diff --git a/.gitignore b/.gitignore
index 5b03d0a..16b9a79 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,6 @@
 *.o
 *.so
+tags
 *.out
 .cache
 compile_commands.json
diff --git a/Makefile b/Makefile
index 598be07..2878383 100644
--- a/Makefile
+++ b/Makefile
@@ -11,7 +11,7 @@ TEST_OBJ_DIR = $(TEST_BUILD_DIR)/obj
 
 CC = clang
 LINK = clang
-CFLAGS = -Wall
+CFLAGS = -Wall -DDBG -ggdb
 LDFLAGS =
 
 SRC_FILES = $(wildcard $(SRC_DIR)/*.c)
@@ -28,6 +28,10 @@ WHITE_BOLD = $(RESETCOLOR)\x1b[37;1m
 
 all: $(TARGET)
 
+release: clean
+release: CFLAGS = -Wall -O2
+release: $(TARGET)
+
 # Link to final binary.
 $(TARGET): $(OBJ_FILES)
 	@ echo -e "$(WHITE_BOLD)Linking $(WHITE)$(TARGET)$(WHITE_BOLD)...$(RESETCOLOR) $(CC) -o $(TARGET) $(OBJ_FILES) $(LDFLAGS)"
@@ -56,5 +60,8 @@ clean:
 	@ echo -e "$(WHITE_BOLD)Cleaning up...$(WHITE) $(OBJ_DIR)/*.o $(TEST_OBJ_DIR)/*.o $(TEST_BUILD_DIR)/test.out $(TARGET)$(RESETCOLOR)"
 	@ rm -rf $(OBJ_DIR)/*.o $(TEST_OBJ_DIR)/*.o $(TEST_BUILD_DIR)/test.out $(TARGET)
 
-.PHONY: all clean test nocolor
+run:
+	./$(TARGET)
+
+.PHONY: all clean test nocolor release
 
diff --git a/examples/test.scl b/examples/test.scl
new file mode 100644
index 0000000..8d2f097
--- /dev/null
+++ b/examples/test.scl
@@ -0,0 +1 @@
+1 + 1
diff --git a/src/dstr.c b/src/dstr.c
new file mode 100644
index 0000000..32c69be
--- /dev/null
+++ b/src/dstr.c
@@ -0,0 +1,27 @@
+#include "include/dstr.h"
+#include <string.h>
+
+Dstr* dstr_init(void) {
+    Dstr* dstr = malloc(sizeof(Dstr));
+
+    dstr->bufsz = DSTR_INITSZ;
+    dstr->buf = malloc(DSTR_INITSZ);
+    dstr->ln = 0;
+
+    return dstr;
+}
+
+void dstr_destroy(Dstr* dstr) {
+    free(dstr->buf);
+    free(dstr);
+}
+
+void dstr_append(Dstr* dest, size_t ln, char* src) {
+    if (dest->ln + ln > dest->bufsz) {
+        // Double the buffer size when overflown.
+        dest->bufsz *= dest->bufsz;
+        dest->buf = realloc(dest->buf, dest->bufsz);
+    }
+
+    strcat(dest->buf + ln, src);
+}
diff --git a/src/include/dstr.h b/src/include/dstr.h
new file mode 100644
index 0000000..cd64c93
--- /dev/null
+++ b/src/include/dstr.h
@@ -0,0 +1,21 @@
+#ifndef DSTR_H
+#define DSTR_H
+
+#include <stdlib.h>
+#include <string.h>
+
+#define DSTR_INITSZ 128
+
+typedef struct {
+    char* buf;    // The buffer containing the string.
+    size_t bufsz; // The size of the buffer.
+    size_t ln;    // The number of characters in the buffer.
+} Dstr;
+
+Dstr* dstr_init(void);
+void dstr_destroy(Dstr* dstr);
+
+// Append ln characters of src to dest.
+void dstr_append(Dstr* dest, size_t ln, char* src);
+
+#endif
diff --git a/src/include/lexer.h b/src/include/lexer.h
index 47827ae..d0032fa 100644
--- a/src/include/lexer.h
+++ b/src/include/lexer.h
@@ -4,7 +4,10 @@
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
+#include <assert.h>
+#include <ctype.h>
 
+#include "util.h"
 #include "token.h"
 
 #define TOKENS_MAX 32
@@ -52,9 +55,4 @@ void lexer_inc(Lexer* lexer);
 // Add a token to the lexer.
 void lexer_add_token(Lexer* lexer, Token* token);
 
-// Print the contents of a lexer.
-void lexer_print(Lexer* lexer);
-
-static char* lexer_state_str(Lexer* lexer);
-
 #endif
diff --git a/src/include/token.h b/src/include/token.h
index 8f1159f..3108b14 100644
--- a/src/include/token.h
+++ b/src/include/token.h
@@ -19,7 +19,10 @@ typedef struct {
 Token* token_init(TokenType type, char* val);
 void token_destroy(Token* token);
 
-void token_print(Token* token);
-static char* token_type_str(Token* token);
+// Returns a string representation of the Token.
+char* token_to_str(Token* token, unsigned int indent);
+
+// Returns a string representation of the TokenType.
+char* token_type_to_str(TokenType t);
 
 #endif
diff --git a/src/include/util.h b/src/include/util.h
index d2f0eee..051b6ce 100644
--- a/src/include/util.h
+++ b/src/include/util.h
@@ -1,6 +1,12 @@
 #ifndef UTIL_H
 #define UTIL_H
 
-int is_even(int n);
+#ifdef DBG
+#define log_dbg(msg) \
+    printf("[dbg:%s:%s:%d] %s\n", __FILE__, __func__, __LINE__, msg); \
+    fflush(stdout);
+#else
+#define log_dbg(msg)
+#endif
 
 #endif
diff --git a/src/lexer.c b/src/lexer.c
index 3dac4f4..d466364 100644
--- a/src/lexer.c
+++ b/src/lexer.c
@@ -1,9 +1,5 @@
 #include "include/lexer.h"
-#include "include/token.h"
-#include <assert.h>
-#include <stdlib.h>
-#include <ctype.h>
-#include <string.h>
+#include "include/util.h"
 
 Lexer* lexer_init(char* src) {
     Lexer* lexer = malloc(sizeof(Lexer));
@@ -12,7 +8,7 @@ Lexer* lexer_init(char* src) {
     lexer->srcl = strlen(src);
     lexer->cchar = lexer->src;
 
-    lexer->tokens = calloc(TOKENS_MAX, sizeof(Token));
+    lexer->tokens = calloc(TOKENS_MAX, sizeof(Token*));
     lexer->ntokens = 0;
     lexer->state = LEXER_STATE_CONFUSED;
 
@@ -22,7 +18,7 @@ Lexer* lexer_init(char* src) {
 void lexer_destroy(Lexer* lexer) {
     free(lexer->src);
 
-    for (int i = 0; i < lexer->ntokens; token_destroy(lexer->tokens[i++]));
+    for (int i = 0; i < lexer->ntokens; i++) token_destroy(lexer->tokens[i]);
 }
 
 void lexer_lex(Lexer* lexer) {
@@ -37,11 +33,13 @@ void lexer_lex(Lexer* lexer) {
 }
 
 void lexer_do_confused(Lexer* lexer) {
+    log_dbg("entered confused mode");
     if (isdigit(*lexer->cchar)) lexer_do_number(lexer);
     else lexer_do_call(lexer);
 }
 
 void lexer_do_number(Lexer* lexer) {
+    log_dbg("entered number mode");
     // Size of the number string.
     size_t numsz;
 
@@ -59,6 +57,7 @@ void lexer_do_number(Lexer* lexer) {
 }
 
 void lexer_do_call(Lexer* lexer) {
+    log_dbg("entered call mode");
     // Size of the call string.
     size_t callsz;
 
@@ -71,6 +70,8 @@ void lexer_do_call(Lexer* lexer) {
     char* call = malloc(callsz + 1);
     memcpy(call, start, callsz);
     call[callsz] = '\0';
+
+    lexer_add_token(lexer, token_init(TOKEN_TYPE_CALL, call));
 }
 
 void lexer_inc(Lexer* lexer) {
@@ -81,29 +82,8 @@ void lexer_add_token(Lexer* lexer, Token* token) {
     assert(lexer->ntokens < TOKENS_MAX);
 
     if (lexer->ntokens < TOKENS_MAX - 1) {
-        lexer->tokens[lexer->ntokens - 1] = token;
+        lexer->tokens[lexer->ntokens] = token;
         lexer->ntokens++;
     }
 }
 
-void lexer_print(Lexer* lexer) {
-    printf("Lexer @%p:\n", lexer);
-    printf("\tsrc: \"%s\"\n", lexer->src);
-    printf("\tsrcl: \"%ld\"\n", lexer->srcl);
-    printf("\tcchar: \"%s\"\n", lexer->cchar);
-    printf("\tntokens: %ld\n", lexer->ntokens);
-    printf("\ttokens: [START]\n");
-    for (int i = 0; i < lexer->ntokens; i++) token_print(lexer->tokens[i]);
-    printf("[END]\n");
-    printf("\tstate: %s\n", lexer_state_str(lexer));
-
-}
-
-static char* lexer_state_str(Lexer* lexer) {
-    switch (lexer->state) {
-    case LEXER_STATE_NUM:      return "NUM";
-    case LEXER_STATE_CALL:     return "CALL";
-    case LEXER_STATE_CONFUSED: return "CONFUSED";
-    default:                   return "???";
-    }
-}
diff --git a/src/main.c b/src/main.c
index 2bf16be..fda8dd7 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,14 +1,17 @@
 #include <stdio.h>
 
+#include "include/token.h"
 #include "include/util.h"
 #include "include/lexer.h"
 
 int main(int argc, char** argv) {
     char* text = malloc(5); 
-    text = "a1b2";
+    text = "aa11";
 
     Lexer* lexer = lexer_init(text);
-    lexer_print(lexer);
     lexer_lex(lexer);
-    lexer_print(lexer);
+
+    printf("%s\n", token_to_str(lexer->tokens[0], 0));
+
+    lexer_destroy(lexer);
 }
diff --git a/src/token.c b/src/token.c
index 368c5ed..07251bb 100644
--- a/src/token.c
+++ b/src/token.c
@@ -1,4 +1,5 @@
 #include "include/token.h"
+#include <stdio.h>
 
 Token* token_init(TokenType type, char* val) {
     Token* t = malloc(sizeof(Token));
@@ -14,17 +15,8 @@ void token_destroy(Token* t) {
     free(t);
 }
 
-void token_print(Token* token) {
-    printf("Token @%p:\n", token);
-    printf("\ttype: %s\n", token_type_str(token));
-    printf("\tval: %s\n", token->val);
-    printf("\tlen: %ld\n", token->len);
-}
-
-static char* token_type_str(Token* token) {
-    switch (token->type) {
-    case TOKEN_TYPE_CALL:   return "CALL";
-    case TOKEN_TYPE_NUMBER: return "NUMBER";
-    default:                return "???";
-    }
+char* token_to_str(Token* token, unsigned int indent) {
+    char* title = malloc(sizeof("Token @ 0x000000000000\n"));
+    sprintf(title, "Token @%p\n", token);
+    return title;
 }
diff --git a/src/util.c b/src/util.c
index 9e9e272..2e34b20 100644
--- a/src/util.c
+++ b/src/util.c
@@ -1,3 +1 @@
 #include "include/util.h"
-
-int is_even(int n) { return !(n % 2); }
diff --git a/test/dstr.c b/test/dstr.c
new file mode 100644
index 0000000..1630415
--- /dev/null
+++ b/test/dstr.c
@@ -0,0 +1,37 @@
+#include "../src/include/dstr.h"
+#include "unity/unity.h"
+#include "registry.h"
+
+void test_dstr_init() {
+    Dstr* dstr = dstr_init();
+
+    TEST_ASSERT_EQUAL_INT(DSTR_INITSZ, dstr->bufsz);
+    TEST_ASSERT_EQUAL_STRING(malloc(DSTR_INITSZ), dstr->buf);
+    TEST_ASSERT_EQUAL_size_t(0, dstr->ln);
+}
+
+void test_dstr_append() {
+    char* str1 = malloc(2);
+    str1 = "h";
+
+    char* str2 = malloc(DSTR_INITSZ);
+    str2 = "h";
+
+
+    Dstr* dstr = dstr_init();
+    dstr_append(dstr, 1, str1);
+
+    TEST_ASSERT_EQUAL_STRING(str2, dstr->buf);
+}
+
+int test_dstr() {
+    UNITY_BEGIN();
+    RUN_TEST(test_dstr_init);
+    RUN_TEST(test_dstr_append);
+    UNITY_END();
+    return 0;
+}
+
+__attribute__((constructor)) void register_dstr() {
+    register_test(test_dstr);
+}
diff --git a/test/lexer.c b/test/lexer.c
new file mode 100644
index 0000000..c3edc58
--- /dev/null
+++ b/test/lexer.c
@@ -0,0 +1,52 @@
+#include "../src/include/lexer.h"
+#include "unity/unity.h"
+#include "registry.h"
+
+void test_lexer_init() {
+    char* src = malloc(sizeof("a1b2"));
+    src = "a1b2";
+    Lexer* lexer = lexer_init(src);
+
+    TEST_ASSERT_EQUAL_STRING(src, lexer->src);
+    TEST_ASSERT_EQUAL_INT(4, lexer->srcl);
+    TEST_ASSERT_EQUAL_CHAR(src[0], *lexer->cchar);
+    TEST_ASSERT_EQUAL_INT(LEXER_STATE_CONFUSED, lexer->state);
+    // Hope that token arr. is right size :).
+    TEST_ASSERT_EQUAL_INT(0, lexer->ntokens);
+}
+
+void test_lexer_lex_callnum() {
+    char* src = malloc(sizeof("a1b2"));
+    src = "a1b2";
+    Lexer* lexer = lexer_init(src);
+
+    Token* tokens[4] = {
+        token_init(TOKEN_TYPE_CALL, "a"),
+        token_init(TOKEN_TYPE_NUMBER, "1"),
+        token_init(TOKEN_TYPE_CALL, "b"),
+        token_init(TOKEN_TYPE_NUMBER, "2"),
+    };
+
+    lexer_lex(lexer);
+
+    TEST_ASSERT_EQUAL_INT(4, lexer->ntokens);
+
+    for (int i = 0; i < 4; i++) {
+        printf("h");
+        fflush(stdout);
+        TEST_ASSERT_EQUAL_INT(tokens[i]->type, lexer->tokens[i]->type);
+        TEST_ASSERT_EQUAL_STRING(tokens[i]->val, lexer->tokens[i]->val);
+    }
+}
+
+int test_lexer() {
+    UNITY_BEGIN();
+    RUN_TEST(test_lexer_init);
+    RUN_TEST(test_lexer_lex_callnum);
+    UNITY_END();
+    return 0;
+}
+
+__attribute__((constructor)) void register_lexer() {
+    register_test(test_lexer);
+}
diff --git a/test/util.c b/test/util.c
deleted file mode 100644
index 0268bee..0000000
--- a/test/util.c
+++ /dev/null
@@ -1,18 +0,0 @@
-#include "../src/include/util.h"
-#include "registry.h"
-#include "unity/unity.h"
-
-void test_is_even() {
-    TEST_ASSERT_EQUAL(0, is_even(1));;
-    TEST_ASSERT_EQUAL(1, is_even(2));
-}
-
-int test_util() {
-    UNITY_BEGIN();
-    RUN_TEST(test_is_even);
-    return UNITY_END();
-}
-
-__attribute__((constructor)) void register_tests_util() {
-    register_test(test_util);
-}