
-      c->execute (m_context, o, v.get (), "!=", vv);
+      c->execute (m_context, o, v.get (), "!=", vv, 0);
       v.swap (o);
 
     } else {
@@ -817,7 +817,7 @@ public:
       tl::Variant o;
       std::vector <tl::Variant> vv;
       vv.push_back (*b);
-      c->execute (m_context, o, v.get (), "~", vv);
+      c->execute (m_context, o, v.get (), "~", vv, 0);
       v.swap (o);
 
       mp_eval->match_substrings ().clear ();
@@ -914,7 +914,7 @@ public:
       tl::Variant o;
       std::vector <tl::Variant> vv;
       vv.push_back (*b);
-      c->execute (m_context, o, v.get (), "!~", vv);
+      c->execute (m_context, o, v.get (), "!~", vv, 0);
       v.swap (o);
 
     } else {
@@ -1085,7 +1085,7 @@ public:
       tl::Variant o;
       std::vector <tl::Variant> vv;
       vv.push_back (*b);
-      c->execute (m_context, o, v.get (), "<<", vv);
+      c->execute (m_context, o, v.get (), "<<", vv, 0);
       v.swap (o);
 
     } else if (v->is_longlong ()) {
@@ -1141,7 +1141,7 @@ public:
       tl::Variant o;
       std::vector <tl::Variant> vv;
       vv.push_back (*b);
-      c->execute (m_context, o, v.get (), ">>", vv);
+      c->execute (m_context, o, v.get (), ">>", vv, 0);
       v.swap (o);
 
     } else if (v->is_longlong ()) {
@@ -1197,7 +1197,7 @@ public:
       tl::Variant o;
       std::vector <tl::Variant> vv;
       vv.push_back (*b);
-      c->execute (m_context, o, v.get (), "+", vv);
+      c->execute (m_context, o, v.get (), "+", vv, 0);
       v.swap (o);
 
     } else if (v->is_a_string () || b->is_a_string ()) {
@@ -1259,7 +1259,7 @@ public:
       tl::Variant o;
       std::vector <tl::Variant> vv;
       vv.push_back (*b);
-      c->execute (m_context, o, v.get (), "-", vv);
+      c->execute (m_context, o, v.get (), "-", vv, 0);
       v.swap (o);
 
     } else if (v->is_double () || b->is_double ()) {
@@ -1319,7 +1319,7 @@ public:
       tl::Variant o;
       std::vector <tl::Variant> vv;
       vv.push_back (*b);
-      c->execute (m_context, o, v.get (), "*", vv);
+      c->execute (m_context, o, v.get (), "*", vv, 0);
       v.swap (o);
 
     } else if (v->is_a_string ()) {
@@ -1409,7 +1409,7 @@ public:
       tl::Variant o;
       std::vector <tl::Variant> vv;
       vv.push_back (*b);
-      c->execute (m_context, o, v.get (), "/", vv);
+      c->execute (m_context, o, v.get (), "/", vv, 0);
       v.swap (o);
 
     } else if (v->is_double () || b->is_double ()) {
@@ -1493,7 +1493,7 @@ public:
       tl::Variant o;
       std::vector <tl::Variant> vv;
       vv.push_back (*b);
-      c->execute (m_context, o, v.get (), "%", vv);
+      c->execute (m_context, o, v.get (), "%", vv, 0);
       v.swap (o);
 
     } else if (v->is_ulonglong () || b->is_ulonglong ()) {
@@ -1565,7 +1565,7 @@ public:
       tl::Variant o;
       std::vector <tl::Variant> vv;
       vv.push_back (*b);
-      c->execute (m_context, o, v.get (), "&", vv);
+      c->execute (m_context, o, v.get (), "&", vv, 0);
       v.swap (o);
 
     } else if (v->is_ulonglong () || b->is_ulonglong ()) {
@@ -1621,7 +1621,7 @@ public:
       tl::Variant o;
       std::vector <tl::Variant> vv;
       vv.push_back (*b);
-      c->execute (m_context, o, v.get (), "|", vv);
+      c->execute (m_context, o, v.get (), "|", vv, 0);
       v.swap (o);
 
     } else if (v->is_ulonglong () || b->is_ulonglong ()) {
@@ -1677,7 +1677,7 @@ public:
       tl::Variant o;
       std::vector <tl::Variant> vv;
       vv.push_back (*b);
-      c->execute (m_context, o, v.get (), "^", vv);
+      c->execute (m_context, o, v.get (), "^", vv, 0);
       v.swap (o);
 
     } else if (v->is_ulonglong () || b->is_ulonglong ()) {
@@ -1733,7 +1733,7 @@ public:
       tl::Variant o;
       std::vector <tl::Variant> vv;
       vv.push_back (*e);
-      c->execute (m_context, o, v.get (), "[]", vv);
+      c->execute (m_context, o, v.get (), "[]", vv, 0);
       v.swap (o);
 
     } else if (v->is_list ()) {
@@ -2025,11 +2025,17 @@ public:
     m_c[0]->execute (v);
 
     std::vector <tl::Variant> vv;
+    std::map <std::string, tl::Variant> kwargs;
+
     vv.reserve (m_c.size () - 1);
     for (std::vector<ExpressionNode *>::const_iterator c = m_c.begin () + 1; c != m_c.end (); ++c) {
       EvalTarget a;
       (*c)->execute (a);
-      vv.push_back (*a);
+      if (! (*c)->name ().empty ()) {
+        kwargs [(*c)->name ()] = *a;
+      } else {
+        vv.push_back (*a);
+      }
     }
 
     const EvalClass *c = 0;
@@ -2048,7 +2054,7 @@ public:
     }
 
     tl::Variant o;
-    c->execute (m_context, o, v.get (), m_method, vv);
+    c->execute (m_context, o, v.get (), m_method, vv, kwargs.empty () ? 0 : &kwargs);
     v.swap (o);
   }
 
@@ -2188,16 +2194,26 @@ public:
   void execute (EvalTarget &v) const 
   {
     std::vector<tl::Variant> vv;
+    std::map<std::string, tl::Variant> kwargs;
+
     vv.reserve (m_c.size ());
 
     for (std::vector<ExpressionNode *>::const_iterator c = m_c.begin (); c != m_c.end (); ++c) {
       EvalTarget a;
       (*c)->execute (a);
-      vv.push_back (*a);
+      if ((*c)->name ().empty ()) {
+        vv.push_back (*a);
+      } else {
+        kwargs[(*c)->name ()] = *a;
+      }
+    }
+
+    if (! kwargs.empty () && ! mp_func->supports_keyword_parameters ()) {
+      throw EvalError (tl::to_string (tr ("Keyword parameters not permitted")), m_context);
     }
 
     tl::Variant o;
-    mp_func->execute (m_context, o, vv);
+    mp_func->execute (m_context, o, vv, kwargs.empty () ? 0 : &kwargs);
     v.swap (o);
   }
 
@@ -2939,7 +2955,7 @@ public:
     ms_functions.erase (m_name);
   }
 
-  void execute (const ExpressionParserContext &context, tl::Variant &out, const std::vector<tl::Variant> &args) const 
+  void execute (const ExpressionParserContext &context, tl::Variant &out, const std::vector<tl::Variant> &args, const std::map<std::string, tl::Variant> * /*kwargs*/) const
   {
     m_func (context, out, args);
   }
@@ -3556,8 +3572,19 @@ Eval::eval_suffix (ExpressionParserContext &ex, std::unique_ptr<ExpressionNode>
 
           do {
 
+            tl::Extractor exn = ex;
+            std::string n;
+            if (exn.try_read_word (n, "_") && exn.test ("=")) {
+              //  keyword parameter -> read name again to skip it
+              ex.read_word (n, "_");
+              ex.expect ("=");
+            } else {
+              n.clear ();
+            }
+
             std::unique_ptr<ExpressionNode> a;
             eval_assign (ex, a);
+            a->set_name (n);
             m->add_child (a.release ());
 
             if (ex.test (")")) {

src/tl/tl/tlExpression.h

@@ -186,7 +186,25 @@ public:
   /**
    *  @brief Add a child node
    */
-  void add_child (ExpressionNode *node); 
+  void add_child (ExpressionNode *node);
+
+  /**
+   *  @brief Gets the name
+   *
+   *  The name is used for named arguments for example.
+   */
+  const std::string &name () const
+  {
+    return m_name;
+  }
+
+  /**
+   *  @brief Sets the name
+   */
+  void set_name (const std::string &name)
+  {
+    m_name = name;
+  }
 
   /**
    *  @brief Execute the node
@@ -201,6 +219,7 @@ public:
 protected:
   std::vector <ExpressionNode *> m_c;
   ExpressionParserContext m_context;
+  std::string m_name;
 
   /**
    *  @brief Sets the expression parent
@@ -244,7 +263,7 @@ public:
    *
    *  If no method of this kind exists, the implementation may throw a NoMethodError.
    */
-  virtual void execute (const ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args) const = 0;
+  virtual void execute (const ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args, const std::map<std::string, tl::Variant> *kwargs) const = 0;
 };
 
 /**
@@ -263,6 +282,11 @@ public:
    */
   virtual ~EvalFunction () { }
 
+  /**
+   *  @brief Specifies whether keyword parameters are supported
+   */
+  virtual bool supports_keyword_parameters () const { return false; }
+
   /**
    *  @brief The actual execution method
    *
@@ -270,7 +294,7 @@ public:
    *  @param args The arguments of the method
    *  @return The return value 
    */
-  virtual void execute (const ExpressionParserContext &context, tl::Variant &out, const std::vector<tl::Variant> &args) const = 0;
+  virtual void execute (const ExpressionParserContext &context, tl::Variant &out, const std::vector<tl::Variant> &args, const std::map<std::string, tl::Variant> *kwargs) const = 0;
 };
 
 /**

src/tl/unit_tests/tlExpressionTests.cc

@@ -445,7 +445,7 @@ private:
 class BoxClassClass : public tl::VariantUserClassBase, private tl::EvalClass
 {
 public:
-  virtual void execute (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args) const;
+  virtual void execute (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args, const std::map<std::string, tl::Variant> *kwargs) const;
 
   virtual void *create () const { tl_assert (false); }
   virtual void destroy (void *) const { tl_assert (false); }
@@ -473,7 +473,7 @@ BoxClassClass BoxClassClass::instance;
 class BoxClass : public tl::VariantUserClassImpl<Box>, private tl::EvalClass
 {
 public:
-  virtual void execute (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args) const;
+  virtual void execute (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args, const std::map<std::string, tl::Variant> *kwargs) const;
 
   virtual const tl::EvalClass *eval_cls () const { return this; }
   static BoxClass instance;
@@ -481,7 +481,7 @@ public:
 
 BoxClass BoxClass::instance;
 
-void BoxClass::execute (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args) const 
+void BoxClass::execute (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args, const std::map<std::string, tl::Variant> * /*kwargs*/) const
 {
   if (method == "width") {
     out = object.to_user<Box> ().width ();
@@ -501,7 +501,7 @@ void BoxClass::execute (const tl::ExpressionParserContext &context, tl::Variant
   }
 }
 
-void BoxClassClass::execute (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant & /*object*/, const std::string &method, const std::vector<tl::Variant> &args) const 
+void BoxClassClass::execute (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant & /*object*/, const std::string &method, const std::vector<tl::Variant> &args, const std::map<std::string, tl::Variant> * /*kwargs*/) const
 {
   if (method == "new") {
     out = tl::Variant (new Box (args[0].to_long(), args[1].to_long(), args[2].to_long(), args[3].to_long()), &BoxClass::instance, true);
@@ -513,7 +513,7 @@ void BoxClassClass::execute (const tl::ExpressionParserContext &context, tl::Var
 class EdgeClassClass : public tl::VariantUserClassBase, private tl::EvalClass
 {
 public:
-  virtual void execute (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args) const;
+  virtual void execute (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args, const std::map<std::string, tl::Variant> *kwargs) const;
 
   virtual void *create () const { tl_assert (false); }
   virtual void destroy (void *) const { tl_assert (false); }
@@ -541,7 +541,7 @@ EdgeClassClass EdgeClassClass::instance;
 class EdgeClass : public tl::VariantUserClassImpl<Edge>,  private tl::EvalClass
 {
 public:
-  virtual void execute (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args) const 
+  virtual void execute (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args, const std::map<std::string, tl::Variant> * /*kwargs*/) const
   {
     if (method == "dx") {
       out = object.to_user<Edge> ().dx ();
@@ -566,7 +566,7 @@ public:
 EdgeClass EdgeClass::instance;
 
 void 
-EdgeClassClass::execute (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant & /*object*/, const std::string &method, const std::vector<tl::Variant> &args) const 
+EdgeClassClass::execute (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant & /*object*/, const std::string &method, const std::vector<tl::Variant> &args, const std::map<std::string, tl::Variant> * /*kwargs*/) const
 {
   if (method == "new") {
     out = tl::Variant (new Edge (args[0].to_long(), args[1].to_long(), args[2].to_long(), args[3].to_long()), &EdgeClass::instance, true);
@@ -996,7 +996,7 @@ class F0
   : public tl::EvalFunction
 {
 public:
-  void execute (const tl::ExpressionParserContext &, tl::Variant &out, const std::vector <tl::Variant> &) const
+  void execute (const tl::ExpressionParserContext &, tl::Variant &out, const std::vector <tl::Variant> &, const std::map<std::string, tl::Variant> *) const
   {
     out = tl::Variant (17);
   }
@@ -1006,7 +1006,7 @@ class F1
   : public tl::EvalFunction
 {
 public:
-  void execute (const tl::ExpressionParserContext &, tl::Variant &out, const std::vector <tl::Variant> &vv) const
+  void execute (const tl::ExpressionParserContext &, tl::Variant &out, const std::vector <tl::Variant> &vv, const std::map<std::string, tl::Variant> *) const
   {
     out = tl::Variant (vv[0].to_long() + 1);
   }
@@ -1016,7 +1016,7 @@ class F2
   : public tl::EvalFunction
 {
 public:
-  void execute (const tl::ExpressionParserContext &, tl::Variant &out, const std::vector <tl::Variant> &vv) const
+  void execute (const tl::ExpressionParserContext &, tl::Variant &out, const std::vector <tl::Variant> &vv, const std::map<std::string, tl::Variant> *) const
   {
     out = tl::Variant (vv[0].to_long() + 2);
   }
@@ -1026,7 +1026,7 @@ class F3
   : public tl::EvalFunction
 {
 public:
-  void execute (const tl::ExpressionParserContext &, tl::Variant &out, const std::vector <tl::Variant> &vv) const
+  void execute (const tl::ExpressionParserContext &, tl::Variant &out, const std::vector <tl::Variant> &vv, const std::map<std::string, tl::Variant> *) const
   {
     out = tl::Variant (vv[0].to_long() + 3);
   }