pit: VM-style evaluation

2 files changed, 260 insertions, 52 deletions

diff --git a/pit/src/runtime/eval.c b/pit/src/runtime/eval.c
index 44c9a57..1822bc5 100644
--- a/pit/src/runtime/eval.c
+++ b/pit/src/runtime/eval.c
@@ -1,10 +1,39 @@
 #include <lcq/pit/runtime/eval.h>
 
-pit_value pit_eval(pit_runtime *rt, pit_value top) {
+#include <stdio.h>
+
+void pit_vm_call_special_form(pit_runtime *rt, pit_value f, pit_value args) {
+    char buf[256] = {0};
+    switch (pit_value_sort(f)) {
+    case PIT_VALUE_SORT_REF: {
+        pit_value_heavy *h = pit_value_ref_deref(rt, pit_value_as_ref(rt, f));
+        if (!h) { pit_error(rt, "bad ref for special form"); return; }
+        switch (h->hsort) {
+        case PIT_VALUE_HEAVY_SORT_NATIVEFUNC:
+            h->in.nativefunc.f(rt, args, h->in.nativefunc.data);
+            break;
+        default: {
+            i64 end = pit_dump(rt, buf, sizeof(buf) - 1, f, true);
+            buf[end] = 0;
+            pit_error(rt, "attempted to apply non-nativefunc special form: %s", buf);
+            return;
+        }
+        }
+        break;
+    }
+    default: {
+        i64 end = pit_dump(rt, buf, sizeof(buf) - 1, f, true);
+        buf[end] = 0;
+        pit_error(rt, "attempted to apply non-function special form: %s", buf);
+        return;
+    }
+    }
+}
+
+pit_value pit_vm_compile(pit_runtime *rt, pit_value top) {
+    pit_value ret = PIT_NIL;
     i64 expr_stack_reset = rt->expr_stack->next;
-    i64 result_stack_reset = rt->result_stack->next;
     i64 traversal_reset = rt->traversal->next;
-    // pit_vec_reset(pit_annotated_ref)(rt->backtrace);
     if (pit_vec_push(pit_value)(rt->expr_stack, top) < 0)
         pit_error(rt, "evaluation stack overflow");
     /* first, convert the expression tree into "polish notation" in traversal */
@@ -13,22 +42,17 @@ pit_value pit_eval(pit_runtime *rt, pit_value top) {
         if (rt->error != PIT_NIL) goto end;
         if (pit_vec_pop(pit_value)(rt->expr_stack, &cur) < 0)
             pit_error(rt, "evaluation stack underflow");
-        if (pit_value_is_cons(rt, cur)) { /* compound expressions: function/macro application special forms */
+        fprintf(stderr, "cur: "); pit_dump_to_file(rt, stderr, cur, false); fprintf(stderr, "\n");
+        if (pit_value_is_cons(rt, cur)) {
             pit_value fsym = pit_value_cons_car(rt, cur);
             bool is_symbol = pit_value_is_symbol(rt, fsym);
             pit_annotation *ann = pit_annotation_get(rt, pit_value_as_ref(rt, cur));
             if (is_symbol && pit_symtab_is_symbol_special_form(rt, fsym)) { /* special forms */
                 pit_value f = pit_symtab_fget(rt, fsym);
                 pit_value args = pit_value_cons_cdr(rt, cur);
-                /* special forms are nativefuncs that directly manipulate the stacks
-                   basically macros, but we don't need to evaluate the return value */
-                pit_value_apply(rt, f, args);
+                pit_vm_call_special_form(rt, f, args);
             } else if (is_symbol && pit_symtab_is_symbol_macro(rt, fsym)) { /* macros */
-                pit_value f = pit_symtab_fget(rt, fsym);
-                pit_value args = pit_value_cons_cdr(rt, cur);
-                pit_value res = pit_value_apply(rt, f, args);
-                if (pit_vec_push(pit_value)(rt->expr_stack, res) < 0)
-                    pit_error(rt, "evaluation stack overflow");
+                pit_error(rt, "encountered a macro while evaluating");
             } else { /* normal functions */
                 pit_value args = pit_value_cons_cdr(rt, cur);
                 i64 argcount = 0;
@@ -42,69 +66,250 @@ pit_value pit_eval(pit_runtime *rt, pit_value top) {
                     if (pit_vec_push(pit_value)(rt->expr_stack, fsym) < 0)
                         pit_error(rt, "evaluation stack overflow");
                 }
-                pit_traversal_push_application(rt, rt->traversal, argcount, ann);
+                pit_traversal_push_value(rt, rt->traversal,
+                    pit_value_list(rt, 2, pit_symtab_intern_cstr(rt, "apply"), pit_value_integer_new(rt, argcount))
+                );
                 if (is_symbol) {
-                    pit_value f = pit_symtab_fget(rt, fsym);
-                    pit_traversal_push_value(rt, rt->traversal, f);
+                    pit_traversal_push_value(rt, rt->traversal,
+                        pit_value_list(rt, 1, pit_symtab_intern_cstr(rt, "fget"))
+                    );
+                    pit_traversal_push_value(rt, rt->traversal,
+                        pit_value_list(rt, 2, pit_symtab_intern_cstr(rt, "literal"), fsym)
+                    );
                 }
             }
         } else if (pit_value_is_symbol(rt, cur)) { /* unquoted symbols: variable lookup */
             pit_symtab_entry *ent = pit_symtab_lookup(rt, cur);
             if (ent->is_keyword) {
-                pit_traversal_push_value(rt, rt->traversal, cur);
+                pit_traversal_push_value(rt, rt->traversal,
+                    pit_value_list(rt, 2, pit_symtab_intern_cstr(rt, "literal"), cur)
+                );
             } else {
-                pit_traversal_push_value(rt, rt->traversal, pit_symtab_get(rt, cur));
+                pit_traversal_push_value(rt, rt->traversal,
+                    pit_value_list(rt, 1, pit_symtab_intern_cstr(rt, "get"))
+                );
+                pit_traversal_push_value(rt, rt->traversal,
+                    pit_value_list(rt, 2, pit_symtab_intern_cstr(rt, "literal"), cur)
+                );
             }
         } else { /* other expressions evaluate to themselves! */
-            pit_traversal_push_value(rt, rt->traversal, cur);
+            pit_traversal_push_value(rt, rt->traversal,
+                pit_value_list(rt, 2, pit_symtab_intern_cstr(rt, "literal"), cur)
+            );
         }
     }
-    /* then, execute the polish notation traversal from right to left
-       this has the nice consequence of putting the arguments in the right order */
-    for (i64 idx = rt->traversal->next - 1; idx >= traversal_reset; --idx) {
+    for (i64 idx = traversal_reset; idx < rt->traversal->next; idx++) {
         pit_traversal_entry *ent = pit_vec_get(pit_traversal_entry)(rt->traversal, idx);
         if (ent == NULL) pit_error(rt, "evaluation traversal invalid");
         if (rt->error != PIT_NIL) goto end;
         switch (ent->sort) {
-        case PIT_TRAVERSAL_ENTRY_VALUE:
-            if (pit_vec_push(pit_value)(rt->result_stack, ent->in.value) < 0)
-                pit_error(rt, "evaluation result stack overflow");
-            break;
-        case PIT_TRAVERSAL_ENTRY_APPLICATION: {
-            pit_value f = PIT_NIL;
-            pit_value args = PIT_NIL;
-            if (pit_vec_pop(pit_value)(rt->result_stack, &f) < 0)
-                pit_error(rt, "evaluation result stack underflow");
-            for (i64 i = 0; i < ent->in.application.arity; ++i) {
-                pit_value a = PIT_NIL;
-                if (pit_vec_pop(pit_value)(rt->result_stack, &a) < 0)
-                    pit_error(rt, "evaluation result stack underflow");
-                args = pit_value_cons(rt, a, args);
-            }
-            if (ent->in.application.annotation != NULL) {
-                pit_backtrace_entry be;
-                be.val = f;
-                be.ann = *ent->in.application.annotation;
-                rt->source_line = ent->in.application.annotation->line;
-                rt->source_column = ent->in.application.annotation->column;
-                pit_vec_push(pit_backtrace_entry)(rt->backtrace, be);
-            }
-            if (pit_vec_push(pit_value)(rt->result_stack, pit_value_apply(rt, f, args)) < 0)
-                pit_error(rt, "evaluation result stack underflow");
+        case PIT_TRAVERSAL_ENTRY_VALUE: {
+            ret = pit_value_cons(rt, ent->in.value, ret);
             break;
         }
         default:
             pit_error(rt, "unknown traversal entry");
+            ret = PIT_NIL;
             goto end;
         }
     }
 end: {
-        pit_value ret = PIT_NIL;
-        if (pit_vec_pop(pit_value)(rt->result_stack, &ret) < 0)
-            pit_error(rt, "evaluation result stack underflow");
         rt->expr_stack->next = expr_stack_reset;
-        rt->result_stack->next = result_stack_reset;
         rt->traversal->next = traversal_reset;
+        fprintf(stderr, "compiled: "); pit_dump_to_file(rt, stderr, ret, false); fprintf(stderr, "\n");
         return ret;
     }
 }
+
+/* add a new stack frame to the vm (with a tag and callsite annotation) */
+void pit_vm_push_code_func(pit_runtime *rt, pit_value code, pit_value tag, pit_annotation ann, pit_value bound) {
+    pit_callstack_entry ent;
+    ent.tag = tag;
+    ent.ann = ann;
+    ent.code = code;
+    ent.bound = bound;
+    fprintf(stderr, "push code: "); pit_dump_to_file(rt, stderr, code, false); fprintf(stderr, "\n");
+    if (pit_vec_push(pit_callstack_entry)(rt->callstack, ent) < 0) {
+        pit_error(rt, "call stack overflow");
+    }
+}
+
+/* add a new stack frame to the vm (with no annotation) */
+void pit_vm_push_code(pit_runtime *rt, pit_value code) {
+    pit_annotation ann;
+    ann.line = -1;
+    ann.column = -1;
+    pit_vm_push_code_func(rt, code, PIT_NIL, ann, PIT_NIL);
+}
+
+void pit_vm_push(pit_runtime *rt, pit_value v) {
+    fprintf(stderr, "push: "); pit_dump_to_file(rt, stderr, v, false); fprintf(stderr, "\n");
+    if (pit_vec_push(pit_value)(rt->result_stack, v) < 0) {
+        pit_error(rt, "vm stack overflow");
+    }
+}
+
+pit_value pit_vm_pop(pit_runtime *rt) {
+    pit_value ret = PIT_NIL;
+    if (pit_vec_pop(pit_value)(rt->result_stack, &ret) < 0) {
+        pit_error(rt, "vm stack underflow");
+    }
+    fprintf(stderr, "pop: "); pit_dump_to_file(rt, stderr, ret, false); fprintf(stderr, "\n");
+    return ret;
+}
+
+void pit_vm_call_lisp(pit_runtime *rt, pit_value tag, pit_value closure, pit_value args) {
+    pit_value bound = PIT_NIL;
+    pit_value env = pit_value_array_get(rt, closure, 0);
+    pit_value anames = pit_value_array_get(rt, closure, 1);
+    pit_value arg_rest_nm = pit_value_array_get(rt, closure, 2);
+    pit_value body = pit_value_array_get(rt, closure, 3);
+    if (rt->error != PIT_NIL) return;
+    while (env != PIT_NIL) { /* first, bind all entries in the closure */
+        pit_value b = pit_value_cons_car(rt, env);
+        pit_value nm = pit_value_cons_car(rt, b);
+        pit_symtab_bind(rt, nm, pit_value_cons_cdr(rt, b));
+        bound = pit_value_cons(rt, nm, bound);
+        env = pit_value_cons_cdr(rt, env);
+    }
+    while (anames != PIT_NIL) { /* bind all argument names to their values */
+        pit_value nm = pit_value_cons_car(rt, anames);
+        pit_value cell = pit_value_cell_new(rt, PIT_NIL);
+        if (arg_rest_nm != PIT_NIL && pit_value_eq(nm, arg_rest_nm)) {
+            pit_value_cell_set(rt, cell, args, nm);
+            pit_symtab_bind(rt, nm, cell);
+            break;
+        } else {
+            pit_value_cell_set(rt, cell, pit_value_cons_car(rt, args), nm);
+            pit_symtab_bind(rt, nm, cell);
+        }
+        bound = pit_value_cons(rt, nm, bound);
+        args = pit_value_cons_cdr(rt, args);
+        anames = pit_value_cons_cdr(rt, anames);
+    }
+    pit_annotation ann;
+    ann.line = -1;
+    ann.column = -1;
+    pit_vm_push_code_func(rt, body, tag, ann, bound);
+}
+
+void pit_vm_call(pit_runtime *rt, pit_value f, pit_value args) {
+    char buf[256] = {0};
+    if (pit_value_is_symbol(rt, f)) f = pit_symtab_fget(rt, f);
+    switch (pit_value_sort(f)) {
+    case PIT_VALUE_SORT_REF: {
+        pit_value_heavy *h = pit_value_ref_deref(rt, pit_value_as_ref(rt, f));
+        if (!h) { pit_error(rt, "bad ref for function"); return; }
+        switch (h->hsort) {
+        case PIT_VALUE_HEAVY_SORT_NATIVEFUNC:
+            pit_vm_push(rt, h->in.nativefunc.f(rt, args, h->in.nativefunc.data));
+            break;
+        case PIT_VALUE_HEAVY_SORT_FUNC:
+            pit_vm_call_lisp(rt, h->in.func.nm, h->in.func.closure, args);
+            break;
+        default: {
+            i64 end = pit_dump(rt, buf, sizeof(buf) - 1, f, true);
+            buf[end] = 0;
+            pit_error(rt, "attempted to apply non-function ref: %s", buf);
+            return;
+        }
+        }
+        break;
+    }
+    default: {
+        i64 end = pit_dump(rt, buf, sizeof(buf) - 1, f, true);
+        buf[end] = 0;
+        pit_error(rt, "attempted to apply non-function value: %s", buf);
+        return;
+    }
+    }
+}
+
+/* run one instruction of the VM */
+bool pit_vm_run_one(pit_runtime *rt) {
+    char buf[256] = {0};
+    if (rt->callstack->next < 1) return false;
+    pit_callstack_entry *ent = pit_vec_get(pit_callstack_entry)(rt->callstack, rt->callstack->next - 1);
+    if (ent == NULL) {
+        pit_error(rt, "malformed call stack");
+        return false;
+    }
+    pit_value ins = pit_value_cons_car(rt, ent->code);
+    if (ins == PIT_NIL) {
+        pit_error(rt, "malformed vm instruction");
+        return false;
+    }
+    pit_value bound = ent->bound;
+    pit_value rest = pit_value_cons_cdr(rt, ent->code);
+    bool final = false;
+    if (rest == PIT_NIL) {
+        final = true;
+        pit_vec_pop(pit_callstack_entry)(rt->callstack, NULL);
+    } else ent->code = rest;
+    fprintf(stderr, "ins: "); pit_dump_to_file(rt, stderr, ins, false); fprintf(stderr, "\n");
+    pit_value op = pit_value_cons_car(rt, ins);
+    if (pit_symtab_symbol_name_match_cstr(rt, op, "literal")) {
+        pit_vm_push(rt, pit_value_cons_car(rt, pit_value_cons_cdr(rt, ins)));
+    } else if (pit_symtab_symbol_name_match_cstr(rt, op, "get")) {
+        pit_vm_push(rt, pit_symtab_get(rt, pit_vm_pop(rt)));
+    } else if (pit_symtab_symbol_name_match_cstr(rt, op, "fget")) {
+        pit_vm_push(rt, pit_symtab_fget(rt, pit_vm_pop(rt)));
+    } else if (pit_symtab_symbol_name_match_cstr(rt, op, "apply")) {
+        i64 arity = pit_value_as_integer(rt, pit_value_cons_car(rt, pit_value_cons_cdr(rt, ins)));
+        pit_value f = pit_vm_pop(rt);
+        pit_value args = PIT_NIL;
+        while (arity-- > 0) args = pit_value_cons(rt, pit_vm_pop(rt), args);
+        if (pit_value_is_symbol(rt, f)) f = pit_symtab_fget(rt, f);
+        switch (pit_value_sort(f)) {
+        case PIT_VALUE_SORT_REF: {
+            pit_value_heavy *h = pit_value_ref_deref(rt, pit_value_as_ref(rt, f));
+            if (!h) { pit_error(rt, "bad ref for function"); return PIT_NIL; }
+            switch (h->hsort) {
+            case PIT_VALUE_HEAVY_SORT_NATIVEFUNC:
+                pit_vm_push(rt, h->in.nativefunc.f(rt, args, h->in.nativefunc.data));
+                break;
+            case PIT_VALUE_HEAVY_SORT_FUNC:
+                pit_vm_call_lisp(rt, h->in.func.nm, h->in.func.closure, args);
+                break;
+            default: {
+                i64 end = pit_dump(rt, buf, sizeof(buf) - 1, f, true);
+                buf[end] = 0;
+                pit_error(rt, "attempted to apply non-function ref: %s", buf);
+                return false;
+            }
+            }
+            break;
+        }
+        default: {
+            i64 end = pit_dump(rt, buf, sizeof(buf) - 1, f, true);
+            buf[end] = 0;
+            pit_error(rt, "attempted to apply non-function value: %s", buf);
+            return false;
+        }
+        }
+    } else {
+        pit_error(rt, "unknown vm operation");
+        return false;
+    }
+    if (final) { /* if we have finished this stack frame */
+        fprintf(stderr, "unbinding: "); pit_dump_to_file(rt, stderr, bound, false); fprintf(stderr, "\n");
+        while (bound != PIT_NIL) { /* unbind everything we bound for the frame, in reverse */
+            pit_symtab_unbind(rt, pit_value_cons_car(rt, bound));
+            bound = pit_value_cons_cdr(rt, bound);
+        }
+    }
+    return true;
+}
+
+/* run the VM until evaluation finishes, returning the result */
+pit_value pit_vm_eval(pit_runtime *rt, pit_value v) {
+    pit_vm_push_code(rt, v);
+    while (pit_vm_run_one(rt));
+    pit_vm_pop(rt);
+}
+
+pit_value pit_vm_apply(pit_runtime *rt, pit_value f, pit_value args) {
+    pit_vm_call(rt, f, args);
+    while (pit_vm_run_one(rt));
+    pit_vm_pop(rt);
+}
diff --git a/pit/src/runtime/value/func.c b/pit/src/runtime/value/func.c
index 3843553..5f88cb0 100644
--- a/pit/src/runtime/value/func.c
+++ b/pit/src/runtime/value/func.c
@@ -94,7 +94,8 @@ pit_value pit_value_func_lambda(pit_runtime *rt, pit_value args, pit_value body)
         }
     }
     arg_cells = pit_value_list_reverse(rt, arg_cells);
-    pit_value closure[4] = {env, arg_cells, arg_rest_nm, expanded};
+    pit_value compiled = pit_vm_compile(rt, expanded);
+    pit_value closure[4] = {env, arg_cells, arg_rest_nm, compiled};
     h->in.func.nm = PIT_NIL;
     h->in.func.closure = pit_value_array_from_buf(rt, closure, 4);
     return ret;
@@ -153,7 +154,9 @@ pit_value pit_value_apply(pit_runtime *rt, pit_value f, pit_value args) {
                 args = pit_value_cons_cdr(rt, args);
                 anames = pit_value_cons_cdr(rt, anames);
             }
-            pit_value ret = pit_eval(rt, body); /* evaluate the body */
+            /* TODO */ 
+            pit_value ret = body;
+            // pit_value ret = pit_eval(rt, body); /* evaluate the body */
             while (bound != PIT_NIL) { /* unbind everything we bound earlier, in reverse */
                 pit_symtab_unbind(rt, pit_value_cons_car(rt, bound));
                 bound = pit_value_cons_cdr(rt, bound);