diff --git a/wai.c b/wai.c
index aac65ca..48f897f 100644
--- a/wai.c
+++ b/wai.c
@@ -27,6 +27,7 @@
 #include <stddef.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <sys/stat.h>
 #include <inttypes.h>
 
@@ -48,8 +49,8 @@ enum section {
 
 #define STACK_CAPACITY 1024
 struct stack {
-  double items[STACK_CAPACITY];
-  size_t count;
+  u_char items[STACK_CAPACITY];
+  size_t bytes;
 };
 
 #define MAX_FUNCTIONS 128
@@ -87,7 +88,6 @@ enum INSTRUCTION {
   INSTR_CALL = 0x10,
   INSTR_ELSE = 0x05,
   INSTR_END = 0x0b,
-  INSTR_F64 = 0x7C,
   INSTR_F64_CONST = 0x44,
   INSTR_F64_LT = 0x63,
   INSTR_F64_MUL = 0xa2,
@@ -106,26 +106,81 @@ enum TYPE {
   TYPE_EXTERNREF = 0x6F
 };
 
+static const int TYPE_SIZE[] = {
+  [TYPE_I32] = 4,
+  [TYPE_I64] = 8,
+  [TYPE_F32] = 4,
+  [TYPE_F64] = 8,
+  [TYPE_V128] = 16,
+  [TYPE_FUNCREF] = 16,
+  [TYPE_EXTERNREF] = 16
+};
+
+struct value_t {
+  enum TYPE type;
+  union {
+    int32_t i32; 
+    int64_t i64; 
+    float f32; 
+    double f64; 
+    __int128 v128; 
+    int64_t funcref; 
+    int64_t extref; 
+  } value;
+};
+
 #define incr(i, len) i++; if (i >= len) {return -1;}
 
-void stack_push(struct stack *s, double a) {
-  s->items[s->count++] = a;
+void stack_push(struct stack *s, const struct value_t *value) {
+  size_t type_size = TYPE_SIZE[value->type];
+  memcpy(&(s->items[s->bytes]), &value->value, type_size);
+  s->items[s->bytes + type_size] = value->type;
+  s->bytes += type_size + 1;
+
   printf("stack: ");
-  for (int i = 0; i < s->count; i++) {
-   printf("%f, ", s->items[i]);
+  for (int i = s->bytes - 1; i > 0; i -= TYPE_SIZE[s->items[i]] + 1) {
+    enum TYPE t = s->items[i];
+    size_t type_size = TYPE_SIZE[t];
+    void *value = &s->items[i - type_size];
+
+    switch (t) {
+      case TYPE_I32:
+        printf("%d (I32)", *(int32_t*)value);
+        break;
+      case TYPE_I64:
+        printf("%ld (I32)", *(int64_t*)value);
+        break;
+      case TYPE_F32:
+        printf("%f (F32)", *(float*)value);
+        break;
+      case TYPE_F64:
+        printf("%f (F64)", *(double*)value);
+        break;
+      case TYPE_V128:
+        printf("%ld (V128)", *(__int128*)value);
+        break;
+      case TYPE_FUNCREF:
+        printf("%ld (EREF)", *(int64_t*)value);
+        break;
+      case TYPE_EXTERNREF:
+        printf("%ld (EREF)", *(int64_t*)value);
+        break;
+    }
+    printf(", ");
   }
   printf("\n");
 } 
 
-double stack_pop(struct stack *s) {
-  s->count--;
-  return s->items[s->count];
-}
-
-double stack_top(struct stack *s) {
-  return s->items[s->count-1];
+void stack_top(struct stack *s, struct value_t *value) {
+  value->type = s->items[s->bytes-1];
+  memcpy(&value->value, &(s->items[s->bytes - 1 - TYPE_SIZE[value->type]]), TYPE_SIZE[value->type]);
 } 
 
+void stack_pop(struct stack *s, struct value_t *value) {
+  stack_top(s, value);
+  s->bytes -= TYPE_SIZE[value->type] + 1;
+}
+
 int parse_type(u_char *binary, int len) {
   int i = 0;
   enum TYPE param = binary[i];
@@ -151,47 +206,71 @@ int parse_instruction(struct module *module, u_char *binary, double param, int l
   int i = 0;
   enum INSTRUCTION instr = (u_char) binary[i];
   u_char *instr_addr = &binary[i];
+  struct value_t a = {0};
+  struct value_t b = {0};
+  struct value_t result = {0};
+
   incr(i, len);
 
   switch (instr) {
-    case INSTR_CALL:
-      int a = binary[i];
+    case INSTR_CALL: {
+      int func_index = binary[i];
       incr(i, len);
-      parse_function(module, module->funcs[a], stack_pop(&module->stack), len);
+      stack_pop(&module->stack, &a);
+      parse_function(module, module->funcs[func_index], a.value.f64, len);
       break;
+      }
     case INSTR_ELSE:
       printf("reached else instruction: impossible!\n");
     case INSTR_END:
       break;
-    case INSTR_F64:
-      break;
     case INSTR_F64_CONST:
-      double k = *(double*)&binary[i];
-      stack_push(&module->stack, k);
+      result.type = TYPE_F64;
+      result.value.f64 = *(double*)&binary[i];
       i += 8;
+      stack_push(&module->stack, &result);
       break;
     case INSTR_F64_LT: {
-      double b = stack_pop(&module->stack);
-      double a = stack_pop(&module->stack);
-      stack_push(&module->stack, a < b);
+      stack_pop(&module->stack, &a);
+      stack_pop(&module->stack, &b);
+      if (a.type != TYPE_F64 || b.type != TYPE_F64) 
+        printf("Wrong types!\n");
+      result.type = TYPE_F64;
+      result.value.f64 = b.value.f64 < a.value.f64;
+      stack_push(&module->stack, &result);
       break;
        }
     case INSTR_F64_MUL: {
-      double b = stack_pop(&module->stack);
-      double a = stack_pop(&module->stack);
-      stack_push(&module->stack, a * b);
+      stack_pop(&module->stack, &a);
+      stack_pop(&module->stack, &b);
+      if (a.type != TYPE_F64 || b.type != TYPE_F64) 
+        printf("Wrong types!\n");
+      result.type = TYPE_F64;
+      result.value.f64 = a.value.f64 * b.value.f64;
+      stack_push(&module->stack, &result);
       break;
       }
     case INSTR_F64_SUB: {
-      double b = stack_pop(&module->stack);
-      double a = stack_pop(&module->stack);
-      stack_push(&module->stack, a - b);
+      stack_pop(&module->stack, &a);
+      stack_pop(&module->stack, &b);
+      if (a.type != TYPE_F64 || b.type != TYPE_F64) 
+        printf("Wrong types!\n");
+      result.type = TYPE_F64;
+      result.value.f64 = b.value.f64 - a.value.f64;
+      stack_push(&module->stack, &result);
       break;
       }
     case INSTR_IF: {
-      double a = stack_pop(&module->stack);
+      stack_pop(&module->stack, &a);
+      enum TYPE condition_type = binary[i];
+      incr(i, len);
+      if (a.type != condition_type) 
+        printf("Wrong types!\n");
+
       while (binary[i] != INSTR_ELSE) {
-        if (a) {
+        // TODO test condition with correct type. 
+        // This might not matter since all types are false with 0x0
+        if (a.value.i64) {
           i += parse_instruction(module, &binary[i], param, len);
         } else {
           incr(i, len);
@@ -199,7 +278,7 @@ int parse_instruction(struct module *module, u_char *binary, double param, int l
       } 
       incr(i, len);
       while (binary[i] != INSTR_END) {
-        if (a) {
+        if (a.value.i64) {
           incr(i, len);
         } else {
           i += parse_instruction(module, &binary[i], param, len);
@@ -208,11 +287,12 @@ int parse_instruction(struct module *module, u_char *binary, double param, int l
       incr(i, len);
       break;
       }
-    case INSTR_LOCAL_GET:
+    case INSTR_LOCAL_GET: {
       int local_index = binary[i];
       incr(i, len);
-      stack_push(&module->stack, param);
+      stack_push(&module->stack, &(struct value_t) {.value.f64 = param, .type = TYPE_F64});
       break;
+      }
     default:
       printf("unknown instruction! %x at %lx\n", instr, instr_addr - module->binary);
       exit(1);
@@ -322,7 +402,7 @@ int parse_section(struct module *module, u_char *binary, int len) {
         module->funcs[function_i] = &binary[i];
         i += parse_function(module, &binary[i], 4, len);
       }
-      printf("result: %f\n", module->stack.items[0]);
+      // printf("result: %f\n", module->stack.items[0]);
       break;
     case Section_Data:
       break;
@@ -339,9 +419,9 @@ int parse_section(struct module *module, u_char *binary, int len) {
 
 int parse_module(u_char *binary, size_t len) {
   int i = 0;
-  u_char *magic = "\0asm";
+  char *magic = "\0asm";
   while (i < 4) {
-    if (binary[i] != magic[i]) {
+    if ((char) binary[i] != magic[i]) {
       fprintf(stderr, "no wasm magic\n");
       return 0;
     }
@@ -377,7 +457,7 @@ int main(int argc, char **argv) {
   stat(argv[1], &st);
   printf("size: %ld\n", st.st_size);
   
-  unsigned char *binary = malloc(st.st_size);
+  u_char *binary = malloc(st.st_size);
   fread(binary, st.st_size, 1, file);
 
   if (parse_module(binary, st.st_size) == -1) {