diff --git a/build.sh b/build.sh
index 82751fd..75df40e 100644
--- a/build.sh
+++ b/build.sh
@@ -1,4 +1,4 @@
 #!/bin/bash
 
-gcc -o program main.c -std=c17 -Wall -Wextra -Wpedantic -O3
+gcc -o program -std=c17 -Wall -Wextra -Wpedantic -O3 `cat compile_files.txt`
 
diff --git a/compile_files.txt b/compile_files.txt
new file mode 100644
index 0000000..714ecba
--- /dev/null
+++ b/compile_files.txt
@@ -0,0 +1,7 @@
+main.c
+expr.c
+parser.c
+optimizer.c
+emitter.c
+runtime.c
+
diff --git a/debug.sh b/debug.sh
index 7550f41..8f072b2 100644
--- a/debug.sh
+++ b/debug.sh
@@ -2,7 +2,7 @@
 
 set -xe
 
-gcc -o program main.c -std=c17 -Wall -Wextra -Wpedantic -O3 -g -fsanitize=address,undefined
+gcc -o program -std=c17 -Wall -Wextra -Wpedantic -O3 -g -fsanitize=address,undefined `cat compile_files.txt`
 
 ./program
 
diff --git a/emitter.c b/emitter.c
new file mode 100644
index 0000000..7bcae50
--- /dev/null
+++ b/emitter.c
@@ -0,0 +1,190 @@
+#include "emitter.h"
+#include "expr.h"
+#include "runtime.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+Emitter emitter_create(uint8_t* code_address)
+{
+    return (Emitter) {
+        .code = code_address,
+        .pos = 0,
+        .loop_counter = 0,
+        .cmp_flags_set = false,
+    };
+}
+
+void emitter_push_u8(Emitter* emitter, uint8_t value)
+{
+    emitter->code[emitter->pos] = value;
+    emitter->pos += 1;
+}
+
+void emitter_push_u32(Emitter* emitter, uint32_t value)
+{
+    emitter->code[emitter->pos] = value & 0xFF;
+    emitter->pos += 1;
+    emitter->code[emitter->pos] = (value >> 8) & 0xFF;
+    emitter->pos += 1;
+    emitter->code[emitter->pos] = (value >> 16) & 0xFF;
+    emitter->pos += 1;
+    emitter->code[emitter->pos] = value >> 24;
+    emitter->pos += 1;
+}
+
+void emitter_push_u64(Emitter* emitter, uint64_t value)
+{
+    emitter->code[emitter->pos] = value & 0xFF;
+    emitter->pos += 1;
+    emitter->code[emitter->pos] = (value >> 8) & 0xFF;
+    emitter->pos += 1;
+    emitter->code[emitter->pos] = (value >> 16) & 0xFF;
+    emitter->pos += 1;
+    emitter->code[emitter->pos] = (value >> 24) & 0xFF;
+    emitter->pos += 1;
+    emitter->code[emitter->pos] = (value >> 32) & 0xFF;
+    emitter->pos += 1;
+    emitter->code[emitter->pos] = (value >> 40) & 0xFF;
+    emitter->pos += 1;
+    emitter->code[emitter->pos] = (value >> 48) & 0xFF;
+    emitter->pos += 1;
+    emitter->code[emitter->pos] = (value >> 56) & 0xFF;
+    emitter->pos += 1;
+}
+
+void emitter_emit_expr(Emitter* emitter, Expr* expr)
+{
+    emitter->cmp_flags_set = false;
+    switch (expr->type) {
+        case ExprType_Error:
+            fprintf(stderr, "panic: emitter: program contained errors\n");
+            exit(1);
+            break;
+        case ExprType_Incr:
+            // add BYTE [rbx], 1
+            emitter_push_u8(emitter, 0x80);
+            emitter_push_u8(emitter, 0x03);
+            emitter_push_u8(emitter, expr->value);
+            emitter->cmp_flags_set = true;
+            break;
+        case ExprType_Decr:
+            // sub BYTE [rbx], 1
+            emitter_push_u8(emitter, 0x80);
+            emitter_push_u8(emitter, 0x2b);
+            emitter_push_u8(emitter, expr->value);
+            emitter->cmp_flags_set = true;
+            break;
+        case ExprType_Left:
+            // sub rbx, 1
+            emitter_push_u8(emitter, 0x48);
+            emitter_push_u8(emitter, 0x83);
+            emitter_push_u8(emitter, 0xeb);
+            emitter_push_u8(emitter, expr->value);
+            break;
+        case ExprType_Right:
+            // add rbx, 1
+            emitter_push_u8(emitter, 0x48);
+            emitter_push_u8(emitter, 0x83);
+            emitter_push_u8(emitter, 0xc3);
+            emitter_push_u8(emitter, expr->value);
+            break;
+        case ExprType_Output:
+            // movzx edi, BYTE [rbx]
+            emitter_push_u8(emitter, 0x0f);
+            emitter_push_u8(emitter, 0xb6);
+            emitter_push_u8(emitter, 0x3b);
+            // movabs rax, <put_char>
+            emitter_push_u8(emitter, 0x48);
+            emitter_push_u8(emitter, 0xb8);
+            emitter_push_u64(emitter, (uint64_t)put_char);
+            // call rax
+            emitter_push_u8(emitter, 0xff);
+            emitter_push_u8(emitter, 0xd0);
+            break;
+        case ExprType_Input:
+            // movabs rax, <put_char>
+            emitter_push_u8(emitter, 0x48);
+            emitter_push_u8(emitter, 0xb8);
+            emitter_push_u64(emitter, (uint64_t)get_char);
+            // call rax
+            emitter_push_u8(emitter, 0xff);
+            emitter_push_u8(emitter, 0xd0);
+            // mov BYTE [rbx], al
+            emitter_push_u8(emitter, 0x88);
+            emitter_push_u8(emitter, 0x03);
+            break;
+        case ExprType_Loop:
+            fprintf(stderr, "panic: emitter: unexpected loop\n");
+            exit(1);
+            break;
+        case ExprType_Zero:
+            // mov BYTE [rbx], 0
+            emitter_push_u8(emitter, 0xc6);
+            emitter_push_u8(emitter, 0x03);
+            emitter_push_u8(emitter, 0x00);
+            emitter->cmp_flags_set = true;
+            break;
+    }
+}
+
+void emitter_emit_loop(Emitter* emitter, Expr* expr)
+{
+    int64_t start_loc = (int64_t)&emitter->code[emitter->pos];
+    emitter_emit_expr_vec(emitter, &expr->exprs);
+    if (!emitter->cmp_flags_set) {
+        // cmp BYTE [rbx], 0
+        emitter_push_u8(emitter, 0x80);
+        emitter_push_u8(emitter, 0x3b);
+        emitter_push_u8(emitter, 0x00);
+    }
+
+    int64_t current_loc = (int64_t)&emitter->code[emitter->pos];
+    int32_t relative_address = -(int32_t)(current_loc - start_loc);
+    if (relative_address >= -127) {
+        // jne <current_loc: rel8>
+        emitter_push_u8(emitter, 0x75);
+        emitter_push_u8(emitter, (uint8_t)relative_address - 2);
+    } else {
+        // jne <current_loc: rel32>
+        emitter_push_u8(emitter, 0x0f);
+        emitter_push_u8(emitter, 0x85);
+        emitter_push_u32(emitter, (uint32_t)relative_address - 6);
+    }
+}
+
+void emitter_emit_expr_vec(Emitter* emitter, ExprVec* vec)
+{
+    for (size_t i = 0; i < vec->length; ++i) {
+        Expr* expr = &vec->data[i];
+        if (expr->type == ExprType_Loop) {
+            emitter_emit_loop(emitter, expr);
+        } else {
+            emitter_emit_expr(emitter, expr);
+        }
+    }
+}
+
+void emitter_emit_program(Emitter* emitter, ExprVec* program)
+{
+    // push rbp:
+    emitter_push_u8(emitter, 0x55);
+    // mov rbp, rsp
+    emitter_push_u8(emitter, 0x48);
+    emitter_push_u8(emitter, 0x89);
+    emitter_push_u8(emitter, 0xe5);
+    // push rbx:
+    emitter_push_u8(emitter, 0x53);
+    // mov rbx, rdi
+    emitter_push_u8(emitter, 0x48);
+    emitter_push_u8(emitter, 0x89);
+    emitter_push_u8(emitter, 0xfb);
+
+    emitter_emit_expr_vec(emitter, program);
+
+    // pop rbx
+    emitter_push_u8(emitter, 0x5b);
+    // pop rbx
+    emitter_push_u8(emitter, 0x5d);
+    // ret
+    emitter_push_u8(emitter, 0xc3);
+}
diff --git a/emitter.h b/emitter.h
new file mode 100644
index 0000000..72111dd
--- /dev/null
+++ b/emitter.h
@@ -0,0 +1,25 @@
+#ifndef EMITTER_H
+#define EMITTER_H
+
+#include "expr.h"
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+typedef struct {
+    uint8_t* code;
+    size_t pos;
+    int loop_counter;
+    bool cmp_flags_set;
+} Emitter;
+
+Emitter emitter_create(uint8_t* code_address);
+void emitter_push_u8(Emitter* emitter, uint8_t value);
+void emitter_push_u32(Emitter* emitter, uint32_t value);
+void emitter_push_u64(Emitter* emitter, uint64_t value);
+void emitter_emit_expr(Emitter* emitter, Expr* expr);
+void emitter_emit_loop(Emitter* emitter, Expr* expr);
+void emitter_emit_expr_vec(Emitter* emitter, ExprVec* vec);
+void emitter_emit_program(Emitter* emitter, ExprVec* program);
+
+#endif
diff --git a/expr.c b/expr.c
new file mode 100644
index 0000000..050d2d7
--- /dev/null
+++ b/expr.c
@@ -0,0 +1,192 @@
+#include "expr.h"
+#include "print.h"
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+void expr_vec_construct(ExprVec* vec)
+{
+    *vec = (ExprVec) {
+        .data = malloc(sizeof(Expr) * 8),
+        .capacity = 8,
+        .length = 0,
+    };
+}
+
+void expr_vec_destroy(ExprVec* vec) { free(vec->data); }
+
+void expr_vec_free(ExprVec* vec)
+{
+    for (size_t i = 0; i < vec->length; ++i) {
+        expr_free(&vec->data[i]);
+    }
+    expr_vec_destroy(vec);
+}
+
+void expr_vec_push(ExprVec* vec, Expr expr)
+{
+    if (vec->length + 1 > vec->capacity) {
+        vec->capacity *= 2;
+        vec->data = realloc(vec->data, sizeof(Expr) * vec->capacity);
+    }
+    vec->data[vec->length] = expr;
+    vec->length += 1;
+}
+
+Expr expr_vec_pop(ExprVec* vec)
+{
+    vec->length -= 1;
+    return vec->data[vec->length];
+}
+
+bool expr_vec_equal(const ExprVec* self, const ExprVec* other)
+{
+    if (self->length != other->length) {
+        return false;
+    }
+    for (size_t i = 0; i < self->length; ++i) {
+        if (!expr_equal(&self->data[i], &other->data[i])) {
+            return false;
+        }
+    }
+    return true;
+}
+
+void expr_free(Expr* expr)
+{
+    switch (expr->type) {
+        case ExprType_Loop:
+            expr_vec_free(&expr->exprs);
+            break;
+        default:
+            break;
+    }
+}
+
+const char* expr_bracket_color(int depth)
+{
+    switch (depth % 3) {
+        case 0:
+            return color_bright_yellow;
+        case 1:
+            return color_magenta;
+        case 2:
+            return color_cyan;
+    }
+    return NULL;
+}
+
+void expr_stringify_concat_value(Expr* expr, char* acc, int depth)
+{
+    strcat(acc, color_bold);
+    strcat(acc, expr_bracket_color(depth));
+    strcat(acc, "(");
+    strcat(acc, color_reset);
+    char value[16] = { 0 };
+    snprintf(value, 16, "%d", expr->value);
+    strcat(acc, value);
+    strcat(acc, color_bold);
+    strcat(acc, expr_bracket_color(depth));
+    strcat(acc, ")");
+    strcat(acc, color_reset);
+}
+
+void expr_vec_stringify(ExprVec* vec, char* acc, int depth)
+{
+    strcat(acc, color_bold);
+    strcat(acc, expr_bracket_color(depth));
+    strcat(acc, "[");
+    strcat(acc, color_reset);
+    for (size_t i = 0; i < vec->length; ++i) {
+        if (i != 0) {
+            strcat(acc, " ");
+        }
+        expr_stringify(&vec->data[i], acc, depth + 1);
+    }
+    strcat(acc, color_bold);
+    strcat(acc, expr_bracket_color(depth));
+    strcat(acc, "]");
+    strcat(acc, color_reset);
+}
+
+void expr_stringify(Expr* expr, char* acc, int depth)
+{
+    switch (expr->type) {
+        case ExprType_Error:
+            strcat(acc, color_bright_red);
+            strcat(acc, "Error");
+            strcat(acc, color_reset);
+            break;
+        case ExprType_Incr:
+            strcat(acc, color_yellow);
+            strcat(acc, "Incr");
+            strcat(acc, color_reset);
+            expr_stringify_concat_value(expr, acc, depth);
+            break;
+        case ExprType_Decr:
+            strcat(acc, color_yellow);
+            strcat(acc, "Decr");
+            strcat(acc, color_reset);
+            expr_stringify_concat_value(expr, acc, depth);
+            break;
+        case ExprType_Left:
+            strcat(acc, color_green);
+            strcat(acc, "Left");
+            strcat(acc, color_reset);
+            expr_stringify_concat_value(expr, acc, depth);
+            break;
+        case ExprType_Right:
+            strcat(acc, color_green);
+            strcat(acc, "Right");
+            strcat(acc, color_reset);
+            expr_stringify_concat_value(expr, acc, depth);
+            break;
+        case ExprType_Output:
+            strcat(acc, color_bright_gray);
+            strcat(acc, "Output");
+            strcat(acc, color_reset);
+            break;
+        case ExprType_Input:
+            strcat(acc, color_bright_gray);
+            strcat(acc, "Input");
+            strcat(acc, color_reset);
+            break;
+        case ExprType_Loop:
+            strcat(acc, color_bright_red);
+            strcat(acc, "Loop");
+            expr_vec_stringify(&expr->exprs, acc, depth);
+            strcat(acc, color_reset);
+            break;
+        case ExprType_Zero:
+            strcat(acc, color_yellow);
+            strcat(acc, "Zero");
+            strcat(acc, color_reset);
+            break;
+    }
+}
+
+bool expr_equal(const Expr* self, const Expr* other)
+{
+    if (self->type != other->type) {
+        return false;
+    }
+    switch (self->type) {
+        case ExprType_Incr:
+        case ExprType_Decr:
+        case ExprType_Left:
+        case ExprType_Right:
+            if (self->value != other->value) {
+                return false;
+            }
+            break;
+        case ExprType_Loop:
+            if (!expr_vec_equal(&self->exprs, &other->exprs)) {
+                return false;
+            }
+            break;
+        default:
+            break;
+    }
+    return true;
+}
diff --git a/expr.h b/expr.h
new file mode 100644
index 0000000..8b6c2ad
--- /dev/null
+++ b/expr.h
@@ -0,0 +1,49 @@
+#ifndef EXPR_H
+#define EXPR_H
+
+#include <stdbool.h>
+#include <stddef.h>
+
+typedef enum {
+    ExprType_Error,
+    ExprType_Incr,
+    ExprType_Decr,
+    ExprType_Left,
+    ExprType_Right,
+    ExprType_Output,
+    ExprType_Input,
+    ExprType_Loop,
+    ExprType_Zero,
+} ExprType;
+
+typedef struct Expr Expr;
+
+typedef struct ExprVec {
+    Expr* data;
+    size_t capacity;
+    size_t length;
+} ExprVec;
+
+void expr_vec_construct(ExprVec* vec);
+void expr_vec_destroy(ExprVec* vec);
+void expr_vec_free(ExprVec* vec);
+void expr_vec_push(ExprVec* vec, Expr expr);
+Expr expr_vec_pop(ExprVec* vec);
+bool expr_vec_equal(const ExprVec* self, const ExprVec* other);
+
+struct Expr {
+    ExprType type;
+    union {
+        int value;
+        ExprVec exprs;
+    };
+};
+
+void expr_free(Expr* expr);
+const char* expr_bracket_color(int depth);
+void expr_stringify_concat_value(Expr* expr, char* acc, int depth);
+void expr_vec_stringify(ExprVec* vec, char* acc, int depth);
+void expr_stringify(Expr* expr, char* acc, int depth);
+bool expr_equal(const Expr* self, const Expr* other);
+
+#endif
diff --git a/main.c b/main.c
index 51eb875..aac86a8 100644
--- a/main.c
+++ b/main.c
@@ -1,3 +1,8 @@
+#include "emitter.h"
+#include "expr.h"
+#include "optimizer.h"
+#include "parser.h"
+#include "print.h"
 #include <stdbool.h>
 #include <stdint.h>
 #include <stdio.h>
@@ -5,766 +10,17 @@
 #include <string.h>
 #include <sys/mman.h>
 
-typedef enum {
-    Token_Eof,
-    Token_Plus,
-    Token_Minus,
-    Token_LT,
-    Token_GT,
-    Token_Dot,
-    Token_Comma,
-    Token_LBracket,
-    Token_RBracket
-} Token;
-
-typedef struct {
-    const char* text;
-    size_t index;
-    size_t length;
-} Lexer;
-
-Lexer lexer_create(const char* text, size_t length)
+int main(int argc, char** argv)
 {
-    return (Lexer) { .text = text, .index = 0, .length = length };
-}
-
-void lexer_step(Lexer* lexer) { lexer->index += 1; }
-
-Token lexer_next(Lexer* lexer)
-{
-    if (lexer->index >= lexer->length) {
-        return Token_Eof;
-    }
-    switch (lexer->text[lexer->index]) {
-        case '+':
-            return (lexer_step(lexer), Token_Plus);
-        case '-':
-            return (lexer_step(lexer), Token_Minus);
-        case '<':
-            return (lexer_step(lexer), Token_LT);
-        case '>':
-            return (lexer_step(lexer), Token_GT);
-        case '.':
-            return (lexer_step(lexer), Token_Dot);
-        case ',':
-            return (lexer_step(lexer), Token_Comma);
-        case '[':
-            return (lexer_step(lexer), Token_LBracket);
-        case ']':
-            return (lexer_step(lexer), Token_RBracket);
-        default:
-            return (lexer_step(lexer), lexer_next(lexer));
-    }
-}
-
-typedef enum {
-    ExprType_Error,
-    ExprType_Incr,
-    ExprType_Decr,
-    ExprType_Left,
-    ExprType_Right,
-    ExprType_Output,
-    ExprType_Input,
-    ExprType_Loop,
-    ExprType_Zero,
-} ExprType;
-
-typedef struct Expr Expr;
-
-typedef struct ExprVec {
-    Expr* data;
-    size_t capacity;
-    size_t length;
-} ExprVec;
-
-struct Expr {
-    ExprType type;
-    union {
-        int value;
-        ExprVec exprs;
-    };
-};
-
-void expr_vec_construct(ExprVec* vec)
-{
-    *vec = (ExprVec) {
-        .data = malloc(sizeof(Expr) * 8),
-        .capacity = 8,
-        .length = 0,
-    };
-}
-void expr_vec_destroy(ExprVec* vec) { free(vec->data); }
-
-void expr_free(Expr* expr);
-void expr_vec_free(ExprVec* vec)
-{
-    for (size_t i = 0; i < vec->length; ++i) {
-        expr_free(&vec->data[i]);
-    }
-    expr_vec_destroy(vec);
-}
-
-void expr_vec_push(ExprVec* vec, Expr expr)
-{
-    if (vec->length + 1 > vec->capacity) {
-        vec->capacity *= 2;
-        vec->data = realloc(vec->data, sizeof(Expr) * vec->capacity);
-    }
-    vec->data[vec->length] = expr;
-    vec->length += 1;
-}
-Expr expr_vec_pop(ExprVec* vec)
-{
-    vec->length -= 1;
-    return vec->data[vec->length];
-}
-
-void expr_free(Expr* expr)
-{
-    switch (expr->type) {
-        case ExprType_Loop:
-            expr_vec_free(&expr->exprs);
-            break;
-        default:
-            break;
-    }
-}
-
-const char* color_reset = "\x1b[0m";
-const char* color_bold = "\x1b[1m";
-
-const char* color_black = "\x1b[30m";
-const char* color_red = "\x1b[31m";
-const char* color_green = "\x1b[32m";
-const char* color_yellow = "\x1b[33m";
-const char* color_blue = "\x1b[34m";
-const char* color_magenta = "\x1b[35m";
-const char* color_cyan = "\x1b[36m";
-const char* color_bright_gray = "\x1b[37m";
-
-const char* color_gray = "\x1b[90m";
-const char* color_bright_red = "\x1b[91m";
-const char* color_bright_green = "\x1b[92m";
-const char* color_bright_yellow = "\x1b[93m";
-const char* color_bright_blue = "\x1b[94m";
-const char* color_bright_magenta = "\x1b[95m";
-const char* color_bright_cyan = "\x1b[96m";
-const char* color_white = "\x1b[97m";
-
-const char* expr_bracket_color(int depth)
-{
-    switch (depth % 3) {
-        case 0:
-            return color_bright_yellow;
-        case 1:
-            return color_magenta;
-        case 2:
-            return color_cyan;
-    }
-    return NULL;
-}
-
-void expr_stringify_concat_value(Expr* expr, char* acc, int depth)
-{
-    strcat(acc, color_bold);
-    strcat(acc, expr_bracket_color(depth));
-    strcat(acc, "(");
-    strcat(acc, color_reset);
-    char value[16] = { 0 };
-    snprintf(value, 16, "%d", expr->value);
-    strcat(acc, value);
-    strcat(acc, color_bold);
-    strcat(acc, expr_bracket_color(depth));
-    strcat(acc, ")");
-    strcat(acc, color_reset);
-}
-
-void expr_stringify(Expr* expr, char* acc, int depth);
-
-void expr_vec_stringify(ExprVec* vec, char* acc, int depth)
-{
-    strcat(acc, color_bold);
-    strcat(acc, expr_bracket_color(depth));
-    strcat(acc, "[");
-    strcat(acc, color_reset);
-    for (size_t i = 0; i < vec->length; ++i) {
-        if (i != 0) {
-            strcat(acc, " ");
-        }
-        expr_stringify(&vec->data[i], acc, depth + 1);
-    }
-    strcat(acc, color_bold);
-    strcat(acc, expr_bracket_color(depth));
-    strcat(acc, "]");
-    strcat(acc, color_reset);
-}
-
-void expr_stringify(Expr* expr, char* acc, int depth)
-{
-    switch (expr->type) {
-        case ExprType_Error:
-            strcat(acc, color_bright_red);
-            strcat(acc, "Error");
-            strcat(acc, color_reset);
-            break;
-        case ExprType_Incr:
-            strcat(acc, color_yellow);
-            strcat(acc, "Incr");
-            strcat(acc, color_reset);
-            expr_stringify_concat_value(expr, acc, depth);
-            break;
-        case ExprType_Decr:
-            strcat(acc, color_yellow);
-            strcat(acc, "Decr");
-            strcat(acc, color_reset);
-            expr_stringify_concat_value(expr, acc, depth);
-            break;
-        case ExprType_Left:
-            strcat(acc, color_green);
-            strcat(acc, "Left");
-            strcat(acc, color_reset);
-            expr_stringify_concat_value(expr, acc, depth);
-            break;
-        case ExprType_Right:
-            strcat(acc, color_green);
-            strcat(acc, "Right");
-            strcat(acc, color_reset);
-            expr_stringify_concat_value(expr, acc, depth);
-            break;
-        case ExprType_Output:
-            strcat(acc, color_bright_gray);
-            strcat(acc, "Output");
-            strcat(acc, color_reset);
-            break;
-        case ExprType_Input:
-            strcat(acc, color_bright_gray);
-            strcat(acc, "Input");
-            strcat(acc, color_reset);
-            break;
-        case ExprType_Loop:
-            strcat(acc, color_bright_red);
-            strcat(acc, "Loop");
-            expr_vec_stringify(&expr->exprs, acc, depth);
-            strcat(acc, color_reset);
-            break;
-        case ExprType_Zero:
-            strcat(acc, color_yellow);
-            strcat(acc, "Zero");
-            strcat(acc, color_reset);
-            break;
-    }
-}
-
-bool expr_equal(const Expr* self, const Expr* other);
-
-bool expr_vec_equal(const ExprVec* self, const ExprVec* other)
-{
-    if (self->length != other->length) {
-        return false;
-    }
-    for (size_t i = 0; i < self->length; ++i) {
-        if (!expr_equal(&self->data[i], &other->data[i])) {
-            return false;
-        }
-    }
-    return true;
-}
-
-bool expr_equal(const Expr* self, const Expr* other)
-{
-    if (self->type != other->type) {
-        return false;
-    }
-    switch (self->type) {
-        case ExprType_Incr:
-        case ExprType_Decr:
-        case ExprType_Left:
-        case ExprType_Right:
-            if (self->value != other->value) {
-                return false;
-            }
-            break;
-        case ExprType_Loop:
-            if (!expr_vec_equal(&self->exprs, &other->exprs)) {
-                return false;
-            }
-            break;
-        default:
-            break;
-    }
-    return true;
-}
-
-typedef struct {
-    Lexer lexer;
-    Token current;
-} Parser;
-
-Parser parser_create(const char* text, size_t length)
-{
-    Lexer lexer = lexer_create(text, length);
-    return (Parser) {
-        .lexer = lexer,
-        .current = lexer_next(&lexer),
-    };
-}
-
-void parser_step(Parser* parser)
-{
-    parser->current = lexer_next(&parser->lexer);
-}
-
-Expr parser_parse_expr(Parser* parser);
-
-Expr parser_parse_loop(Parser* parser)
-{
-    parser_step(parser);
-    ExprVec exprs;
-    expr_vec_construct(&exprs);
-    while (parser->current != Token_Eof && parser->current != Token_RBracket) {
-        expr_vec_push(&exprs, parser_parse_expr(parser));
-    }
-    if (parser->current != Token_RBracket) {
-        return (Expr) { .type = ExprType_Error };
-    }
-    parser_step(parser);
-    return (Expr) { .type = ExprType_Loop, .exprs = exprs };
-}
-
-Expr parser_parse_expr(Parser* parser)
-{
-    switch (parser->current) {
-        case Token_Plus:
-            return (
-                parser_step(parser),
-                (Expr) { .type = ExprType_Incr, .value = 1 }
-            );
-        case Token_Minus:
-            return (
-                parser_step(parser),
-                (Expr) { .type = ExprType_Decr, .value = 1 }
-            );
-        case Token_LT:
-            return (
-                parser_step(parser),
-                (Expr) { .type = ExprType_Left, .value = 1 }
-            );
-        case Token_GT:
-            return (
-                parser_step(parser),
-                (Expr) { .type = ExprType_Right, .value = 1 }
-            );
-        case Token_Dot:
-            return (parser_step(parser), (Expr) { .type = ExprType_Output });
-        case Token_Comma:
-            return (parser_step(parser), (Expr) { .type = ExprType_Input });
-        case Token_LBracket:
-            return parser_parse_loop(parser);
-        default:
-            return (parser_step(parser), (Expr) { .type = ExprType_Error });
-    }
-}
-
-ExprVec parser_parse(Parser* parser)
-{
-    ExprVec exprs;
-    expr_vec_construct(&exprs);
-    while (parser->current != Token_Eof) {
-        expr_vec_push(&exprs, parser_parse_expr(parser));
-    }
-    return exprs;
-}
-
-Expr expr_optimize_fold_adjecent(const Expr* expr);
-ExprVec expr_vec_optimize_fold_adjecent(const ExprVec* vec)
-{
-    ExprVec exprs;
-    expr_vec_construct(&exprs);
-    if (vec->length == 0) {
-        return exprs;
-    }
-    Expr a = expr_optimize_fold_adjecent(&vec->data[0]);
-    for (size_t i = 1; i < vec->length; ++i) {
-        Expr b = expr_optimize_fold_adjecent(&vec->data[i]);
-        switch (a.type) {
-            case ExprType_Incr:
-            case ExprType_Decr:
-            case ExprType_Left:
-            case ExprType_Right:
-                if (a.type != b.type) {
-                    expr_vec_push(&exprs, a);
-                    a = b;
-                } else {
-                    a.value += b.value;
-                }
-                break;
-            default:
-                expr_vec_push(&exprs, a);
-                a = b;
-        }
-    }
-    expr_vec_push(&exprs, a);
-    return exprs;
-}
-Expr expr_optimize_fold_adjecent(const Expr* expr)
-{
-    if (expr->type == ExprType_Loop) {
-        return (Expr) {
-            .type = ExprType_Loop,
-            .exprs = expr_vec_optimize_fold_adjecent(&expr->exprs),
-        };
-    } else {
-        return *expr;
-    }
-}
-
-Expr expr_optimize_eliminate_negation(const Expr* expr);
-ExprVec expr_vec_optimize_eliminate_negation(const ExprVec* vec)
-{
-    ExprVec exprs;
-    expr_vec_construct(&exprs);
-    if (vec->length == 0) {
-        return exprs;
-    }
-    expr_vec_push(&exprs, expr_optimize_eliminate_negation(&vec->data[0]));
-    for (size_t i = 1; i < vec->length; ++i) {
-        expr_vec_push(&exprs, expr_optimize_eliminate_negation(&vec->data[i]));
-        Expr* a = &exprs.data[i - 1];
-        Expr* b = &exprs.data[i];
-        if (a->type == ExprType_Incr && b->type == ExprType_Decr) {
-            if (a->value > b->value) {
-                a->value -= b->value;
-                expr_vec_pop(&exprs);
-            } else if (a->value < b->value) {
-                *a = (Expr) { .type = ExprType_Decr,
-                              .value = b->value - a->value };
-                expr_vec_pop(&exprs);
-            } else {
-                expr_vec_pop(&exprs);
-                expr_vec_pop(&exprs);
-            }
-        } else if (a->type == ExprType_Decr && b->type == ExprType_Incr) {
-            if (a->value > b->value) {
-                a->value -= b->value;
-                expr_vec_pop(&exprs);
-            } else if (a->value < b->value) {
-                *a = (Expr) { .type = ExprType_Incr,
-                              .value = b->value - a->value };
-                expr_vec_pop(&exprs);
-            } else {
-                expr_vec_pop(&exprs);
-                expr_vec_pop(&exprs);
-            }
-        }
-        if (a->type == ExprType_Left && b->type == ExprType_Right) {
-            if (a->value > b->value) {
-                a->value -= b->value;
-                expr_vec_pop(&exprs);
-            } else if (a->value < b->value) {
-                *a = (Expr) { .type = ExprType_Right,
-                              .value = b->value - a->value };
-                expr_vec_pop(&exprs);
-            } else {
-                expr_vec_pop(&exprs);
-                expr_vec_pop(&exprs);
-            }
-        } else if (a->type == ExprType_Right && b->type == ExprType_Left) {
-            if (a->value > b->value) {
-                a->value -= b->value;
-                expr_vec_pop(&exprs);
-            } else if (a->value < b->value) {
-                *a = (Expr) { .type = ExprType_Left,
-                              .value = b->value - a->value };
-                expr_vec_pop(&exprs);
-            } else {
-                expr_vec_pop(&exprs);
-                expr_vec_pop(&exprs);
-            }
-        }
-    }
-    return exprs;
-}
-Expr expr_optimize_eliminate_negation(const Expr* expr)
-{
-    if (expr->type == ExprType_Loop) {
-        return (Expr) {
-            .type = ExprType_Loop,
-            .exprs = expr_vec_optimize_eliminate_negation(&expr->exprs),
-        };
-    } else {
-        return *expr;
-    }
-}
-
-Expr expr_optimize_eliminate_overflow(const Expr* expr);
-ExprVec expr_vec_optimize_eliminate_overflow(const ExprVec* vec)
-{
-    ExprVec exprs;
-    expr_vec_construct(&exprs);
-    for (size_t i = 0; i < vec->length; ++i) {
-        expr_vec_push(&exprs, expr_optimize_eliminate_overflow(&vec->data[i]));
-    }
-    return exprs;
-}
-Expr expr_optimize_eliminate_overflow(const Expr* expr)
-{
-    if (expr->type == ExprType_Loop) {
-        return (Expr) {
-            .type = ExprType_Loop,
-            .exprs = expr_vec_optimize_eliminate_overflow(&expr->exprs),
-        };
-    } else if (expr->value > 255) {
-        return (Expr) { .type = expr->type, .value = expr->value % 256 };
-    } else {
-        return *expr;
-    }
-}
-
-Expr expr_optimize_replace_zeroing_loops(const Expr* expr);
-ExprVec expr_vec_optimize_replace_zeroing_loops(const ExprVec* vec)
-{
-    ExprVec exprs;
-    expr_vec_construct(&exprs);
-    for (size_t i = 0; i < vec->length; ++i) {
-        expr_vec_push(
-            &exprs, expr_optimize_replace_zeroing_loops(&vec->data[i])
-        );
-    }
-    return exprs;
-}
-Expr expr_optimize_replace_zeroing_loops(const Expr* expr)
-{
-    if (expr->type == ExprType_Loop) {
-        if (expr->exprs.length == 1
-            && (expr->exprs.data[0].type == ExprType_Incr
-                || expr->exprs.data[0].type == ExprType_Decr)
-            && expr->exprs.data[0].value % 2 != 0) {
-            return (Expr) { .type = ExprType_Zero };
-        } else {
-            return (Expr) {
-                .type = ExprType_Loop,
-                .exprs = expr_vec_optimize_replace_zeroing_loops(&expr->exprs),
-            };
-        }
-    } else {
-        return *expr;
-    }
-}
-
-typedef struct {
-    uint8_t* code;
-    size_t pos;
-    int loop_counter;
-    bool cmp_flags_set;
-} Emitter;
-
-Emitter emitter_create(uint8_t* code_address)
-{
-    return (Emitter) {
-        .code = code_address,
-        .pos = 0,
-        .loop_counter = 0,
-        .cmp_flags_set = false,
-    };
-}
-
-void emitter_push_u8(Emitter* emitter, uint8_t value)
-{
-    emitter->code[emitter->pos] = value;
-    emitter->pos += 1;
-}
-
-void emitter_push_u32(Emitter* emitter, uint32_t value)
-{
-    emitter->code[emitter->pos] = value & 0xFF;
-    emitter->pos += 1;
-    emitter->code[emitter->pos] = (value >> 8) & 0xFF;
-    emitter->pos += 1;
-    emitter->code[emitter->pos] = (value >> 16) & 0xFF;
-    emitter->pos += 1;
-    emitter->code[emitter->pos] = value >> 24;
-    emitter->pos += 1;
-}
-
-void emitter_push_u64(Emitter* emitter, uint64_t value)
-{
-    emitter->code[emitter->pos] = value & 0xFF;
-    emitter->pos += 1;
-    emitter->code[emitter->pos] = (value >> 8) & 0xFF;
-    emitter->pos += 1;
-    emitter->code[emitter->pos] = (value >> 16) & 0xFF;
-    emitter->pos += 1;
-    emitter->code[emitter->pos] = (value >> 24) & 0xFF;
-    emitter->pos += 1;
-    emitter->code[emitter->pos] = (value >> 32) & 0xFF;
-    emitter->pos += 1;
-    emitter->code[emitter->pos] = (value >> 40) & 0xFF;
-    emitter->pos += 1;
-    emitter->code[emitter->pos] = (value >> 48) & 0xFF;
-    emitter->pos += 1;
-    emitter->code[emitter->pos] = (value >> 56) & 0xFF;
-    emitter->pos += 1;
-}
-
-uint8_t get_char(void) { return (uint8_t)fgetc(stdin); }
-void put_char(uint8_t v) { fputc(v, stdout); }
-
-void emitter_emit_expr(Emitter* emitter, Expr* expr)
-{
-    emitter->cmp_flags_set = false;
-    switch (expr->type) {
-        case ExprType_Error:
-            fprintf(stderr, "panic: emitter: program contained errors\n");
-            exit(1);
-            break;
-        case ExprType_Incr:
-            // add BYTE [rbx], 1
-            emitter_push_u8(emitter, 0x80);
-            emitter_push_u8(emitter, 0x03);
-            emitter_push_u8(emitter, expr->value);
-            emitter->cmp_flags_set = true;
-            break;
-        case ExprType_Decr:
-            // sub BYTE [rbx], 1
-            emitter_push_u8(emitter, 0x80);
-            emitter_push_u8(emitter, 0x2b);
-            emitter_push_u8(emitter, expr->value);
-            emitter->cmp_flags_set = true;
-            break;
-        case ExprType_Left:
-            // sub rbx, 1
-            emitter_push_u8(emitter, 0x48);
-            emitter_push_u8(emitter, 0x83);
-            emitter_push_u8(emitter, 0xeb);
-            emitter_push_u8(emitter, expr->value);
-            break;
-        case ExprType_Right:
-            // add rbx, 1
-            emitter_push_u8(emitter, 0x48);
-            emitter_push_u8(emitter, 0x83);
-            emitter_push_u8(emitter, 0xc3);
-            emitter_push_u8(emitter, expr->value);
-            break;
-        case ExprType_Output:
-            // movzx edi, BYTE [rbx]
-            emitter_push_u8(emitter, 0x0f);
-            emitter_push_u8(emitter, 0xb6);
-            emitter_push_u8(emitter, 0x3b);
-            // movabs rax, <put_char>
-            emitter_push_u8(emitter, 0x48);
-            emitter_push_u8(emitter, 0xb8);
-            emitter_push_u64(emitter, (uint64_t)put_char);
-            // call rax
-            emitter_push_u8(emitter, 0xff);
-            emitter_push_u8(emitter, 0xd0);
-            break;
-        case ExprType_Input:
-            // movabs rax, <put_char>
-            emitter_push_u8(emitter, 0x48);
-            emitter_push_u8(emitter, 0xb8);
-            emitter_push_u64(emitter, (uint64_t)get_char);
-            // call rax
-            emitter_push_u8(emitter, 0xff);
-            emitter_push_u8(emitter, 0xd0);
-            // mov BYTE [rbx], al
-            emitter_push_u8(emitter, 0x88);
-            emitter_push_u8(emitter, 0x03);
-            break;
-        case ExprType_Loop:
-            fprintf(stderr, "panic: emitter: unexpected loop\n");
-            exit(1);
-            break;
-        case ExprType_Zero:
-            // mov BYTE [rbx], 0
-            emitter_push_u8(emitter, 0xc6);
-            emitter_push_u8(emitter, 0x03);
-            emitter_push_u8(emitter, 0x00);
-            emitter->cmp_flags_set = true;
-            break;
-    }
-}
-
-void emitter_emit_expr_vec(Emitter* emitter, ExprVec* vec);
-
-void emitter_emit_loop(Emitter* emitter, Expr* expr)
-{
-    int64_t start_loc = (int64_t)&emitter->code[emitter->pos];
-    emitter_emit_expr_vec(emitter, &expr->exprs);
-    if (!emitter->cmp_flags_set) {
-        // cmp BYTE [rbx], 0
-        emitter_push_u8(emitter, 0x80);
-        emitter_push_u8(emitter, 0x3b);
-        emitter_push_u8(emitter, 0x00);
-    }
-
-    int64_t current_loc = (int64_t)&emitter->code[emitter->pos];
-    int32_t relative_address = -(int32_t)(current_loc - start_loc);
-    if (relative_address >= -127) {
-        // jne <current_loc: rel8>
-        emitter_push_u8(emitter, 0x75);
-        emitter_push_u8(emitter, (uint8_t)relative_address - 2);
-    } else {
-        // jne <current_loc: rel32>
-        emitter_push_u8(emitter, 0x0f);
-        emitter_push_u8(emitter, 0x85);
-        emitter_push_u32(emitter, (uint32_t)relative_address - 6);
-    }
-}
-
-void emitter_emit_expr_vec(Emitter* emitter, ExprVec* vec)
-{
-    for (size_t i = 0; i < vec->length; ++i) {
-        Expr* expr = &vec->data[i];
-        if (expr->type == ExprType_Loop) {
-            emitter_emit_loop(emitter, expr);
-        } else {
-            emitter_emit_expr(emitter, expr);
-        }
-    }
-}
-
-void emitter_emit_program(Emitter* emitter, ExprVec* program)
-{
-    // push rbp:
-    emitter_push_u8(emitter, 0x55);
-    // mov rbp, rsp
-    emitter_push_u8(emitter, 0x48);
-    emitter_push_u8(emitter, 0x89);
-    emitter_push_u8(emitter, 0xe5);
-    // push rbx:
-    emitter_push_u8(emitter, 0x53);
-    // mov rbx, rdi
-    emitter_push_u8(emitter, 0x48);
-    emitter_push_u8(emitter, 0x89);
-    emitter_push_u8(emitter, 0xfb);
-
-    emitter_emit_expr_vec(emitter, program);
-
-    // pop rbx
-    emitter_push_u8(emitter, 0x5b);
-    // pop rbx
-    emitter_push_u8(emitter, 0x5d);
-    // ret
-    emitter_push_u8(emitter, 0xc3);
-}
-
-int main(void)
-{
-    // const char* text
-    //     = "+++[>[-]++++++++++++++++++++++++++++++++++++++++++++++++++"
-    //       "++++++++++++++++++"
-    //       "++++.---.++++++++++++++++++++.[-]++++++++++.<-]";
-    const char* text = ">++[<+++++++++++++>-]<[[>+>+<<-]>[<+>-]++++++++"
-                       "[>++++++++<-]>.[-]<<>++++++++++[>++++++++++[>++"
-                       "++++++++[>++++++++++[>++++++++++[>++++++++++[>+"
-                       "+++++++++[-]<-]<-]<-]<-]<-]<-]<-]++++++++++.";
-
+    const char* text = "++++++++++[>+<-]";
     printf("\ntext:%s\n\"%s\"%s\n", color_bright_green, text, color_reset);
+    Parser parser = parser_create(lexer_from_string(text, strlen(text)));
+
+    // Parser parser = parser_create(lexer_from_args_or_stdin(argc, argv));
 
     char* ast_string = malloc(sizeof(char) * 33768);
     ast_string[0] = '\0';
 
-    Parser parser = parser_create(text, strlen(text));
     ExprVec ast = parser_parse(&parser);
     {
         expr_vec_stringify(&ast, ast_string, 0);
@@ -787,7 +43,7 @@ int main(void)
             expr_vec_free(&previous_ast);
         }
         previous_ast = ast;
-        ast = expr_vec_optimize_fold_adjecent(&ast);
+        ast = optimize_fold_adjecent(&ast);
         printf("%sfold_adjecent:%s\n", color_bold, color_reset);
         if (!expr_vec_equal(&ast, &previous_ast)) {
             ast_string[0] = '\0';
@@ -797,7 +53,7 @@ int main(void)
 
         expr_vec_free(&previous_ast);
         previous_ast = ast;
-        ast = expr_vec_optimize_eliminate_negation(&ast);
+        ast = optimize_eliminate_negation(&ast);
         printf("%seliminate_negation:%s\n", color_bold, color_reset);
         if (!expr_vec_equal(&ast, &previous_ast)) {
             ast_string[0] = '\0';
@@ -807,7 +63,7 @@ int main(void)
 
         expr_vec_free(&previous_ast);
         previous_ast = ast;
-        ast = expr_vec_optimize_eliminate_overflow(&ast);
+        ast = optimize_eliminate_overflow(&ast);
         printf("%seliminate_overflow:%s\n", color_bold, color_reset);
         if (!expr_vec_equal(&ast, &previous_ast)) {
             ast_string[0] = '\0';
@@ -817,7 +73,7 @@ int main(void)
 
         expr_vec_free(&previous_ast);
         previous_ast = ast;
-        ast = expr_vec_optimize_replace_zeroing_loops(&ast);
+        ast = optimize_replace_zeroing_loops(&ast);
         printf("%sreplace_zeroing_loops:%s\n", color_bold, color_reset);
         if (!expr_vec_equal(&ast, &previous_ast)) {
             ast_string[0] = '\0';
@@ -835,7 +91,7 @@ int main(void)
     printf("\n%sfinal:%s\n%s\n", color_bold, color_reset, ast_string);
 
     size_t code_size = 33678;
-    uint8_t* code = mmap(
+    void* code = mmap(
         NULL,
         code_size,
         PROT_READ | PROT_WRITE | PROT_EXEC,
@@ -854,13 +110,11 @@ int main(void)
     uint8_t* memory = malloc(30000);
     memset(memory, 0, 30000);
 
-    void (*runnable)(uint8_t* memory) = (void (*)(uint8_t* memory))(void*)code;
-
     printf("\n%scode:%s\n", color_bold, color_reset);
 
     for (size_t y = 0; y < 8; ++y) {
         for (size_t x = 0; x < 8; ++x) {
-            uint8_t v = code[y * 8 + x];
+            uint8_t v = ((uint8_t*)code)[y * 8 + x];
             if (v == 0) {
                 fputs(color_gray, stdout);
             }
@@ -872,6 +126,11 @@ int main(void)
 
     printf("\n%sresult:%s\n", color_bold, color_reset);
 
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wpedantic"
+    void (*runnable)(uint8_t* memory) = (void (*)(uint8_t* memory))code;
+#pragma GCC diagnostic pop
+
     runnable(memory);
 
     printf("\n%smemory:%s\n", color_bold, color_reset);
diff --git a/optimizer.c b/optimizer.c
new file mode 100644
index 0000000..d8e9804
--- /dev/null
+++ b/optimizer.c
@@ -0,0 +1,222 @@
+#include "optimizer.h"
+#include "expr.h"
+
+/*
+ *  fold adjecent
+ *
+ *  A(N) :: { Incr(N) | Decr(N) | Right(N) | Left(N) }
+ *
+ *  [A(N1) A(N2)] -> [A(N1 + N2)]
+ *
+ */
+
+ExprVec optimize_fold_adjecent(const ExprVec* vec)
+{
+    ExprVec exprs;
+    expr_vec_construct(&exprs);
+    if (vec->length == 0) {
+        return exprs;
+    }
+    Expr a = expr_optimize_fold_adjecent(&vec->data[0]);
+    for (size_t i = 1; i < vec->length; ++i) {
+        Expr b = expr_optimize_fold_adjecent(&vec->data[i]);
+        switch (a.type) {
+            case ExprType_Incr:
+            case ExprType_Decr:
+            case ExprType_Left:
+            case ExprType_Right:
+                if (a.type != b.type) {
+                    expr_vec_push(&exprs, a);
+                    a = b;
+                } else {
+                    a.value += b.value;
+                }
+                break;
+            default:
+                expr_vec_push(&exprs, a);
+                a = b;
+        }
+    }
+    expr_vec_push(&exprs, a);
+    return exprs;
+}
+
+Expr expr_optimize_fold_adjecent(const Expr* expr)
+{
+    if (expr->type == ExprType_Loop) {
+        return (Expr) {
+            .type = ExprType_Loop,
+            .exprs = optimize_fold_adjecent(&expr->exprs),
+        };
+    } else {
+        return *expr;
+    }
+}
+
+/*
+ *  eliminate negation
+ *
+ *  A(N), B(N) :: { Incr(N) | Decr(N) | Right(N) | Left(N) }
+ *
+ *  [A(N) B(N)] = []
+ *
+ *  [A(N1) B(N2)] ? N1 == N2 -> []
+ *  [A(N1) B(N2)] ? N1 < N2 -> [B(N2 - N1)]
+ *  [A(N1) B(N2)] ? N1 > N2 -> [A(N1 - N2)]
+ *
+ */
+
+ExprVec optimize_eliminate_negation(const ExprVec* vec)
+{
+    ExprVec exprs;
+    expr_vec_construct(&exprs);
+    if (vec->length == 0) {
+        return exprs;
+    }
+    expr_vec_push(&exprs, expr_optimize_eliminate_negation(&vec->data[0]));
+    for (size_t i = 1; i < vec->length; ++i) {
+        expr_vec_push(&exprs, expr_optimize_eliminate_negation(&vec->data[i]));
+        Expr* a = &exprs.data[i - 1];
+        Expr* b = &exprs.data[i];
+        if (a->type == ExprType_Incr && b->type == ExprType_Decr) {
+            if (a->value > b->value) {
+                a->value -= b->value;
+                expr_vec_pop(&exprs);
+            } else if (a->value < b->value) {
+                *a = (Expr) { .type = ExprType_Decr,
+                              .value = b->value - a->value };
+                expr_vec_pop(&exprs);
+            } else {
+                expr_vec_pop(&exprs);
+                expr_vec_pop(&exprs);
+            }
+        } else if (a->type == ExprType_Decr && b->type == ExprType_Incr) {
+            if (a->value > b->value) {
+                a->value -= b->value;
+                expr_vec_pop(&exprs);
+            } else if (a->value < b->value) {
+                *a = (Expr) { .type = ExprType_Incr,
+                              .value = b->value - a->value };
+                expr_vec_pop(&exprs);
+            } else {
+                expr_vec_pop(&exprs);
+                expr_vec_pop(&exprs);
+            }
+        }
+        if (a->type == ExprType_Left && b->type == ExprType_Right) {
+            if (a->value > b->value) {
+                a->value -= b->value;
+                expr_vec_pop(&exprs);
+            } else if (a->value < b->value) {
+                *a = (Expr) { .type = ExprType_Right,
+                              .value = b->value - a->value };
+                expr_vec_pop(&exprs);
+            } else {
+                expr_vec_pop(&exprs);
+                expr_vec_pop(&exprs);
+            }
+        } else if (a->type == ExprType_Right && b->type == ExprType_Left) {
+            if (a->value > b->value) {
+                a->value -= b->value;
+                expr_vec_pop(&exprs);
+            } else if (a->value < b->value) {
+                *a = (Expr) { .type = ExprType_Left,
+                              .value = b->value - a->value };
+                expr_vec_pop(&exprs);
+            } else {
+                expr_vec_pop(&exprs);
+                expr_vec_pop(&exprs);
+            }
+        }
+    }
+    return exprs;
+}
+
+Expr expr_optimize_eliminate_negation(const Expr* expr)
+{
+    if (expr->type == ExprType_Loop) {
+        return (Expr) {
+            .type = ExprType_Loop,
+            .exprs = optimize_eliminate_negation(&expr->exprs),
+        };
+    } else {
+        return *expr;
+    }
+}
+
+/*
+ *  eliminate overflow
+ *
+ *  A(N) :: { Incr(N) | Decr(N) | Right(N) | Left(N) }
+ *
+ *  N > 255
+ *
+ *  A(N) -> A(N % 256)
+ *
+ */
+
+ExprVec optimize_eliminate_overflow(const ExprVec* vec)
+{
+    ExprVec exprs;
+    expr_vec_construct(&exprs);
+    for (size_t i = 0; i < vec->length; ++i) {
+        expr_vec_push(&exprs, expr_optimize_eliminate_overflow(&vec->data[i]));
+    }
+    return exprs;
+}
+
+Expr expr_optimize_eliminate_overflow(const Expr* expr)
+{
+    if (expr->type == ExprType_Loop) {
+        return (Expr) {
+            .type = ExprType_Loop,
+            .exprs = optimize_eliminate_overflow(&expr->exprs),
+        };
+    } else if (expr->value > 255) {
+        return (Expr) { .type = expr->type, .value = expr->value % 256 };
+    } else {
+        return *expr;
+    }
+}
+
+/*
+ *  replace zeroing loops
+ *
+ *  A(N) :: { Incr(N) | Decr(N) }
+ *
+ *  N % 2 == 1
+ *
+ *  Loop[A(N)] -> Zero
+ *
+ */
+
+ExprVec optimize_replace_zeroing_loops(const ExprVec* vec)
+{
+    ExprVec exprs;
+    expr_vec_construct(&exprs);
+    for (size_t i = 0; i < vec->length; ++i) {
+        expr_vec_push(
+            &exprs, expr_optimize_replace_zeroing_loops(&vec->data[i])
+        );
+    }
+    return exprs;
+}
+
+Expr expr_optimize_replace_zeroing_loops(const Expr* expr)
+{
+    if (expr->type == ExprType_Loop) {
+        if (expr->exprs.length == 1
+            && (expr->exprs.data[0].type == ExprType_Incr
+                || expr->exprs.data[0].type == ExprType_Decr)
+            && expr->exprs.data[0].value % 2 != 0) {
+            return (Expr) { .type = ExprType_Zero };
+        } else {
+            return (Expr) {
+                .type = ExprType_Loop,
+                .exprs = optimize_replace_zeroing_loops(&expr->exprs),
+            };
+        }
+    } else {
+        return *expr;
+    }
+}
diff --git a/optimizer.h b/optimizer.h
new file mode 100644
index 0000000..6ed7c65
--- /dev/null
+++ b/optimizer.h
@@ -0,0 +1,18 @@
+#ifndef OPTIMIZER_H
+#define OPTIMIZER_H
+
+#include "expr.h"
+
+ExprVec optimize_fold_adjecent(const ExprVec* vec);
+Expr expr_optimize_fold_adjecent(const Expr* expr);
+
+ExprVec optimize_eliminate_negation(const ExprVec* vec);
+Expr expr_optimize_eliminate_negation(const Expr* expr);
+
+ExprVec optimize_eliminate_overflow(const ExprVec* vec);
+Expr expr_optimize_eliminate_overflow(const Expr* expr);
+
+ExprVec optimize_replace_zeroing_loops(const ExprVec* vec);
+Expr expr_optimize_replace_zeroing_loops(const Expr* expr);
+
+#endif
diff --git a/parser.c b/parser.c
new file mode 100644
index 0000000..ea31e87
--- /dev/null
+++ b/parser.c
@@ -0,0 +1,169 @@
+#include "parser.h"
+#include <stdlib.h>
+
+Lexer lexer_from_string(const char* text, size_t length)
+{
+    Lexer lexer = (Lexer) {
+        .type = LexerType_String,
+        .current = text[0],
+        .string = {
+            .text = text,
+            .index = 0,
+            .length = length,
+        },
+    };
+    return lexer;
+}
+
+Lexer lexer_from_file(FILE* file)
+{
+    Lexer lexer = (Lexer) {
+        .type = LexerType_File,
+        .current = 1,
+        .file = file,
+    };
+    lexer_step(&lexer);
+    return lexer;
+}
+
+Lexer lexer_from_args_or_stdin(int argc, char** argv)
+{
+    if (argc >= 2) {
+        FILE* file = fopen(argv[1], "r");
+        if (!file) {
+            fprintf(stderr, "panic: could not open file \"%s\"\n", argv[1]);
+            exit(1);
+        }
+        return lexer_from_file(file);
+    } else {
+        return lexer_from_file(stdin);
+    }
+}
+
+bool lexer_done(Lexer* lexer)
+{
+    switch (lexer->type) {
+        case LexerType_String:
+            return lexer->string.index >= lexer->string.length;
+        case LexerType_File:
+            return lexer->current == '\0';
+    }
+    exit(1);
+}
+
+void lexer_step(Lexer* lexer)
+{
+    if (lexer_done(lexer)) {
+        return;
+    }
+    switch (lexer->type) {
+        case LexerType_String:
+            lexer->string.index += 1;
+            lexer->current = lexer->string.text[lexer->string.index];
+            break;
+        case LexerType_File: {
+            int c = fgetc(lexer->file);
+            lexer->current = c != EOF ? (char)c : '\0';
+        } break;
+    }
+}
+
+Token lexer_next(Lexer* lexer)
+{
+    if (lexer_done(lexer)) {
+        return Token_Eof;
+    }
+    switch (lexer->current) {
+        case '+':
+            return (lexer_step(lexer), Token_Plus);
+        case '-':
+            return (lexer_step(lexer), Token_Minus);
+        case '<':
+            return (lexer_step(lexer), Token_LT);
+        case '>':
+            return (lexer_step(lexer), Token_GT);
+        case '.':
+            return (lexer_step(lexer), Token_Dot);
+        case ',':
+            return (lexer_step(lexer), Token_Comma);
+        case '[':
+            return (lexer_step(lexer), Token_LBracket);
+        case ']':
+            return (lexer_step(lexer), Token_RBracket);
+        default:
+            return (lexer_step(lexer), lexer_next(lexer));
+    }
+}
+
+Parser parser_create(Lexer lexer)
+{
+    return (Parser) {
+        .lexer = lexer,
+        .current = lexer_next(&lexer),
+    };
+}
+
+void parser_step(Parser* parser)
+{
+    parser->current = lexer_next(&parser->lexer);
+}
+Expr parser_parse_expr(Parser* parser);
+
+Expr parser_parse_loop(Parser* parser)
+{
+    parser_step(parser);
+    ExprVec exprs;
+    expr_vec_construct(&exprs);
+    while (parser->current != Token_Eof && parser->current != Token_RBracket) {
+        expr_vec_push(&exprs, parser_parse_expr(parser));
+    }
+    if (parser->current != Token_RBracket) {
+        return (Expr) { .type = ExprType_Error };
+    }
+    parser_step(parser);
+    return (Expr) { .type = ExprType_Loop, .exprs = exprs };
+}
+
+Expr parser_parse_expr(Parser* parser)
+{
+    switch (parser->current) {
+        case Token_Plus:
+            return (
+                parser_step(parser),
+                (Expr) { .type = ExprType_Incr, .value = 1 }
+            );
+        case Token_Minus:
+            return (
+                parser_step(parser),
+                (Expr) { .type = ExprType_Decr, .value = 1 }
+            );
+        case Token_LT:
+            return (
+                parser_step(parser),
+                (Expr) { .type = ExprType_Left, .value = 1 }
+            );
+        case Token_GT:
+            return (
+                parser_step(parser),
+                (Expr) { .type = ExprType_Right, .value = 1 }
+            );
+        case Token_Dot:
+            return (parser_step(parser), (Expr) { .type = ExprType_Output });
+        case Token_Comma:
+            return (parser_step(parser), (Expr) { .type = ExprType_Input });
+        case Token_LBracket:
+            return parser_parse_loop(parser);
+        default:
+            return (parser_step(parser), (Expr) { .type = ExprType_Error });
+    }
+}
+
+ExprVec parser_parse(Parser* parser)
+{
+    ExprVec exprs;
+    expr_vec_construct(&exprs);
+    while (parser->current != Token_Eof) {
+        expr_vec_push(&exprs, parser_parse_expr(parser));
+    }
+    return exprs;
+}
diff --git a/parser.h b/parser.h
new file mode 100644
index 0000000..ff820b2
--- /dev/null
+++ b/parser.h
@@ -0,0 +1,55 @@
+#ifndef PARSER_H
+#define PARSER_H
+
+#include "expr.h"
+#include <stdio.h>
+
+typedef enum {
+    Token_Eof,
+    Token_Plus,
+    Token_Minus,
+    Token_LT,
+    Token_GT,
+    Token_Dot,
+    Token_Comma,
+    Token_LBracket,
+    Token_RBracket
+} Token;
+
+typedef enum {
+    LexerType_String,
+    LexerType_File,
+} LexerType;
+
+typedef struct {
+    LexerType type;
+    char current;
+    union {
+        struct {
+            const char* text;
+            size_t index;
+            size_t length;
+        } string;
+        FILE* file;
+    };
+} Lexer;
+
+Lexer lexer_from_string(const char* text, size_t length);
+Lexer lexer_from_file(FILE* file);
+Lexer lexer_from_args_or_stdin(int argc, char** argv);
+bool lexer_done(Lexer* lexer);
+void lexer_step(Lexer* lexer);
+Token lexer_next(Lexer* lexer);
+
+typedef struct {
+    Lexer lexer;
+    Token current;
+} Parser;
+
+Parser parser_create(Lexer lexer);
+void parser_step(Parser* parser);
+Expr parser_parse_loop(Parser* parser);
+Expr parser_parse_expr(Parser* parser);
+ExprVec parser_parse(Parser* parser);
+
+#endif
diff --git a/print.h b/print.h
new file mode 100644
index 0000000..46151a2
--- /dev/null
+++ b/print.h
@@ -0,0 +1,27 @@
+#ifndef COLOR_H
+#define COLOR_H
+
+#define MAYBE_UNUSED __attribute__((unused))
+
+MAYBE_UNUSED static const char* color_reset = "\x1b[0m";
+MAYBE_UNUSED static const char* color_bold = "\x1b[1m";
+
+MAYBE_UNUSED static const char* color_black = "\x1b[30m";
+MAYBE_UNUSED static const char* color_red = "\x1b[31m";
+MAYBE_UNUSED static const char* color_green = "\x1b[32m";
+MAYBE_UNUSED static const char* color_yellow = "\x1b[33m";
+MAYBE_UNUSED static const char* color_blue = "\x1b[34m";
+MAYBE_UNUSED static const char* color_magenta = "\x1b[35m";
+MAYBE_UNUSED static const char* color_cyan = "\x1b[36m";
+MAYBE_UNUSED static const char* color_bright_gray = "\x1b[37m";
+
+MAYBE_UNUSED static const char* color_gray = "\x1b[90m";
+MAYBE_UNUSED static const char* color_bright_red = "\x1b[91m";
+MAYBE_UNUSED static const char* color_bright_green = "\x1b[92m";
+MAYBE_UNUSED static const char* color_bright_yellow = "\x1b[93m";
+MAYBE_UNUSED static const char* color_bright_blue = "\x1b[94m";
+MAYBE_UNUSED static const char* color_bright_magenta = "\x1b[95m";
+MAYBE_UNUSED static const char* color_bright_cyan = "\x1b[96m";
+MAYBE_UNUSED static const char* color_white = "\x1b[97m";
+
+#endif
diff --git a/runtime.c b/runtime.c
new file mode 100644
index 0000000..a04ce90
--- /dev/null
+++ b/runtime.c
@@ -0,0 +1,7 @@
+#include "runtime.h"
+#include <stdint.h>
+#include <stdio.h>
+
+uint8_t get_char(void) { return (uint8_t)fgetc(stdin); }
+
+void put_char(uint8_t v) { fputc(v, stdout); }
diff --git a/runtime.h b/runtime.h
new file mode 100644
index 0000000..5ad0369
--- /dev/null
+++ b/runtime.h
@@ -0,0 +1,9 @@
+#ifndef RUNTIME_H
+#define RUNTIME_H
+
+#include <stdint.h>
+
+uint8_t get_char(void);
+void put_char(uint8_t v);
+
+#endif