5 files changed, 43 insertions, 15 deletions

diff --git a/TODO.rst b/TODO.rst
index d853b36..69a9c43 100644
--- a/TODO.rst
+++ b/TODO.rst
@@ -1,5 +1,4 @@
-- More sophisticated type system
-  - Number system && proper arithmetic
-  - Cons support
+- More sophisticated parser
+- GMP
 - Quotation
 - Add macro support
diff --git a/builtin.h b/builtin.h
index ab52d5a..322e82e 100644
--- a/builtin.h
+++ b/builtin.h
@@ -25,7 +25,7 @@ class CompNumObj: public InexactNumObj {
 
         /** Construct a complex number */
         CompNumObj(double _real, double _imag);
-        /** Try to construct an RealNumObj object 
+        /** Try to construct an CompNumObj object 
          * @return NULL if failed
          */
         static CompNumObj *from_string(string repr);
@@ -85,7 +85,7 @@ class RatNumObj: public ExactNumObj {
         int a, b;
         /** Construct a rational number */
         RatNumObj(int _a, int _b);
-        /** Try to construct an RealNumObj object 
+        /** Try to construct an RatNumObj object 
          * @return NULL if failed
          */
         static RatNumObj *from_string(string repr);
diff --git a/model.cpp b/model.cpp
index 3703f1d..4f0e1c5 100644
--- a/model.cpp
+++ b/model.cpp
@@ -94,7 +94,7 @@ RetAddr::RetAddr(Cons *_addr) : FrameObj(CLS_RET_ADDR), addr(_addr) {}
 string RetAddr::_debug_repr() { return string("#<Return Address>"); }
 #endif
 
-UnspecObj::UnspecObj() : EvalObj() {}
+UnspecObj::UnspecObj() : EvalObj(CLS_SIM_OBJ) {}
 
 string UnspecObj::ext_repr() { return string("#<Unspecified>"); }
 
@@ -150,7 +150,7 @@ string ProcObj::_debug_repr() { return ext_repr(); }
 
 SpecialOptObj::SpecialOptObj() : OptObj() {}
 
-BoolObj::BoolObj(bool _val) : EvalObj(), val(_val) {}
+BoolObj::BoolObj(bool _val) : EvalObj(CLS_SIM_OBJ), val(_val) {}
 
 bool BoolObj::is_true() { return val; }
 
@@ -161,6 +161,17 @@ NumObj::NumObj(NumLvl _level, bool _exactness) :
 
 bool NumObj::is_exact() { return exactness; }
 
+StrObj::StrObj(string _str) : EvalObj(CLS_SIM_OBJ), str(_str) {}
+
+string StrObj::ext_repr() { return str; }
+
+StrObj *StrObj::from_string(string repr) {
+    int len = repr.length();
+    if (repr[0] == '\"' && repr[len - 1] == '\"')
+        return new StrObj(repr.substr(1, len - 2));
+    return NULL;
+}
+
 BuiltinProcObj::BuiltinProcObj(BuiltinProc f, string _name) :
     OptObj(), handler(f), name(_name) {}
 
diff --git a/model.h b/model.h
index d402b2b..f883032 100644
--- a/model.h
+++ b/model.h
@@ -259,6 +259,10 @@ class BoolObj: public EvalObj {
         BoolObj(bool);                  /**< Converts a C bool value to a BoolObj*/
         bool is_true();                 /**< Override EvalObj `is_true()` */
         string ext_repr();
+        /** Try to construct an BoolObj object 
+         * @return NULL if failed
+         */
+        static BoolObj *from_string(string repr);
 };
 
 /** @class NumObj
@@ -290,6 +294,23 @@ class NumObj: public EvalObj {
         virtual bool eq(NumObj *r) = 0;
 };
 
+/** @class StrObj
+ * String support
+ */
+class StrObj: public EvalObj {
+    public:
+        string str;
+        
+        /** Construct a string object */
+        StrObj(string str);
+        /** Try to construct an StrObj object 
+         * @return NULL if failed
+         */
+        static StrObj *from_string(string repr);
+        string ext_repr();
+};
+
+
 typedef map<string, EvalObj*> Str2EvalObj;
 /** @class Environment
  * The environment of current evaluation, i.e. the local variable binding 
diff --git a/parser.cpp b/parser.cpp
index cb8695f..07ca066 100644
--- a/parser.cpp
+++ b/parser.cpp
@@ -105,14 +105,11 @@ ASTGenerator::ASTGenerator() {}
 
 EvalObj *ASTGenerator::to_obj(const string &str) {
     EvalObj *res = NULL;
-    if ((res = IntNumObj::from_string(str)))
-        return res;
-    if ((res = RatNumObj::from_string(str)))
-        return res;
-    if ((res = RealNumObj::from_string(str)))
-        return res;
-    if ((res = CompNumObj::from_string(str)))
-        return res;
+    if ((res = IntNumObj::from_string(str))) return res;
+    if ((res = RatNumObj::from_string(str))) return res;
+    if ((res = RealNumObj::from_string(str))) return res;
+    if ((res = CompNumObj::from_string(str))) return res;
+    if ((res = StrObj::from_string(str))) return res;
     return new SymObj(str);
 }
 Cons *ASTGenerator::absorb(Tokenizor *tk) {