diff --git a/Makefile b/Makefile
index 45cdc1f..8399348 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,8 @@
 
 CC = gcc
 
+TARGET = matemateak
+
 CFLAGS = -std=c17 -Wall -Wextra -Wpedantic -Wconversion
 LFLAGS = -lm
 
@@ -9,15 +11,17 @@ HEADER_FILES = $(shell find src/ -name *.h)
 
 OBJECT_FILES = $(patsubst %.c, %.o, $(C_FILES))
 
-matemateak: $(OBJECT_FILES)
+all: compile_flags.txt $(TARGET)
+
+$(TARGET): $(OBJECT_FILES)
 	$(CC) -o $@ $(LFLAGS) $^
 
 %.o: %.c $(HEADER_FILES)
 	$(CC) -c -o $@ $(CFLAGS) $<
 
 compile_flags.txt:
-	echo -xc $(C_FLAGS) | sed 's/\s\+/\n/g' > compile_flags.txt
+	echo -xc $(CFLAGS) | sed 's/\s\+/\n/g' > compile_flags.txt
 
 clean:
-	$(RM) $(OBJECT_FILES) matemateak
+	$(RM) $(OBJECT_FILES) $(TARGET)
 
diff --git a/src/lexer.c b/src/lexer.c
index dfb8521..b67db70 100644
--- a/src/lexer.c
+++ b/src/lexer.c
@@ -1,7 +1,19 @@
 #include "lexer.h"
 #include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 
+char* strndup(const char* value, size_t length)
+{
+    size_t string_length = strlen(value);
+    if (string_length >= length)
+        string_length = length;
+    char* allocated = malloc(sizeof(char) * (string_length + 1));
+    strncpy(allocated, value, string_length);
+    return allocated;
+}
+
 bool lexer_done(const Lexer* lexer) { return lexer->index >= lexer->length; }
 
 char lexer_current(const Lexer* lexer) { return lexer->text[lexer->index]; }
@@ -149,10 +161,66 @@ const char* token_type_to_string(TokenType type)
             return "LParen";
         case TokenTypeRParen:
             return "RParen";
+        default:
+            fprintf(
+                stderr,
+                "panic: unexhausted value ./%s:%d %s()\n",
+                __FILE__,
+                __LINE__,
+                __func__
+            );
+            exit(1);
     }
 }
 
 char* token_to_string(Token* token, const char* text)
 {
-    // frick it late
+    char value[32] = { 0 };
+    size_t value_i = 0;
+    for (size_t i = 0; i < token->length && i < 32; i++) {
+        char c = text[token->index + i];
+        switch (c) {
+            case '\\':
+                value[value_i++] = '\\';
+                value[value_i++] = '\\';
+                break;
+            case '\t':
+                value[value_i++] = '\\';
+                value[value_i++] = 't';
+                break;
+            case '\r':
+                value[value_i++] = '\\';
+                value[value_i++] = 'r';
+                break;
+            case '\n':
+                value[value_i++] = '\\';
+                value[value_i++] = 'n';
+                break;
+            case '\0':
+                value[value_i++] = '\\';
+                value[value_i++] = '0';
+                break;
+            case '\"':
+                value[value_i++] = '\\';
+                value[value_i++] = '\"';
+                break;
+            default:
+                value[value_i++] = c;
+                break;
+        }
+    }
+
+    char formattet[128];
+    snprintf(
+        formattet,
+        128,
+        "Token { %11s [%3ld:%-3ld] %3d:%-3d \"%s\" }",
+        token_type_to_string(token->type),
+        token->index,
+        token->length,
+        token->line,
+        token->line,
+        value
+    );
+    return strndup(formattet, 128);
 }
diff --git a/src/lexer.h b/src/lexer.h
index 2718d79..6e86fbb 100644
--- a/src/lexer.h
+++ b/src/lexer.h
@@ -3,6 +3,8 @@
 
 #include <stddef.h>
 
+char* strndup(const char* value, size_t length);
+
 typedef struct {
     size_t index;
     int line, col;
diff --git a/src/main.c b/src/main.c
index 70b4681..d43fd5b 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,4 +1,30 @@
+#include "lexer.h"
+#include "parser.h"
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 
-int main(void) { printf("hello world\n"); }
+int main(void)
+{
+    char* text = "2 * (3 + 4)";
+
+    Lexer lexer1;
+    lexer(&lexer1, text, strlen(text));
+    Token current_token = lexer_next(&lexer1);
+    printf("tokens = [\n");
+    while (current_token.type != TokenTypeEof) {
+        char* token_string = token_to_string(&current_token, text);
+        printf("    %s,\n", token_string);
+        free(token_string);
+        current_token = lexer_next(&lexer1);
+    }
+    printf("]\n");
+
+    Lexer lexer2;
+    lexer(&lexer2, text, strlen(text));
+    Expr* ast = parse(&lexer2, text, strlen(text));
+    char* ast_string = expr_to_string(ast);
+    printf("ast = %s\n", ast_string);
+    free(ast_string);
+    free_expr(ast);
+}
diff --git a/src/parser.c b/src/parser.c
index 95b2e77..aea069d 100644
--- a/src/parser.c
+++ b/src/parser.c
@@ -13,7 +13,7 @@ Expr* error_expr(Position pos, const char* message)
         .type = ExprTypeError,
         .error = (ErrorExpr) {
             .pos = pos,
-            .message = strdup(message),
+            .message = strndup(message, strlen(message)),
         },
     };
     return node;
@@ -89,37 +89,7 @@ Position parser_pos(Parser* parser)
     };
 }
 
-Expr* parser_error(Parser* parser, const char* message)
-{
-    size_t line_width = 0;
-    for (size_t i = 0;
-         i < parser->length && parser->text[parser->current.index + i] != '\r'
-         && parser->text[parser->current.index + i] != '\n';
-         ++i)
-        line_width = i;
-
-    char line[512] = { 0 };
-
-    char underline_indent[512] = { 0 };
-    if (line_width > 0)
-        memset(underline_indent, ' ', line_width - 1);
-
-    char underline[512] = { '^', 0 };
-    memset(underline, '^', parser->current.length);
-
-    char formatted[512 * 4];
-    snprintf(
-        formatted,
-        512 * 4,
-        "error: %s\n     |\n %-4d|%s\n     |%s%s\n",
-        message,
-        parser->current.line,
-        line,
-        underline_indent,
-        underline
-    );
-    return error_expr(parser_pos(parser), formatted);
-}
+Expr* parser_expr(Parser* parser);
 
 Expr* parser_unknown_token_error(Parser* parser)
 {
@@ -127,15 +97,22 @@ Expr* parser_unknown_token_error(Parser* parser)
     snprintf(
         buffer, 128, "unknown char '%c'", parser->text[parser->current.index]
     );
-    return parser_error(parser, buffer);
+    return error_expr(parser_pos(parser), buffer);
 }
 
 Expr* parser_operand(Parser* parser)
 {
     if (parser_current_is(parser, TokenTypeInt)) {
-        return NULL;
+        char buffer[24];
+        strncpy(
+            buffer, &parser->text[parser->current.index], parser->current.length
+        );
+        parser_step(parser);
+        return int_expr(atol(buffer));
     } else if (parser_current_is(parser, TokenTypeEof)) {
-        return parser_error(parser, "unexpected end-of-file");
+        Position pos = parser_pos(parser);
+        parser_step(parser);
+        return error_expr(pos, "unexpected end-of-file");
     } else {
         Expr* error = parser_unknown_token_error(parser);
         parser_step(parser);
@@ -143,13 +120,29 @@ Expr* parser_operand(Parser* parser)
     }
 }
 
+Expr* parser_group(Parser* parser)
+{
+    if (parser_current_is(parser, TokenTypeLParen)) {
+        parser_step(parser);
+        Expr* value = parser_expr(parser);
+        if (!parser_current_is(parser, TokenTypeRParen)) {
+            parser_step(parser);
+            return error_expr(parser_pos(parser), "expected ')'");
+        }
+        parser_step(parser);
+        return value;
+    } else {
+        return parser_operand(parser);
+    }
+}
+
 Expr* parser_unary(Parser* parser)
 {
     if (parser_current_is(parser, TokenTypeMinus)) {
         parser_step(parser);
-        return unary_expr(UnaryExprTypeNegate, parser_operand(parser));
+        return unary_expr(UnaryExprTypeNegate, parser_group(parser));
     } else {
-        return parser_operand(parser);
+        return parser_group(parser);
     }
 }
 
@@ -206,5 +199,130 @@ Expr* parse(Lexer* lexer, const char* text, size_t length)
 
 void free_expr(Expr* expr)
 {
-    //
+    switch (expr->type) {
+        case ExprTypeError:
+            free(expr->error.message);
+            break;
+        case ExprTypeInt:
+            break;
+        case ExprTypeUnary:
+            free_expr(expr->unary.subject);
+            break;
+        case ExprTypeBinary:
+            free_expr(expr->binary.left);
+            free_expr(expr->binary.right);
+            break;
+        default:
+            fprintf(
+                stderr,
+                "panic: unexhausted value ./%s:%d %s()\n",
+                __FILE__,
+                __LINE__,
+                __func__
+            );
+            exit(1);
+    }
+}
+
+const char* unary_expr_type_to_string(UnaryExprType type)
+{
+    switch (type) {
+        case UnaryExprTypeNegate:
+            return "Negate";
+        default:
+            fprintf(
+                stderr,
+                "panic: unexhausted value ./%s:%d %s()\n",
+                __FILE__,
+                __LINE__,
+                __func__
+            );
+            exit(1);
+    }
+}
+
+const char* binary_expr_type_to_string(BinaryExprType type)
+{
+    switch (type) {
+        case BinaryExprTypeAdd:
+            return "Add";
+        case BinaryExprTypeSubtract:
+            return "Subtract";
+        case BinaryExprTypeMultiply:
+            return "Multiply";
+        case BinaryExprTypeDivide:
+            return "Divide";
+        default:
+            fprintf(
+                stderr,
+                "panic: unexhausted value ./%s:%d %s()\n",
+                __FILE__,
+                __LINE__,
+                __func__
+            );
+            exit(1);
+    }
+}
+
+char* expr_to_string(const Expr* expr)
+{
+    printf("expr->type == %d\n", expr->type);
+    switch (expr->type) {
+        case ExprTypeError: {
+            char formattet[65536];
+            snprintf(
+                formattet,
+                65536,
+                "Error { [%ld] %d:%d \"%s\" }",
+                expr->error.pos.index,
+                expr->error.pos.line,
+                expr->error.pos.col,
+                expr->error.message
+            );
+            return strndup(formattet, 65536);
+        }
+        case ExprTypeInt: {
+            char formattet[65536];
+            snprintf(formattet, 65536, "Int(%ld)", expr->int_expr.value);
+            return strndup(formattet, 65536);
+        }
+        case ExprTypeUnary: {
+            char* subject = expr_to_string(expr->unary.subject);
+            char formattet[65536];
+            snprintf(
+                formattet,
+                65536,
+                "Unary { type: %s, subject: %s }",
+                unary_expr_type_to_string(expr->unary.type),
+                subject
+            );
+            free(subject);
+            return strndup(formattet, 65536);
+        }
+        case ExprTypeBinary: {
+            char* left = expr_to_string(expr->binary.left);
+            char* right = expr_to_string(expr->binary.right);
+            char formattet[65536];
+            snprintf(
+                formattet,
+                65536,
+                "Binary { type: %s, left: %s, right: %s }",
+                binary_expr_type_to_string(expr->binary.type),
+                left,
+                right
+            );
+            free(left);
+            free(right);
+            return strndup(formattet, 65536);
+        }
+        default:
+            fprintf(
+                stderr,
+                "panic: unexhausted value ./%s:%d %s()\n",
+                __FILE__,
+                __LINE__,
+                __func__
+            );
+            exit(1);
+    }
 }
diff --git a/src/parser.h b/src/parser.h
index f319990..767a54a 100644
--- a/src/parser.h
+++ b/src/parser.h
@@ -56,5 +56,6 @@ struct Expr {
 
 Expr* parse(Lexer* lexer, const char* text, size_t length);
 void free_expr(Expr* expr);
+char* expr_to_string(const Expr* expr);
 
 #endif