diff --git a/src/ast.c b/src/ast.c
index 9a44e0f..418b4a7 100644
--- a/src/ast.c
+++ b/src/ast.c
@@ -17,6 +17,8 @@ ASTTypeNum* ast_type_num_init(int val) {
 }
 
 void ast_type_num_destroy(ASTTypeNum* num) {
+    if (!num) return
+
     free(num);
 }
 
@@ -31,6 +33,8 @@ ASTTypeCall* ast_type_call_init(char* to, size_t argc, AST** argv) {
 }
 
 void ast_type_call_destroy(ASTTypeCall* call) {
+    if (!call) return
+
     free(call->to);
     for (size_t i = 0; i < call->argc; i++) free(call->argv[i]);
     free(call);
@@ -46,6 +50,8 @@ AST* ast_init(ASTType type, void* data) {
 }
 
 void ast_destroy(AST* ast) {
+    if (!ast) return;
+
     switch (ast->type) {
     case AST_TYPE_NUM:  ast_type_num_destroy(ast->data); break;
     case AST_TYPE_CALL: ast_type_call_destroy(ast->data); break;
diff --git a/src/include/parser.h b/src/include/parser.h
index bee509b..708f3c3 100644
--- a/src/include/parser.h
+++ b/src/include/parser.h
@@ -1,4 +1,19 @@
 #ifndef PARSER_H
 #define PARSER_H
 
+#include "token.h"
+#include "ast.h"
+
+typedef struct {
+    size_t tokenc;      // Number of tokens in tokenv;
+    Token* ctoken;      // The current token.
+    Token** tokenv;     // Token vector.
+    AST* ast;           // Abstract syntax tree.
+} Parser;
+
+Parser* parser_init(size_t tokenc, Token** tokenv);
+void parser_destroy(Parser* parser);
+
+void parser_inc(Parser* parser);
+
 #endif
diff --git a/src/include/stack.h b/src/include/stack.h
new file mode 100644
index 0000000..d0776c0
--- /dev/null
+++ b/src/include/stack.h
@@ -0,0 +1,20 @@
+#ifndef STACK_H
+#define STACK_H
+
+#include <stdlib.h>
+
+#define STACK_MAX 64
+
+typedef struct {
+    size_t i;
+    void* val[STACK_MAX];
+} Stack;
+
+Stack* stack_init();
+// stack->i must be 0.
+void stack_destroy(Stack* stack);
+
+void stack_push(Stack* stack, void* val);
+void* stack_pop(Stack* stack);
+
+#endif
diff --git a/src/parser.c b/src/parser.c
new file mode 100644
index 0000000..fa6b0e1
--- /dev/null
+++ b/src/parser.c
@@ -0,0 +1,24 @@
+#include "include/util.h"
+#include "include/parser.h"
+
+Parser* parser_init(size_t tokenc, Token** tokenv) {
+    talloc(Parser, parser);
+
+    parser->tokenc = tokenc;
+    parser->ctoken = *tokenv;
+    parser->tokenv = tokenv;
+    parser->ast = NULL;
+
+    return parser;
+}
+
+void parser_destroy(Parser* parser) {
+    if (!parser) return;
+
+    // Also frees parser->ctoken.
+    for (int i = 0; i < parser->tokenc; i++) token_destroy(parser->tokenv[i]);
+
+    ast_destroy(parser->ast);
+}
+
+
diff --git a/src/stack.c b/src/stack.c
new file mode 100644
index 0000000..b84f6de
--- /dev/null
+++ b/src/stack.c
@@ -0,0 +1,40 @@
+#include <assert.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "include/util.h"
+#include "include/stack.h"
+
+Stack* stack_init() {
+    talloc(Stack, stack);
+
+    memset(stack->val, 0, sizeof(void*) * STACK_MAX);
+    stack->i = 0;
+
+    return stack;
+}
+
+void stack_destroy(Stack* stack) {
+    // Can only free an empty stack.
+    assert(stack->i == 0);
+    free(stack);
+}
+
+void stack_push(Stack* stack, void* val) {
+    if (stack->i >= STACK_MAX) {
+        log_dbgf("Ran out of stack (max: %d)", STACK_MAX);
+        return;
+    }
+
+    stack->val[stack->i] = val;
+    stack->i++;
+}
+
+void* stack_pop(Stack* stack) {
+    if (stack->i <= 0) {
+        log_dbg("Can't pop empty stack.");
+        return (void*)-1;
+    }
+
+    return stack->val[--stack->i];
+}