Introduce a 'tie' operator '~' to join lists.

Author: Kasper Peeters

cmake/version.cmake

@@ -1,7 +1,7 @@
 set(CADABRA_VERSION_MAJOR 2)
 set(CADABRA_VERSION_MINOR 3)
 set(CADABRA_VERSION_PATCH 9)
-set(CADABRA_VERSION_TWEAK 3)
+set(CADABRA_VERSION_TWEAK 4)
 set(COPYRIGHT_YEARS "2001-2022")
 math(EXPR SYSTEM_BITS "${CMAKE_SIZEOF_VOID_P} * 8")
 find_program(GIT git PATHS ${GIT_DIR})

core/Cleanup.cc

@@ -48,6 +48,8 @@ namespace cadabra {
 			changed = changed || res;
 			if(*it->name=="\\comma")                         res = cleanup_comma(kernel, tr, it);
 			changed = changed || res;
+			if(*it->name=="\\tie")                           res = cleanup_tie(kernel, tr, it);
+			changed = changed || res;
 			if(*it->name=="\\components")                    res = cleanup_components(kernel, tr, it);
 			changed = changed || res;
 
@@ -871,6 +873,29 @@ namespace cadabra {
 		else return false;
 		}
 
+	bool cleanup_tie(const Kernel& k, Ex& tr, Ex::iterator& it)
+		{
+		// Are all siblings lists?
+		Ex::sibling_iterator sib = tr.begin(it);
+		while(sib!=tr.end(it)) {
+			if(*sib->name!="\\comma")
+				return false;
+			++sib;
+			}
+		
+		// All siblings are lists. Join them together into one
+		// long list.
+		it->name = name_set.insert("\\comma").first;
+		sib=tr.begin(it);
+		while(sib!=tr.end(it)) {
+			auto nxt = sib;
+			++nxt;
+			tr.flatten_and_erase(sib);
+			sib=nxt;
+			}
+		return true;
+		}
+
 	void cleanup_dispatch_deep(const Kernel& k, Ex& tr, dispatcher_t dispatch)
 		{
 		Ex::iterator top=tr.begin();

core/Cleanup.hh

@@ -77,6 +77,7 @@ namespace cadabra {
 	bool cleanup_kronecker(const Kernel& k, Ex&, Ex::iterator& it);
 	bool cleanup_exterior_derivative(const Kernel& k, Ex&, Ex::iterator& it);
 	bool cleanup_comma(const Kernel&k, Ex&, Ex::iterator& it);
+	bool cleanup_tie(const Kernel&k, Ex&, Ex::iterator& it);	
 
 	/// Given a node with a non-unit multiplier, push this multiplier
 	/// down the tree if the node is not allowed to have a non-unit

tests/programming.cdb

@@ -283,3 +283,11 @@ def test13():
     print("Test 13 passed")
 
 test13()
+
+def test14():
+    __cdbkernel__ = create_scope()
+    ex:={A,B} ~ {C,D};
+    assert(ex==${A,B,C,D}$)
+    print("Test 14 passed")
+
+test14()

web2/cadabra2/.gitignore

@@ -11,3 +11,4 @@
 algo_toc.html
 prop_toc.html
 packages_toc.html
+source/the_cadabra_book.pdf

web2/cadabra2/source/changelog.html

@@ -28,6 +28,8 @@ <h3>github master (2.3.9)</h3>
   <li>Fix for Python 3.10.x.</li>
   <li>Fix for automatic cleanup of <tt>Diagonal</tt> objects.</li>
   <li>Fix crash with tab-completion.</li>
+  <li>Make '+' operator add lists component-wise, and introduce the
+  tie operator '~' to join lists.</li>
 </ul>
 
 <a name="2.3.8"></a>