1 files changed, 91 insertions, 0 deletions
diff --git a/eval.cpp b/eval.cpp
new file mode 100644
index 0000000..279f8c4
--- /dev/null
+++ b/eval.cpp
@@ -0,0 +1,91 @@
+#include "eval.h"
+#include "builtin.h"
+#include <cstdio>
+
+extern Cons *empty_list;
+const int EVAL_STACK_SIZE = 65536;
+FrameObj *eval_stack[EVAL_STACK_SIZE];
+
+void Evaluator::add_builtin_routines() {
+    
+#define ADD_ENTRY(name, rout) \
+    envt->add_binding(new SymObj(name), rout)
+
+    ADD_ENTRY("+", new BuiltinProcObj(builtin_plus, "+"));
+    ADD_ENTRY("-", new BuiltinProcObj(builtin_minus, "-"));
+    ADD_ENTRY("*", new BuiltinProcObj(builtin_times, "*"));
+    ADD_ENTRY("/", new BuiltinProcObj(builtin_div, "/"));
+    ADD_ENTRY(">", new BuiltinProcObj(builtin_gt, ">"));
+    ADD_ENTRY("<", new BuiltinProcObj(builtin_lt, "<"));
+    ADD_ENTRY("=", new BuiltinProcObj(builtin_arithmetic_eq, "="));
+    ADD_ENTRY("display", new BuiltinProcObj(builtin_display, "display"));
+    ADD_ENTRY("if", new SpecialOptIf());
+    ADD_ENTRY("lambda", new SpecialOptLambda());
+    ADD_ENTRY("define", new SpecialOptDefine());
+    ADD_ENTRY("set", new SpecialOptSet());
+}
+
+Evaluator::Evaluator() {
+    envt = new Environment();       // Top-level Environment
+    add_builtin_routines();
+}
+
+void push(Cons * &pc, FrameObj ** &top_ptr, Environment *envt) {
+    if (pc->car->is_simple_obj())           // Not an opt invocation
+    {
+        *top_ptr = envt->get_obj(pc->car);  // Objectify the symbol
+        dynamic_cast<EvalObj*>(*top_ptr)->prepare(pc);
+        top_ptr++;
+        pc = pc->next;                      // Move to the next instruction
+    }
+    else                                    // Operational Invocation
+    {
+        *top_ptr++ = new RetAddr(pc);       // Push the return address
+        pc = dynamic_cast<Cons*>(pc->car);  // Go deeper to enter the call
+    }
+}
+
+void stack_print(FrameObj **top_ptr) {
+    for (FrameObj **ptr = eval_stack; ptr != top_ptr; ptr++)
+        printf("%s\n", (*ptr)->_debug_repr().c_str());
+    puts("");
+}
+
+EvalObj *Evaluator::run_expr(Cons *prog) {
+    FrameObj **top_ptr = eval_stack;
+    Cons *pc = prog;
+    Continuation *cont = NULL;
+    // envt is this->envt
+    push(pc, top_ptr, envt);   
+    
+    while((*eval_stack)->is_ret_addr())
+    {
+        for (; pc && pc->skip; pc = pc->next);
+        if (pc)
+            push(pc, top_ptr, envt);
+        else
+        {
+            Cons *args = empty_list;
+            while (!(*(--top_ptr))->is_ret_addr())
+                args = new Cons(dynamic_cast<EvalObj*>(*top_ptr), args);
+            RetAddr *ret_addr = dynamic_cast<RetAddr*>(*top_ptr);
+            if (!ret_addr->addr)
+            {
+                Cons *nexp = cont->proc_body->cdr;
+                cont->proc_body = nexp;
+                if (nexp == empty_list)
+                {
+                    *top_ptr = args->car;
+                    envt = cont->envt;
+                    pc = cont->pc->next;
+                    cont = cont->prev_cont;
+                }
+                else pc = nexp;
+                top_ptr++;
+            }
+            else 
+                pc = dynamic_cast<OptObj*>(args->car)->call(args, envt, cont, top_ptr);
+        }
+    }
+    return dynamic_cast<EvalObj*>(*(eval_stack));
+}