Moved 'choice' property to SemanticValues.

README.md

@@ -12,6 +12,8 @@ The PEG syntax is well described on page 2 in the [document](http://pdos.csail.m
   * `~` (Ignore operator)
   * `\x??` (Hex number char)
 
+This library is a [*Packrat*](http://pdos.csail.mit.edu/~baford/packrat/thesis/thesis.pdf) parser which supports the linear-time parsing.
+
 How to use
 ----------
 
@@ -48,12 +50,13 @@ int main(void) {
         [](const SemanticValues& sv) { return sv[0]; }          // 2nd choice
     };
 
-    parser["Multitive"] = {
-        nullptr,                                                // Default action
-        [](const SemanticValues& sv) {
-            return sv[0].val.get<int>() * sv[1].val.get<int>(); // 1st choice
-        },
-        [](const SemanticValues& sv) { return sv[0]; }          // 2nd choice
+    parser["Multitive"] = [](const SemanticValues& sv) {
+        switch (sv.choice) {
+        case 0:  // 1st choice
+            return sv[0].val.get<int>() * sv[1].val.get<int>();
+        default: // 2nd choice
+            return sv[0].val.get<int>();
+        }
     };
 
     /* This action is not necessary.
@@ -95,8 +98,9 @@ struct SemanticValue {
 
 struct SemanticValues : protected std::vector<SemanticValue>
 {
-    const char* s; // Token start
-    size_t      l; // Token length
+    const char* s;      // Token start
+    size_t      l;      // Token length
+    size_t      choice; // Choice number (0 based index)
 }
 ```
 
@@ -292,7 +296,6 @@ Tested Compilers
 TODO
 ----
 
-  * Linear-time parsing (Packrat parsing)
   * Optimization of grammars
   * Unicode support
 

peglib.h

@@ -186,8 +186,9 @@ struct SemanticValues : protected std::vector<SemanticValue>
 {
     const char* s;
     size_t      l;
+    size_t      choice;
 
-    SemanticValues() : s(nullptr), l(0) {}
+    SemanticValues() : s(nullptr), l(0), choice(0) {}
 
     typedef SemanticValue T;
     using std::vector<T>::iterator;
@@ -429,7 +430,6 @@ struct Context
     const char*                                  s;
     size_t                                       l;
 
-    size_t                                       choice;
     const char*                                  error_ptr;
     const char*                                  msg; // TODO: should be `int`.
 
@@ -604,8 +604,8 @@ public:
                 }
                 sv.s = chldsv.s;
                 sv.l = chldsv.l;
+                sv.choice = id;
                 c.pop();
-                c.choice = id;
                 return len;
             }
             id++;
@@ -1190,7 +1190,7 @@ inline int Holder::parse(const char* s, size_t l, SemanticValues& sv, Context& c
         if (success(len) && !outer_->ignore) {
             assert(!outer_->actions.empty());
 
-            auto i = c.choice + 1; // Index 0 is for the default action
+            auto i = chldsv.choice + 1; // Index 0 is for the default action
             const auto& action = (i < outer_->actions.size() && outer_->actions[i])
                 ? outer_->actions[i]
                 : outer_->actions[0];

test/test.cc

@@ -252,7 +252,12 @@ TEST_CASE("Simple calculator test", "[general]")
     };
 
     parser["Multitive"] = [](const SemanticValues& sv) {
-        return sv.size() == 1 ? sv[0].val.get<int>() : sv[0].val.get<int>() * sv[1].val.get<int>();
+        switch (sv.choice) {
+        case 0:  // Action for the first choice
+            return sv[0].val.get<int>() * sv[1].val.get<int>();
+        default: // Action for the second choice
+            return sv[0].val.get<int>();
+        }
     };
 
     parser["Number"] = [](const char* s, size_t l) {