removed `skip` field from Pair, use `next` to make jumps insteadskip_removal

author: Teddy <ted.sybil@gmail.com> 2013-08-09 12:41:49 +0800
committer: Teddy <ted.sybil@gmail.com> 2013-08-09 12:41:49 +0800
commit: 01b2c905872ff38d5d8291f2f8de92c2771f183f (patch)
tree: bd3622d29d29cc1f7205a79eca9a15ee377c719a
parent: 0c606491335e99017897a7710461214412243dd7 (diff)
6 files changed, 90 insertions, 67 deletions
diff --git a/builtin.cpp b/builtin.cpp
index 7c5f3c7..27b3ee7 100644
--- a/builtin.cpp
+++ b/builtin.cpp
@@ -543,59 +543,53 @@ void SpecialOptIf::prepare(Pair *pc) {
         throw TokenError(name, RUN_ERR_WRONG_NUM_OF_ARGS)
     state = 0;  // Prepared
 
+    Pair *first, *second, *third;
+
     if (pc->cdr->is_pair_obj())
-        pc = TO_PAIR(pc->cdr);
+        first = TO_PAIR(pc->cdr);
     else 
         IF_EXP_ERR;
-//    if (pc == empty_list)
-//        IF_EXP_ERR;
-
-    pc->skip = false;
 
-    if (pc->cdr->is_pair_obj())
-        pc = TO_PAIR(pc->cdr);
+    if (first->cdr->is_pair_obj())
+        second = TO_PAIR(first->cdr);
     else
         IF_EXP_ERR;
- //   if (pc == empty_list)
- //       IF_EXP_ERR;
 
-    pc->skip = true;
-    if (pc->cdr != empty_list)
+    if (second->cdr != empty_list)
     {
-        if (pc->cdr->is_pair_obj())
+        if (second->cdr->is_pair_obj())
         {
-            TO_PAIR(pc->cdr)->skip = true;
-            if (TO_PAIR(pc->cdr)->cdr != empty_list)
+            third = TO_PAIR(second->cdr);
+            if (third->cdr != empty_list)
                 IF_EXP_ERR;
         }
         else
             IF_EXP_ERR;
     }
+    pc->next = first;
+    first->next = NULL; // skip <consequence> and <alternative>
 }
 
 void SpecialOptIf::pre_call(ArgList *args, Pair *pc,
         Environment *envt) {
-    // static_cast because it's a call invocation
-    pc = TO_PAIR(TO_PAIR(pc->car)->cdr); 
+    // prepare has guaranteed ...
+    pc = TO_PAIR(pc->car);
+    Pair *first = TO_PAIR(pc->cdr); 
+    Pair *second = TO_PAIR(first->cdr);
+    Pair *third = TO_PAIR(second->cdr);
 
     // Condition evaluated and the decision is made
     state = 1;
 
     if (TO_PAIR(args->cdr)->car->is_true())
     {
-        pc->skip = true;
-        pc = TO_PAIR(pc->cdr);
-        pc->skip = false;
-        if (pc->cdr != empty_list)
-            TO_PAIR(pc->cdr)->skip = true; // Eval the former
+        pc->next = second;
+        second->next = NULL;
     }
     else
     {
-        pc->skip = true;
-        pc = TO_PAIR(pc->cdr);
-        pc->skip = true;
-        if (pc->cdr != empty_list)
-            TO_PAIR(pc->cdr)->skip = false; //Eval the latter
+        pc->next = third;
+        third->next = NULL;
     }
 }
 
@@ -628,7 +622,7 @@ ReprCons *SpecialOptIf::get_repr_cons() {
 }
 
 SpecialOptLambda::SpecialOptLambda() : SpecialOptObj("lambda") {}
-#define FILL_MARKS(pc, flag)  \
+#define CHECK_COM(pc)  \
 do  \
 { \
     EvalObj *nptr; \
@@ -638,7 +632,6 @@ do  \
         if ((nptr = ptr->cdr)->is_pair_obj()) \
             ptr = TO_PAIR(nptr); \
         else break; \
-        ptr->skip = flag; \
     } \
     if (ptr->cdr != empty_list) \
         throw TokenError(name, RUN_ERR_WRONG_NUM_OF_ARGS); \
@@ -673,7 +666,8 @@ while (0)
 
 void SpecialOptLambda::prepare(Pair *pc) {
     // Do not evaluate anything
-    FILL_MARKS(pc, true);
+    CHECK_COM(pc);
+    pc->next = NULL;
 }
 
 Pair *SpecialOptLambda::call(ArgList *args, Environment * &envt, 
@@ -684,22 +678,22 @@ Pair *SpecialOptLambda::call(ArgList *args, Environment * &envt,
     // TODO: remove the following two lines?
     if (pc->cdr == empty_list)
         throw TokenError(name, SYN_ERR_EMPTY_PARA_LIST);
-    if (TO_PAIR(pc->cdr)->cdr == empty_list)
+    Pair *first = TO_PAIR(pc->cdr);
+    // <body> is expected
+    if (first->cdr == empty_list)
         throw TokenError(name, SYN_ERR_MISS_OR_EXTRA_EXP);
-
-     // Clear the flag to avoid side-effects (e.g. proc calling)
-    FILL_MARKS(pc, false);
+    
+    // Restore the next pointer
+    pc->next = TO_PAIR(pc->cdr);            // CHECK_COM made it always okay
    
-    pc = TO_PAIR(pc->cdr);                  // Now pointintg to params
-    if (pc->car->is_simple_obj())
-        CHECK_SYMBOL(pc->car);
+    if (first->car->is_simple_obj())
+        CHECK_SYMBOL(first->car);
     else
-        CHECK_PARA_LIST(pc->car);
-    EvalObj *params = pc->car;
+        CHECK_PARA_LIST(first->car);
+    EvalObj *params = first->car;
 
     // store a list of expressions inside <body>
-
-    Pair *body = TO_PAIR(pc->cdr);       // Truncate the expression list
+    Pair *body = TO_PAIR(first->cdr);       // Truncate the expression list
     for (Pair *ptr = body; ptr != empty_list; ptr = TO_PAIR(ptr->cdr))
         ptr->next = NULL;    // Make each expression an orphan
 
@@ -716,16 +710,22 @@ SpecialOptDefine::SpecialOptDefine() : SpecialOptObj("define") {}
 void SpecialOptDefine::prepare(Pair *pc) {
     if (!pc->cdr->is_pair_obj())
         throw TokenError(name, RUN_ERR_WRONG_NUM_OF_ARGS);
-
-    if (TO_PAIR(pc->cdr)->car->is_simple_obj())  // Simple value assignment
+    Pair *first = TO_PAIR(pc->cdr), *second;
+    if (first->car->is_simple_obj())  // Simple value assignment
     {
-        pc = TO_PAIR(pc->cdr);
-        if (!pc->cdr->is_pair_obj())
+        if (!first->cdr->is_pair_obj())
+            throw TokenError(name, RUN_ERR_WRONG_NUM_OF_ARGS);
+        second = TO_PAIR(first->cdr);
+        if (second->cdr != empty_list)
             throw TokenError(name, RUN_ERR_WRONG_NUM_OF_ARGS);
-        pc->skip = true;           // Skip the identifier
-        TO_PAIR(pc->cdr)->skip = false; 
-    }                                   // Procedure definition
-    else FILL_MARKS(pc, true);          // Skip all parts
+        pc->next = second;                      // Skip the identifier
+        second->next = NULL;
+    }                                           // Procedure definition
+    else 
+    {
+        CHECK_COM(pc);
+        pc->next = NULL; // Skip all parts
+    }
 }
 
 Pair *SpecialOptDefine::call(ArgList *args, Environment * &envt, 
@@ -739,7 +739,6 @@ Pair *SpecialOptDefine::call(ArgList *args, Environment * &envt,
     {
         if (!first->is_sym_obj())
             throw TokenError(first->ext_repr(), SYN_ERR_NOT_AN_ID);
-        ARGS_EXACTLY_TWO;
         id = static_cast<SymObj*>(first);
         obj = TO_PAIR(args->cdr)->car;
     }
@@ -758,8 +757,9 @@ Pair *SpecialOptDefine::call(ArgList *args, Environment * &envt,
 
         id = static_cast<SymObj*>(plst->car);
         EvalObj *params = plst->cdr;
-        // Clear the flag to avoid side-effects (e.g. proc calling)
-        FILL_MARKS(pc, false);
+        
+        // Restore the next pointer
+        pc->next = TO_PAIR(pc->cdr);
 
         Pair *body = TO_PAIR(TO_PAIR(pc->cdr)->cdr);   // Truncate the expression list
 
@@ -784,16 +784,17 @@ void SpecialOptSet::prepare(Pair *pc) {
     if (!pc->cdr->is_pair_obj())
         throw TokenError(name, RUN_ERR_WRONG_NUM_OF_ARGS);
 
-    pc = TO_PAIR(pc->cdr);
-
-    pc->skip = true;       // Skip the identifier
+    Pair *first = TO_PAIR(pc->cdr), *second;
 
-    if (!pc->cdr->is_pair_obj())
+    if (!first->is_pair_obj())
         throw TokenError(name, RUN_ERR_WRONG_NUM_OF_ARGS);
 
-    pc = TO_PAIR(pc->cdr);
+    second = TO_PAIR(pc->cdr);
+    if (second->cdr != empty_list) 
+        throw TokenError(name, RUN_ERR_WRONG_NUM_OF_ARGS);
 
-    pc->skip = false; 
+    pc->next = second;
+    second->next = NULL;
 }
 
 Pair *SpecialOptSet::call(ArgList *args, Environment * &envt, 
@@ -804,7 +805,6 @@ Pair *SpecialOptSet::call(ArgList *args, Environment * &envt,
 
     if (!first->is_sym_obj())
         throw TokenError(first->ext_repr(), SYN_ERR_NOT_AN_ID);
-    ARGS_EXACTLY_TWO;
 
     SymObj *id = static_cast<SymObj*>(first);
 
@@ -824,7 +824,8 @@ SpecialOptQuote::SpecialOptQuote() : SpecialOptObj("quote") {}
 
 void SpecialOptQuote::prepare(Pair *pc) {
     // Do not evaluate anything
-    FILL_MARKS(pc, true);
+    CHECK_COM(pc);
+    pc->next = NULL;
 }
 
 Pair *SpecialOptQuote::call(ArgList *args, Environment * &envt, 
@@ -832,7 +833,7 @@ Pair *SpecialOptQuote::call(ArgList *args, Environment * &envt,
     Pair *ret_addr = static_cast<RetAddr*>(*top_ptr)->addr;
     Pair *pc = static_cast<Pair*>(ret_addr->car);
     // revert
-    FILL_MARKS(pc, false);
+    pc->next = TO_PAIR(pc->cdr);
     *top_ptr++ = TO_PAIR(pc->cdr)->car;
     return ret_addr->next;
 }
diff --git a/eval.cpp b/eval.cpp
index aa4f729..fddd14d 100644
--- a/eval.cpp
+++ b/eval.cpp
@@ -95,7 +95,7 @@ EvalObj *Evaluator::run_expr(Pair *prog) {
     {
         if (top_ptr == eval_stack + EVAL_STACK_SIZE)
             throw TokenError("Evaluation", RUN_ERR_STACK_OVERFLOW);
-        for (; pc && pc->skip; pc = pc->next);
+//        for (; pc && pc->skip; pc = pc->next);
         if (pc)
             push(pc, top_ptr, envt);
         else
diff --git a/main.cpp b/main.cpp
index 8f7683f..db635e8 100644
--- a/main.cpp
+++ b/main.cpp
@@ -6,7 +6,7 @@
 #include <cstdio>
 
 int main() {
-    //freopen("in.scm", "r", stdin);
+    freopen("in.scm", "r", stdin);
     Tokenizor *tk = new Tokenizor();
     ASTGenerator *ast = new ASTGenerator();
     Evaluator *eval = new Evaluator();
diff --git a/model.cpp b/model.cpp
index 6c5e4a0..f5ed609 100644
--- a/model.cpp
+++ b/model.cpp
@@ -89,9 +89,13 @@ string EvalObj::ext_repr() {
         {
             top_ptr--;
             obj = (*top_ptr)->next("");
-            *(++top_ptr) = obj->get_repr_cons();
-            if (hash.count((*top_ptr)->ori))
-                *top_ptr = new ReprStr("#inf#");
+            if (obj)
+            {
+                *(++top_ptr) = obj->get_repr_cons();
+                if (hash.count((*top_ptr)->ori))
+                    *top_ptr = new ReprStr("#inf#");
+            }
+            else *top_ptr = new ReprStr((*top_ptr)->repr);
         }
         top_ptr++;
     }
@@ -102,7 +106,7 @@ string EvalObj::ext_repr() {
 }
 
 Pair::Pair(EvalObj *_car, EvalObj *_cdr) : 
-    EvalObj(CLS_PAIR_OBJ), car(_car), cdr(_cdr), skip(false), 
+    EvalObj(CLS_PAIR_OBJ), car(_car), cdr(_cdr), 
     next(NULL) {}
 
 ReprCons *Pair::get_repr_cons() {
diff --git a/model.h b/model.h
index 7a53c8e..a4c6a1f 100644
--- a/model.h
+++ b/model.h
@@ -127,7 +127,6 @@ class Pair : public EvalObj {
     public:
         EvalObj *car;                   /**< car (as in Scheme) */
         EvalObj *cdr;                      /**< cdr (as in Scheme) */
-        bool skip;                      /**< Wether to skip the current branch */
         Pair* next;                     /**< The next branch in effect */
 
         Pair(EvalObj *car, EvalObj *cdr);  /**< Create a Pair (car . cdr) */
diff --git a/robust_test.scm b/robust_test.scm
index 637d9cd..9f5c798 100644
--- a/robust_test.scm
+++ b/robust_test.scm
@@ -147,3 +147,22 @@ t
 (display . 0)
 (display 0 . 0)
 (display t)
+
+(define)
+(define x)
+(define 1)
+(define x x)
+(define x 1 2)
+(define x . 1)
+(define x 1 . 2)
+(define ())
+(define (f))
+(define (f . ) 1)
+(define () 3)
+
+(lambda)
+(lambda ())
+(lambda 1)
+(lambda () '(1 2 3))
+(lambda () 1 2 3)
+(lambda #() 1)
author	Teddy <ted.sybil@gmail.com>	2013-08-09 12:41:49 +0800
committer	Teddy <ted.sybil@gmail.com>	2013-08-09 12:41:49 +0800
commit	01b2c905872ff38d5d8291f2f8de92c2771f183f (patch)
tree	bd3622d29d29cc1f7205a79eca9a15ee377c719a
parent	0c606491335e99017897a7710461214412243dd7 (diff)