From 4fca40fc692d6cf612be21d63d578b595c8b1cc6 Mon Sep 17 00:00:00 2001
From: Paul Beckingham <paul@beckingham.net>
Date: Thu, 16 Jun 2011 20:30:48 -0400
Subject: [PATCH] Expressions

- Added Expression::eval short-circuit.
- Added int/number exlclusions for Nibbler::getDOM.
- Added Variant::boolean for exatracting filter results.
---
 src/Expression.cpp | 52 ++++++++++++++++++++++++++++++++++++++--------
 src/Nibbler.cpp    | 11 ++++++++++
 src/Variant.cpp    |  8 +++++++
 src/Variant.h      |  1 +
 4 files changed, 63 insertions(+), 9 deletions(-)

diff --git a/src/Expression.cpp b/src/Expression.cpp
index cf1c6041b..b81aa90d8 100644
--- a/src/Expression.cpp
+++ b/src/Expression.cpp
@@ -27,6 +27,7 @@
 
 #include <iostream> // TODO Remove.
 #include <sstream>
+#include <stdlib.h>
 #include <Context.h>
 #include <Lexer.h>
 #include <Date.h>
@@ -70,6 +71,12 @@ Expression::~Expression ()
 ////////////////////////////////////////////////////////////////////////////////
 bool Expression::eval (Task& task)
 {
+  // If there are no elements in the filter, then all tasks pass.
+  if (_args.size () == 0)
+    return true;
+
+  // There are elements in the filter, so the expression must be evaluated
+  // against each task.
   std::vector <Variant> value_stack;
 
   std::vector <std::pair <std::string, std::string> >::iterator arg;
@@ -88,18 +95,19 @@ bool Expression::eval (Task& task)
       // TODO Need helpers that pop, and error out if necessary.
       if (arg->first == "+")
       {
-        // TODO This needs to be type-aware.
         Variant right (value_stack.back ());
         value_stack.pop_back ();
         Variant left (value_stack.back ());
         value_stack.pop_back ();
 
+        context.debug ("eval left=" + left.format ());
+        context.debug ("eval right=" + right.format ());
         left = left + right;
+        context.debug ("eval + --> " + left.format ());
 
         value_stack.push_back (left);
       }
 
-
       else if (arg->first == "and")
       {
       }
@@ -183,15 +191,41 @@ bool Expression::eval (Task& task)
       else
         throw std::string ("Unsupported operator '") + arg->first + "'.";
     }
-/*
+
+    // It's not an operator, it's either and lvalue or some form of rvalue.
     else
-      value_stack.push_back (Variant (*arg));
-*/
+    {
+      if (arg->second == "lvalue")
+        value_stack.push_back (Variant (context.dom.get (arg->first)));
+
+      else if (arg->second == "int")
+        value_stack.push_back (Variant ((int) strtol (arg->first.c_str (), NULL, 10)));
+
+      else if (arg->second == "number")
+        value_stack.push_back (Variant (strtod (arg->first.c_str (), NULL)));
+
+      else if (arg->second == "rvalue" ||
+               arg->second == "string" ||
+               arg->second == "rx")
+        value_stack.push_back (Variant (arg->first));
+
+      else
+        throw std::string ("Error: Expression::eval unrecognized operand '") +   + "'.";
+    }
+
   }
 
-  // TODO Any more values on stack?  Error.
-  // TODO Return the value that is on the stack.
-  return false;
+  // Coerce stack element to boolean.
+  Variant result (value_stack.back ());
+  context.debug ("eval result=" + result.format ());
+  value_stack.pop_back ();
+  bool pass_fail = result.boolean ();
+
+  // Check for stack remnants.
+  if (value_stack.size ())
+    throw std::string ("Error: Expression::eval found extra items on the stack.");
+
+  return pass_fail;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -316,7 +350,7 @@ void Expression::expand_tokens ()
           temp.push_back (std::make_pair (s, "op"));
 
         else if (n.getDOM (s))
-          temp.push_back (std::make_pair (s, "dom"));
+          temp.push_back (std::make_pair (s, "lvalue"));
 
         else if (n.getNumber (d))
           temp.push_back (std::make_pair (format (d), "number"));
diff --git a/src/Nibbler.cpp b/src/Nibbler.cpp
index 33454c315..a1f22dab1 100644
--- a/src/Nibbler.cpp
+++ b/src/Nibbler.cpp
@@ -927,6 +927,17 @@ bool Nibbler::getDOM (std::string& found)
   if (i > mCursor)
   {
     found = mInput.substr (start, i - start);
+
+    // If found is simple a number, then it is not a DOM reference.
+    double d;
+    Nibbler exclusion (found);
+    if (exclusion.getNumber (d) && exclusion.depleted ())
+      return false;
+
+    int in;
+    if (exclusion.getInt (in) && exclusion.depleted ())
+      return false;
+
     mCursor = i;
     return true;
   }
diff --git a/src/Variant.cpp b/src/Variant.cpp
index c4eb03abb..7317b39fb 100644
--- a/src/Variant.cpp
+++ b/src/Variant.cpp
@@ -852,4 +852,12 @@ void Variant::promote (Variant& lhs, Variant& rhs)
 }
 
 ////////////////////////////////////////////////////////////////////////////////
+// Casts to boolean and returns the value.  Used to evaluating expression
+// results.
+bool Variant::boolean ()
+{
+  cast (v_boolean);
+  return mBool;
+}
 
+////////////////////////////////////////////////////////////////////////////////
diff --git a/src/Variant.h b/src/Variant.h
index d222d4118..70fc616f8 100644
--- a/src/Variant.h
+++ b/src/Variant.h
@@ -90,6 +90,7 @@ public:
   void cast (const variant_type);
   variant_type type ();
   void promote (Variant&, Variant&);
+  bool boolean ();
 
 private:
   variant_type mType;