diff --git a/src/assembler/asm.c b/src/assembler/asm.c
index 2d33f37e..a301b337 100644
--- a/src/assembler/asm.c
+++ b/src/assembler/asm.c
@@ -475,6 +475,18 @@ static uint32_t read_instruction(
     return instr;
 }
 
+/* Helper to get from a structure */
+static Dst dst_get(Dst ds, Dst key) {
+    switch (dst_type(ds)) {
+        default:
+            return dst_wrap_nil();
+        case DST_TABLE:
+            return dst_table_get(dst_unwrap_table(ds), key);
+        case DST_STRUCT:
+            return dst_struct_get(dst_unwrap_struct(ds), key);
+    }
+}
+
 /* Helper to assembly. Return the assembly result */
 static DstAssembleResult dst_asm1(DstAssembler *parent, Dst source, int flags) {
     DstAssembleResult result;
diff --git a/src/compiler/compile.c b/src/compiler/compile.c
index a24c43d9..1ed68c32 100644
--- a/src/compiler/compile.c
+++ b/src/compiler/compile.c
@@ -66,6 +66,19 @@ int dstc_iserr(DstFopts *opts) {
     return (opts->compiler->result.status == DST_COMPILE_ERROR);
 }
 
+/* Get the next key in an associative data structure. Used for iterating through an
+ * associative data structure. */
+const DstKV *dstc_next(Dst ds, const DstKV *kv) {
+    switch(dst_type(ds)) {
+        default:
+            return NULL;
+        case DST_TABLE:
+            return (const DstKV *) dst_table_next(dst_unwrap_table(ds), kv);
+        case DST_STRUCT:
+            return dst_struct_next(dst_unwrap_struct(ds), kv);
+    }
+}
+
 /* Allocate a slot index */
 int32_t dstc_lsloti(DstCompiler *c) {
     DstScope *scope = &dst_v_last(c->scopes);
@@ -257,22 +270,24 @@ DstSlot dstc_resolve(
 
     /* Symbol not found - check for global */
     {
-        Dst check = dst_table_get(c->env, dst_wrap_symbol(sym));
-        Dst ref;
-        if (!(dst_checktype(check, DST_STRUCT) || dst_checktype(check, DST_TABLE))) {
-            dstc_error(c, ast, dst_formatc("unknown symbol %q", sym));
-            return dstc_cslot(dst_wrap_nil());
-        }
-        ref = dst_get(check, dst_csymbolv(":ref"));
-        if (dst_checktype(ref, DST_ARRAY)) {
-            DstSlot ret = dstc_cslot(ref);
-            /* TODO save type info */
-            ret.flags |= DST_SLOT_REF | DST_SLOT_NAMED | DST_SLOT_MUTABLE | DST_SLOTTYPE_ANY;
-            ret.flags &= ~DST_SLOT_CONSTANT;
-            return ret;
-        } else {
-            Dst value = dst_get(check, dst_csymbolv(":value"));
-            return dstc_cslot(value);
+        Dst check;
+        DstBindingType btype = dst_env_resolve(c->env, sym, &check);
+        switch (btype) {
+            default:
+            case DST_BINDING_NONE:
+                dstc_error(c, ast, dst_formatc("unknown symbol %q", sym));
+                return dstc_cslot(dst_wrap_nil());
+            case DST_BINDING_DEF:
+            case DST_BINDING_MACRO: /* Macro should function like defs when not in calling pos */
+                return dstc_cslot(check);
+            case DST_BINDING_VAR:
+            {
+                DstSlot ret = dstc_cslot(check);
+                /* TODO save type info */
+                ret.flags |= DST_SLOT_REF | DST_SLOT_NAMED | DST_SLOT_MUTABLE | DST_SLOTTYPE_ANY;
+                ret.flags &= ~DST_SLOT_CONSTANT;
+                return ret;
+            }
         }
     }
 
@@ -627,7 +642,7 @@ DstSM *dstc_toslotskv(DstCompiler *c, Dst ds) {
     DstSM *ret = NULL;
     const DstKV *kv = NULL;
     DstFopts subopts = dstc_fopts_default(c);
-    while ((kv = dst_next(ds, kv))) {
+    while ((kv = dstc_next(ds, kv))) {
         DstSM km, vm;
         km.slot = dstc_value(subopts, kv->key);
         km.map = dst_ast_node(kv->key);
@@ -807,25 +822,22 @@ recur:
                     /* Symbols could be specials */
                     headval = dst_ast_unwrap1(tup[0]);
                     if (dst_checktype(headval, DST_SYMBOL)) {
-                        const DstSpecial *s = dstc_special(dst_unwrap_symbol(headval));
+                        const uint8_t *headsym = dst_unwrap_symbol(headval);
+                        const DstSpecial *s = dstc_special(headsym);
                         if (NULL != s) {
                             ret = s->compile(opts, ast, dst_tuple_length(tup) - 1, tup + 1);
                             compiled = 1;
                         } else {
                             /* Check macro */
-                            DstTable *env = c->env;
-                            Dst fn;
-                            Dst entry = dst_table_get(env, headval);
-                            for (;;) {
-                                if (dst_checktype(entry, DST_NIL)) break;
-                                if (dst_checktype(dst_get(entry, dst_csymbolv(":macro")), DST_NIL)) break;
-                                fn = dst_get(entry, dst_csymbolv(":value"));
-                                if (!dst_checktype(fn, DST_FUNCTION)) break;
+                            Dst macVal;
+                            DstBindingType btype = dst_env_resolve(c->env, headsym, &macVal);
+                            if (btype == DST_BINDING_MACRO &&
+                                    dst_checktype(macVal, DST_FUNCTION)) {
                                 if (macrorecur++ > DST_RECURSION_GUARD) {
                                     dstc_cerror(c, ast, "macro expansion recursed too deeply");
                                     return dstc_cslot(dst_wrap_nil());
                                 } else {
-                                    DstFunction *f = dst_unwrap_function(fn);
+                                    DstFunction *f = dst_unwrap_function(macVal);
                                     int lock = dst_gclock();
                                     DstSignal status = dst_call(f, dst_tuple_length(tup) - 1, tup + 1, &x);
                                     dst_gcunlock(lock);
@@ -843,6 +855,7 @@ recur:
                         /* Compile the head of the tuple */
                         subopts.flags = DST_FUNCTION | DST_CFUNCTION;
                         head = dstc_value(subopts, tup[0]);
+                        /* Add compile function call */
                         ret = dstc_call(opts, ast, dstc_toslots(c, tup + 1, dst_tuple_length(tup) - 1), head);
                     }
                 }
diff --git a/src/compiler/compile.h b/src/compiler/compile.h
index b912a757..fb5674c9 100644
--- a/src/compiler/compile.h
+++ b/src/compiler/compile.h
@@ -154,6 +154,9 @@ const DstSpecial *dstc_special(const uint8_t *name);
 /* Check error */
 int dstc_iserr(DstFopts *opts);
 
+/* Helper for iterating tables and structs */
+const DstKV *dstc_next(Dst ds, const DstKV *kv);
+
 /* Allocate a slot index */
 int32_t dstc_lsloti(DstCompiler *c);
 
diff --git a/src/compiler/specials.c b/src/compiler/specials.c
index 40f413b0..321b8636 100644
--- a/src/compiler/specials.c
+++ b/src/compiler/specials.c
@@ -65,10 +65,11 @@ static void destructure(DstCompiler *c, Dst left, DstSlot right,
         case DST_ARRAY:
             {
                 int32_t i, len, localright, localsub;
-                len = dst_length(left);
+                const Dst *values;
+                dst_seq_view(left, &values, &len);
                 for (i = 0; i < len; i++) {
                     DstSlot newright;
-                    Dst subval = dst_getindex(left, i);
+                    Dst subval = values[i];
                     localright = dstc_preread(c, ast, 0xFF, 1, right);
                     localsub = dstc_lslotn(c, 0xFF, 3);
                     if (i < 0x100) {
@@ -104,7 +105,7 @@ static void destructure(DstCompiler *c, Dst left, DstSlot right,
             {
                 int32_t localright, localsub;
                 const DstKV *kv = NULL;
-                while ((kv = dst_next(left, kv))) {
+                while ((kv = dstc_next(left, kv))) {
                     DstSlot newright;
                     DstSlot kslot = dstc_cslot(dst_ast_unwrap(kv->key));
                     Dst subval = kv->value;
diff --git a/src/compiler/stl.c b/src/compiler/stl.c
index f940af7e..0f2d5f6f 100644
--- a/src/compiler/stl.c
+++ b/src/compiler/stl.c
@@ -46,9 +46,6 @@ static const DstReg cfuns[] = {
     {"struct", dst_core_struct},
     {"buffer", dst_core_buffer},
     {"gensym", dst_core_gensym},
-    {"get", dst_core_get},
-    {"put", dst_core_put},
-    {"length", dst_core_length},
     {"gccollect", dst_core_gccollect},
     {"gcsetinterval", dst_core_gcsetinterval},
     {"gcinterval", dst_core_gcinterval},
@@ -100,6 +97,18 @@ DstTable *dst_stl_env(int flags) {
         DOP_RESUME | (1 << 24),
         DOP_RETURN
     };
+    static uint32_t get_asm[] = {
+        DOP_GET | (1 << 24),
+        DOP_RETURN
+    };
+    static uint32_t put_asm[] = {
+        DOP_PUT | (1 << 16) | (2 << 24),
+        DOP_RETURN
+    };
+    static uint32_t length_asm[] = {
+        DOP_LENGTH,
+        DOP_RETURN
+    };
 
     DstTable *env = dst_table(0);
     Dst ret = dst_wrap_table(env);
@@ -112,6 +121,9 @@ DstTable *dst_stl_env(int flags) {
     dst_env_def(env, "apply1", dst_wrap_function(dst_quick_asm("apply1", 2, 0, 2, apply_asm, sizeof(apply_asm))));
     dst_env_def(env, "yield", dst_wrap_function(dst_quick_asm("yield", 1, 0, 2, yield_asm, sizeof(yield_asm))));
     dst_env_def(env, "resume", dst_wrap_function(dst_quick_asm("resume", 2, 0, 2, resume_asm, sizeof(resume_asm))));
+    dst_env_def(env, "get", dst_wrap_function(dst_quick_asm("get", 2, 0, 2, get_asm, sizeof(get_asm))));
+    dst_env_def(env, "put", dst_wrap_function(dst_quick_asm("put", 3, 0, 3, put_asm, sizeof(put_asm))));
+    dst_env_def(env, "length", dst_wrap_function(dst_quick_asm("length", 1, 0, 1, length_asm, sizeof(length_asm))));
 
     dst_env_def(env, "VERSION", dst_cstringv(DST_VERSION));
 
diff --git a/src/core/corelib.c b/src/core/corelib.c
index 4e2dc9ef..96a8ea8e 100644
--- a/src/core/corelib.c
+++ b/src/core/corelib.c
@@ -180,37 +180,6 @@ int dst_core_gensym(DstArgs args) {
     }
 }
 
-int dst_core_length(DstArgs args) {
-    DST_FIXARITY(args, 1);
-    DST_RETURN_INTEGER(args, dst_length(args.v[0]));
-}
-
-int dst_core_get(DstArgs args) {
-    int32_t i;
-    Dst ds;
-    DST_MINARITY(args, 1);
-    ds = args.v[0];
-    for (i = 1; i < args.n; i++) {
-        ds = dst_get(ds, args.v[i]);
-        if (dst_checktype(ds, DST_NIL))
-            break;
-    }
-    DST_RETURN(args, ds);
-}
-
-int dst_core_put(DstArgs args) {
-    Dst ds, key, value;
-    DstArgs subargs = args;
-    DST_MINARITY(args, 3);
-    subargs.n -= 2;
-    if (dst_core_get(subargs)) return 1;
-    ds = *args.ret;
-    key = args.v[args.n - 2];
-    value = args.v[args.n - 1];
-    dst_put(ds, key, value);
-    return 0;
-}
-
 int dst_core_gccollect(DstArgs args) {
     (void) args;
     dst_collect();
@@ -252,13 +221,14 @@ int dst_core_next(DstArgs args) {
         kv = dst_checktype(args.v[1], DST_NIL)
             ? NULL
             : dst_table_find(t, args.v[1]);
+        kv = dst_table_next(t, kv);
     } else {
         const DstKV *st = dst_unwrap_struct(ds);
         kv = dst_checktype(args.v[1], DST_NIL)
             ? NULL
             : dst_struct_find(st, args.v[1]);
+        kv = dst_struct_next(st, kv);
     }
-    kv = dst_next(ds, kv);
     if (kv) {
         DST_RETURN(args, kv->key);
     }
diff --git a/src/core/util.c b/src/core/util.c
index 6b4152be..18ec7427 100644
--- a/src/core/util.c
+++ b/src/core/util.c
@@ -138,17 +138,27 @@ void dst_env_cfuns(DstTable *env, const DstReg *cfuns) {
     }
 }
 
-/* Resolve a symbol in the environment. Undefined symbols will
- * resolve to nil */
-Dst dst_env_resolve(DstTable *env, const char *name) {
+/* Resolve a symbol in the environment */
+DstBindingType dst_env_resolve(DstTable *env, const uint8_t *sym, Dst *out) {
     Dst ref;
-    Dst entry = dst_table_get(env, dst_csymbolv(name));
-    if (dst_checktype(entry, DST_NIL)) return dst_wrap_nil();
-    ref = dst_get(entry, dst_csymbolv(":ref"));
-    if (dst_checktype(ref, DST_ARRAY)) {
-        return dst_getindex(ref, 0);
+    DstTable *entry_table;
+    Dst entry = dst_table_get(env, dst_wrap_symbol(sym));
+    if (!dst_checktype(entry, DST_TABLE))
+        return DST_BINDING_NONE;
+    entry_table = dst_unwrap_table(entry);
+    if (!dst_checktype(
+        dst_table_get(entry_table, dst_csymbolv(":macro")),
+        DST_NIL)) {
+        *out = dst_table_get(entry_table, dst_csymbolv(":value"));
+        return DST_BINDING_MACRO;
     }
-    return dst_get(entry, dst_csymbolv(":value"));
+    ref = dst_table_get(entry_table, dst_csymbolv(":ref"));
+    if (dst_checktype(ref, DST_ARRAY)) {
+        *out = ref;
+        return DST_BINDING_VAR;
+    }
+    *out = dst_table_get(entry_table, dst_csymbolv(":value"));
+    return DST_BINDING_DEF;
 }
 
 /* Get module from the arguments passed to library */
diff --git a/src/core/value.c b/src/core/value.c
index da853190..b3a8437d 100644
--- a/src/core/value.c
+++ b/src/core/value.c
@@ -154,163 +154,3 @@ int dst_compare(Dst x, Dst y) {
     }
     return (dst_type(x) < dst_type(y)) ? -1 : 1;
 }
-
-/* Get a value out af an associated data structure. For invalid
- * data structure or invalid key, returns nil. */
-Dst dst_get(Dst ds, Dst key) {
-    switch (dst_type(ds)) {
-    case DST_ARRAY:
-        if (dst_checktype(key, DST_INTEGER) &&
-                dst_unwrap_integer(key) >= 0 &&
-                dst_unwrap_integer(key) < dst_unwrap_array(ds)->count)
-            return dst_unwrap_array(ds)->data[dst_unwrap_integer(key)];
-        break;
-    case DST_TUPLE:
-        if (dst_checktype(key, DST_INTEGER) &&
-                dst_unwrap_integer(key) >= 0 &&
-                dst_unwrap_integer(key) < dst_tuple_length(dst_unwrap_tuple(ds)))
-            return dst_unwrap_tuple(ds)[dst_unwrap_integer(key)];
-        break;
-    case DST_BUFFER:
-        if (dst_checktype(key, DST_INTEGER) &&
-                dst_unwrap_integer(key) >= 0 &&
-                dst_unwrap_integer(key) < dst_unwrap_buffer(ds)->count)
-            return dst_wrap_integer(dst_unwrap_buffer(ds)->data[dst_unwrap_integer(key)]);
-        break;
-    case DST_STRING:
-    case DST_SYMBOL:
-        if (dst_checktype(key, DST_INTEGER) &&
-                dst_unwrap_integer(key) >= 0 &&
-                dst_unwrap_integer(key) < dst_string_length(dst_unwrap_string(ds)))
-            return dst_wrap_integer(dst_unwrap_string(ds)[dst_unwrap_integer(key)]);
-        break;
-    case DST_STRUCT:
-        return dst_struct_get(dst_unwrap_struct(ds), key);
-    case DST_TABLE:
-        return dst_table_get(dst_unwrap_table(ds), key);
-    default:
-        break;
-    }
-    return dst_wrap_nil();
-}
-
-/* Set a value in an associative data structure. Returns possible
- * error message, and NULL if no error. */
-void dst_put(Dst ds, Dst key, Dst value) {
-    switch (dst_type(ds)) {
-    case DST_ARRAY:
-    {
-        int32_t index;
-        DstArray *array = dst_unwrap_array(ds);
-        if (!dst_checktype(key, DST_INTEGER) || dst_unwrap_integer(key) < 0)
-            return;
-        index = dst_unwrap_integer(key);
-        if (index == INT32_MAX) return;
-        if (index >= array->count) {
-            dst_array_setcount(array, index + 1);
-        }
-        array->data[index]= value;
-        return;
-    }
-    case DST_BUFFER:
-    {
-        int32_t index;
-        DstBuffer *buffer = dst_unwrap_buffer(ds);
-        if (!dst_checktype(key, DST_INTEGER) || dst_unwrap_integer(key) < 0)
-            return;
-        index = dst_unwrap_integer(key);
-        if (index == INT32_MAX) return;
-        if (!dst_checktype(value, DST_INTEGER))
-            return;
-        if (index >= buffer->count) {
-            dst_buffer_setcount(buffer, index + 1);
-        }
-        buffer->data[index] = (uint8_t) (dst_unwrap_integer(value) & 0xFF);
-        return;
-    }
-    case DST_TABLE:
-        dst_table_put(dst_unwrap_table(ds), key, value);
-        return;
-    default:
-        return;
-    }
-}
-
-/* Get the next key in an associative data structure. Used for iterating through an
- * associative data structure. */
-const DstKV *dst_next(Dst ds, const DstKV *kv) {
-    switch(dst_type(ds)) {
-        default:
-            return NULL;
-        case DST_TABLE:
-            return (const DstKV *) dst_table_next(dst_unwrap_table(ds), kv);
-        case DST_STRUCT:
-            return dst_struct_next(dst_unwrap_struct(ds), kv);
-    }
-}
-
-/* Get the length of an object. Returns errors for invalid types */
-int32_t dst_length(Dst x) {
-    switch (dst_type(x)) {
-        default:
-            return 0;
-        case DST_STRING:
-        case DST_SYMBOL:
-            return dst_string_length(dst_unwrap_string(x));
-        case DST_ARRAY:
-            return dst_unwrap_array(x)->count;
-        case DST_BUFFER:
-            return dst_unwrap_buffer(x)->count;
-        case DST_TUPLE:
-            return dst_tuple_length(dst_unwrap_tuple(x));
-        case DST_STRUCT:
-            return dst_struct_length(dst_unwrap_struct(x));
-        case DST_TABLE:
-            return dst_unwrap_table(x)->count;
-    }
-}
-
-/* Index into a data structure. Returns nil for out of bounds or invlalid data structure */
-Dst dst_getindex(Dst ds, int32_t index) {
-    switch (dst_type(ds)) {
-        default:
-            return dst_wrap_nil();
-        case DST_STRING:
-        case DST_SYMBOL:
-            if (index >= dst_string_length(dst_unwrap_string(ds))) return dst_wrap_nil();
-            return dst_wrap_integer(dst_unwrap_string(ds)[index]);
-        case DST_ARRAY:
-            if (index >= dst_unwrap_array(ds)->count) return dst_wrap_nil();
-            return dst_unwrap_array(ds)->data[index];
-        case DST_BUFFER:
-            if (index >= dst_unwrap_buffer(ds)->count) return dst_wrap_nil();
-            return dst_wrap_integer(dst_unwrap_buffer(ds)->data[index]);
-        case DST_TUPLE:
-            if (index >= dst_tuple_length(dst_unwrap_tuple(ds))) return dst_wrap_nil();
-            return dst_unwrap_tuple(ds)[index];
-    }
-}
-
-/* Set an index in a linear data structure. Does nothing if data structure
- * is invalid */
-void dst_setindex(Dst ds, Dst value, int32_t index) {
-    switch (dst_type(ds)) {
-        default:
-            return;
-        case DST_ARRAY:
-            if (index >= dst_unwrap_array(ds)->count) {
-                dst_array_ensure(dst_unwrap_array(ds), 2 * index);
-                dst_unwrap_array(ds)->count = index + 1;
-            }
-            dst_unwrap_array(ds)->data[index] = value;
-            return;
-        case DST_BUFFER:
-            if (!dst_checktype(value, DST_INTEGER)) return;
-            if (index >= dst_unwrap_buffer(ds)->count) {
-                dst_buffer_ensure(dst_unwrap_buffer(ds), 2 * index);
-                dst_unwrap_buffer(ds)->count = index + 1;
-            }
-            dst_unwrap_buffer(ds)->data[index] = dst_unwrap_integer(value);
-            return;
-    }
-}
diff --git a/src/core/vm.c b/src/core/vm.c
index fbb97857..dcb5e18a 100644
--- a/src/core/vm.c
+++ b/src/core/vm.c
@@ -769,37 +769,241 @@ static void *op_lookup[255] = {
     }
 
     VM_OP(DOP_PUT)
-    dst_put(stack[oparg(1, 0xFF)],
-            stack[oparg(2, 0xFF)],
-            stack[oparg(3, 0xFF)]);
-    ++pc;
-    vm_checkgc_next();
+    {
+        Dst ds = stack[oparg(1, 0xFF)];
+        Dst key = stack[oparg(2, 0xFF)];
+        Dst value = stack[oparg(3, 0xFF)];
+        switch (dst_type(ds)) {
+            default:
+                vm_throw("expected mutable data structure");
+            case DST_ARRAY:
+            {
+                int32_t index;
+                DstArray *array = dst_unwrap_array(ds);
+                if (!dst_checktype(key, DST_INTEGER) || dst_unwrap_integer(key) < 0)
+                    vm_throw("expected non-negative integer key");
+                index = dst_unwrap_integer(key);
+                if (index == INT32_MAX)
+                    vm_throw("key too large");
+                if (index >= array->count) {
+                    dst_array_setcount(array, index + 1);
+                }
+                array->data[index] = value;
+                break;
+            }
+            case DST_BUFFER:
+            {
+                int32_t index;
+                DstBuffer *buffer = dst_unwrap_buffer(ds);
+                if (!dst_checktype(key, DST_INTEGER) || dst_unwrap_integer(key) < 0)
+                    vm_throw("expected non-negative integer key");
+                index = dst_unwrap_integer(key);
+                if (index == INT32_MAX)
+                    vm_throw("key too large");
+                if (!dst_checktype(value, DST_INTEGER))
+                    vm_throw("expected integer value");
+                if (index >= buffer->count) {
+                    dst_buffer_setcount(buffer, index + 1);
+                }
+                buffer->data[index] = (uint8_t) (dst_unwrap_integer(value) & 0xFF);
+                break;
+            }
+            case DST_TABLE:
+                dst_table_put(dst_unwrap_table(ds), key, value);
+                break;
+        }
+        ++pc;
+        vm_checkgc_next();
+    }
 
     VM_OP(DOP_PUT_INDEX)
-    dst_setindex(stack[oparg(1, 0xFF)],
-            stack[oparg(2, 0xFF)],
-            oparg(3, 0xFF));
-    ++pc;
-    vm_checkgc_next();
+    {
+        Dst ds = stack[oparg(1, 0xFF)];
+        Dst value = stack[oparg(2, 0xFF)];
+        int32_t index = oparg(3, 0xFF);
+        switch (dst_type(ds)) {
+            default:
+                vm_throw("expected mutable indexed data structure");
+            case DST_ARRAY:
+                if (index >= dst_unwrap_array(ds)->count) {
+                    dst_array_ensure(dst_unwrap_array(ds), 2 * index);
+                    dst_unwrap_array(ds)->count = index + 1;
+                }
+                dst_unwrap_array(ds)->data[index] = value;
+                break;
+            case DST_BUFFER:
+                if (!dst_checktype(value, DST_INTEGER))\
+                    vm_throw("expected integer to set in buffer");
+                if (index >= dst_unwrap_buffer(ds)->count) {
+                    dst_buffer_ensure(dst_unwrap_buffer(ds), 2 * index);
+                    dst_unwrap_buffer(ds)->count = index + 1;
+                }
+                dst_unwrap_buffer(ds)->data[index] = dst_unwrap_integer(value);
+                break;
+        }
+        ++pc;
+        vm_checkgc_next();
+    }
 
     VM_OP(DOP_GET)
-    stack[oparg(1, 0xFF)] = dst_get(
-            stack[oparg(2, 0xFF)],
-            stack[oparg(3, 0xFF)]);
-    ++pc;
-    vm_next();
+    {
+        Dst ds = stack[oparg(2, 0xFF)];
+        Dst key = stack[oparg(3, 0xFF)];
+        Dst value;
+        switch (dst_type(ds)) {
+            default:
+                vm_throw("expected data structure");
+            case DST_STRUCT:
+                value = dst_struct_get(dst_unwrap_struct(ds), key);
+                break;
+            case DST_TABLE:
+                value = dst_table_get(dst_unwrap_table(ds), key);
+                break;
+            case DST_ARRAY:
+                {
+                    DstArray *array = dst_unwrap_array(ds);
+                    int32_t index;
+                    if (!dst_checktype(key, DST_INTEGER))
+                        vm_throw("expected integer key");
+                    index = dst_unwrap_integer(key);
+                    if (index < 0 || index >= array->count) {
+                        /*vm_throw("index out of bounds");*/
+                        value = dst_wrap_nil();
+                    } else {
+                        value = array->data[index];
+                    }
+                    break;
+                }
+            case DST_TUPLE:
+                {
+                    const Dst *tuple = dst_unwrap_tuple(ds);
+                    int32_t index;
+                    if (!dst_checktype(key, DST_INTEGER))
+                        vm_throw("expected integer key");
+                    index = dst_unwrap_integer(key);
+                    if (index < 0 || index >= dst_tuple_length(tuple)) {
+                        /*vm_throw("index out of bounds");*/
+                        value = dst_wrap_nil();
+                    } else {
+                        value = tuple[index];
+                    }
+                    break;
+                }
+            case DST_BUFFER:
+                {
+                    DstBuffer *buffer = dst_unwrap_buffer(ds);
+                    int32_t index;
+                    if (!dst_checktype(key, DST_INTEGER))
+                        vm_throw("expected integer key");
+                    index = dst_unwrap_integer(key);
+                    if (index < 0 || index >= buffer->count) {
+                        /*vm_throw("index out of bounds");*/
+                        value = dst_wrap_nil();
+                    } else {
+                        value = dst_wrap_integer(buffer->data[index]);
+                    }
+                    break;
+                }
+            case DST_STRING:
+            case DST_SYMBOL:
+                {
+                    const uint8_t *str = dst_unwrap_string(ds);
+                    int32_t index;
+                    if (!dst_checktype(key, DST_INTEGER))
+                        vm_throw("expected integer key");
+                    index = dst_unwrap_integer(key);
+                    if (index < 0 || index >= dst_string_length(str)) {
+                        /*vm_throw("index out of bounds");*/
+                        value = dst_wrap_nil();
+                    } else {
+                        value = dst_wrap_integer(str[index]);
+                    }
+                    break;
+                }
+        }
+        stack[oparg(1, 0xFF)] = value;
+        ++pc;
+        vm_next();
+    }
 
     VM_OP(DOP_GET_INDEX)
-    stack[oparg(1, 0xFF)] = dst_getindex(
-            stack[oparg(2, 0xFF)],
-            oparg(3, 0xFF));
-    ++pc;
-    vm_next();
+    {
+        Dst ds = stack[oparg(2, 0xFF)];
+        int32_t index = oparg(3, 0xFF);
+        Dst value;
+        switch (dst_type(ds)) {
+            default:
+                vm_throw("expected indexed data structure");
+            case DST_STRING:
+            case DST_SYMBOL:
+                if (index >= dst_string_length(dst_unwrap_string(ds))) {
+                    /*vm_throw("index out of bounds");*/
+                    value = dst_wrap_nil();
+                } else {
+                    value = dst_wrap_integer(dst_unwrap_string(ds)[index]);
+                }
+                break;
+            case DST_ARRAY:
+                if (index >= dst_unwrap_array(ds)->count) {
+                    /*vm_throw("index out of bounds");*/
+                    value = dst_wrap_nil();
+                } else {
+                    value = dst_unwrap_array(ds)->data[index];
+                }
+                break;
+            case DST_BUFFER:
+                if (index >= dst_unwrap_buffer(ds)->count) {
+                    /*vm_throw("index out of bounds");*/
+                    value = dst_wrap_nil();
+                } else {
+                    value = dst_wrap_integer(dst_unwrap_buffer(ds)->data[index]);
+                }
+                break;
+            case DST_TUPLE:
+                if (index >= dst_tuple_length(dst_unwrap_tuple(ds))) {
+                    /*vm_throw("index out of bounds");*/
+                    value = dst_wrap_nil();
+                } else {
+                    value = dst_unwrap_tuple(ds)[index];
+                }
+                break;
+        }
+        stack[oparg(1, 0xFF)] = value;
+        ++pc;
+        vm_next();
+    }
 
     VM_OP(DOP_LENGTH)
-    stack[oparg(1, 0xFF)] = dst_wrap_integer(dst_length(stack[oparg(2, 0xFFFF)]));
-    ++pc;
-    vm_next();
+    {
+        Dst x = stack[oparg(2, 0xFFFF)];
+        int32_t len;
+        switch (dst_type(x)) {
+            default:
+                vm_throw("expected data structure");
+            case DST_STRING:
+            case DST_SYMBOL:
+                len = dst_string_length(dst_unwrap_string(x));
+                break;
+            case DST_ARRAY:
+                len = dst_unwrap_array(x)->count;
+                break;
+            case DST_BUFFER:
+                len = dst_unwrap_buffer(x)->count;
+                break;
+            case DST_TUPLE:
+                len = dst_tuple_length(dst_unwrap_tuple(x));
+                break;
+            case DST_STRUCT:
+                len = dst_struct_length(dst_unwrap_struct(x));
+                break;
+            case DST_TABLE:
+                len = dst_unwrap_table(x)->count;
+                break;
+        }
+        stack[oparg(1, 0xFF)] = dst_wrap_integer(len);
+        ++pc;
+        vm_next();
+    }
 
     /* Return from c function. Simpler than returning from dst function */
     vm_return_cfunc:
@@ -808,7 +1012,7 @@ static void *op_lookup[255] = {
         if (fiber->frame == 0) goto vm_exit;
         stack = fiber->data + fiber->frame;
         stack[oparg(1, 0xFF)] = retreg;
-        pc++;
+        ++pc;
         vm_checkgc_next();
     }
 
diff --git a/src/include/dst/dst.h b/src/include/dst/dst.h
index f413b870..9d2f557b 100644
--- a/src/include/dst/dst.h
+++ b/src/include/dst/dst.h
@@ -173,12 +173,6 @@ int dst_verify(DstFuncDef *def);
 int dst_equals(Dst x, Dst y);
 int32_t dst_hash(Dst x);
 int dst_compare(Dst x, Dst y);
-Dst dst_get(Dst ds, Dst key);
-void dst_put(Dst ds, Dst key, Dst value);
-const DstKV *dst_next(Dst ds, const DstKV *kv);
-int32_t dst_length(Dst x);
-Dst dst_getindex(Dst ds, int32_t index);
-void dst_setindex(Dst ds, Dst value, int32_t index);
 int dst_cstrcmp(const uint8_t *str, const char *other);
 
 /* VM functions */
@@ -189,10 +183,16 @@ DstSignal dst_continue(DstFiber *fiber, Dst in, Dst *out);
 DstSignal dst_call(DstFunction *fun, int32_t argn, const Dst *argv, Dst *out);
 
 /* Env helpers */
+typedef enum {
+    DST_BINDING_NONE,
+    DST_BINDING_DEF,
+    DST_BINDING_VAR,
+    DST_BINDING_MACRO
+} DstBindingType;
 void dst_env_def(DstTable *env, const char *name, Dst val);
 void dst_env_var(DstTable *env, const char *name, Dst val);
 void dst_env_cfuns(DstTable *env, const DstReg *cfuns);
-Dst dst_env_resolve(DstTable *env, const char *name);
+DstBindingType dst_env_resolve(DstTable *env, const uint8_t *sym, Dst *out);
 DstTable *dst_env_arg(DstArgs args);
 
 /* STL */
diff --git a/src/include/dst/dstcorelib.h b/src/include/dst/dstcorelib.h
index 99e3ebc3..d71dc271 100644
--- a/src/include/dst/dstcorelib.h
+++ b/src/include/dst/dstcorelib.h
@@ -80,9 +80,6 @@ int dst_core_table(DstArgs args);
 int dst_core_struct(DstArgs args);
 int dst_core_buffer(DstArgs args);
 int dst_core_gensym(DstArgs args);
-int dst_core_length(DstArgs args);
-int dst_core_get(DstArgs args);
-int dst_core_put(DstArgs args);
 int dst_core_type(DstArgs args);
 int dst_core_next(DstArgs args);
 int dst_core_hash(DstArgs args);