directed_changes

include/MiniLua/sourcechange.hpp

@@ -110,6 +110,11 @@ inline eval_result_t operator<< (const eval_result_t& lhs, const source_change_t
     return eval_success(get_val(lhs), get_sc(lhs) & rhs);
 }
 
+// helper functions to name and choose the source change variants
+optional<string> default_source_change_label(const val& v);
+vector<string> source_change_labels(const val& v);
+optional<shared_ptr<SourceChange>> get_sc_for_hint(const val& v, const string& hint);
+
 }
 }
 

src/core/sourcechange.cpp

@@ -72,5 +72,165 @@ vector<LuaToken> ApplySCVisitor::apply_changes(const vector<LuaToken>& tokens) {
     return new_tokens;
 }
 
+optional<string> default_source_change_label(const val& v) {
+    if (!v.source)
+        return nullopt;
+
+    auto possible_changes = v.forceValue(v);
+
+    if (!possible_changes)
+        return nullopt;
+
+    ApplySCVisitor visitor;
+    (*possible_changes)->accept(visitor);
+    for (const auto& c : visitor.changes) {
+        if (c.hint != "" && c.hint != "?")
+            return c.to_string();
+    }
+
+    return visitor.changes.front().to_string();
+}
+
+vector<string> source_change_labels(const val& v) {
+    if (!v.source)
+        return vector<string>();
+
+    auto possible_changes = v.forceValue(v);
+
+    if (!possible_changes)
+        return vector<string>();
+
+    vector<string> result;
+
+    struct SCLabelVisior : ApplySCVisitor {
+        virtual void visit(const SourceChangeOr& sc_or) override {
+            for (const auto& c : sc_or.alternatives) {
+                c->accept(*this);
+            }
+        }
+
+        virtual void visit(const SourceChangeAnd& sc_and) override {
+            if (!sc_and.changes.empty())
+                sc_and.changes.back()->accept(*this);
+        }
+
+    } visitor;
+
+    (*possible_changes)->accept(visitor);
+    for (const auto& c : visitor.changes) {
+        result.push_back(c.to_string());
+    }
+
+    return result;
+}
+
+/*
+ * removes the first alternative from a source change recursively. It does a
+ * depth first search for a source assignment and removes it, removing empty
+ * or/and nodes in the process.
+ *
+ * Precondition: the source changes must result from a call to x.forceValue(x)
+ * as it compares the match and replacement in the SourceAssignment to discard
+ * any SourceAssignments that do not influence the current source change.
+ * (probably not needed?)
+ *
+ * It returns true if a matching assignment was found, false otherwise.
+ */
+
+bool remove_alternative(shared_ptr<SourceChange>& changes) {
+    if (auto node = dynamic_pointer_cast<SourceAssignment>(changes)) {
+        if (node->token.match == node->replacement) {
+            // the node is a possibility to change the source -> return true
+            return true;
+        }
+    } else if (auto node = dynamic_pointer_cast<SourceChangeAnd>(changes)) {
+        for (unsigned i = 0; i < node->changes.size(); ++i) {
+            auto& c = node->changes[i];
+            if (remove_alternative(c)) {
+                if (auto child_node = dynamic_pointer_cast<SourceChangeOr>(c); child_node && child_node->alternatives.empty()) {
+                    node->changes.erase(begin(node->changes) + i);
+                } else if (auto child_node = dynamic_pointer_cast<SourceChangeAnd>(c); child_node && child_node->changes.empty()) {
+                    node->changes.erase(begin(node->changes) + i);
+                } else if (auto child_node = dynamic_pointer_cast<SourceAssignment>(c); child_node) {
+                    node->changes.erase(begin(node->changes) + i);
+                }
+                return true;
+            }
+        }
+        return false;
+    } else if (auto node = dynamic_pointer_cast<SourceChangeOr>(changes)) {
+        for (unsigned i = 0; i < node->alternatives.size(); ++i) {
+            auto& c = node->alternatives[i];
+            if (remove_alternative(c)) {
+                if (auto child_node = dynamic_pointer_cast<SourceChangeOr>(c); child_node && child_node->alternatives.empty()) {
+                    node->alternatives.erase(begin(node->alternatives) + i);
+                } else if (auto child_node = dynamic_pointer_cast<SourceChangeAnd>(c); child_node && child_node->changes.empty()) {
+                    node->alternatives.erase(begin(node->alternatives) + i);
+                } else if (auto child_node = dynamic_pointer_cast<SourceAssignment>(c); child_node) {
+                    node->alternatives.erase(begin(node->alternatives) + i);
+                }
+                return true;
+            }
+        }
+        return false;
+    }
+    return false;
+}
+
+/*
+ * get the source change, so that modifications to v cause a change of the
+ * source identified by hint. This is done by inserting $ operator to direct the
+ * changes to the desired source and not other alternatives.
+ *
+ * Example:
+ * a = 5
+ * b = 3
+ * x = a+b
+ *
+ * get_sc_for_hint(x, "b") => change 5 -> $5
+ *
+ * The hint is an attempt to enumerate the
+ * different alternatives for source changes. A more sophisticated structure
+ * than a string is probably necessary in the future.
+ */
+
+optional<shared_ptr<SourceChange>> get_sc_for_hint(const val& v, const string& hint) {
+    if (!v.source)
+        return nullopt;
+
+    auto possible_changes = v.forceValue(v);
+
+    if (!possible_changes)
+        return nullopt;
+
+    auto source_changes = make_shared<SourceChangeAnd>();
+
+    for(;;) {
+        ApplySCVisitor visitor;
+        (*possible_changes)->accept(visitor);
+        for (const auto& c : visitor.changes) {
+            std::cout << c.hint << std::endl;
+            if (c.to_string() == hint) {
+                // we don't have to do more!
+                return source_changes;
+            }
+        }
+
+        if (visitor.changes.empty())
+            break;
+
+        // remove current alternative and add it as a source change with $ to source_changes
+        remove_alternative(*possible_changes);
+        for (const auto& c : visitor.changes) {
+            if (c.token.match == c.replacement) {
+                source_changes->changes.push_back(SourceAssignment::create(c.token, "$" + c.replacement));
+            }
+        }
+    }
+
+    // We could not change the source to modify hint :-(
+    return nullopt;
+}
+
 }
 }

src/core/sourceexp.cpp

@@ -238,6 +238,7 @@ source_change_t sourceunop::forceValue(const val& new_v) const {
             auto res_and = make_shared<SourceChangeAnd>();
             res_and->changes.push_back(*result);
             res_and->changes.push_back(SourceAssignment::create(op, ""));
+            res_and->changes.back()->hint = identifier;
             res_or->alternatives.push_back(res_and);
         }