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-rw-r--r--eval.cpp91
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));
+}