diff --git a/Makefile b/Makefile
index 5939e7d..8aafc0b 100644
--- a/Makefile
+++ b/Makefile
@@ -7,6 +7,7 @@ CXX = $(TARGET)clang++
 SRC = main.cpp
 SRC += lexer.cpp
 SRC += ast.cpp
+SRC += parser.cpp
 OBJ = $(patsubst %.cpp,%.o,$(SRC))
 DEP = $(patsubst %.cpp,%.d,$(SRC))
 
diff --git a/ast.cpp b/ast.cpp
index 6d8cf8b..8dbfc4f 100644
--- a/ast.cpp
+++ b/ast.cpp
@@ -4,7 +4,7 @@ namespace dsp {
 
 void ast_printer_t::visit(const unary_t * unary) const
 {
-  parenthesize((unary->oper).lexeme, unary->expr);
+  parenthesize((unary->oper).lexeme, unary->right);
 }
 
 void ast_printer_t::visit(const binary_t * binary) const
diff --git a/build_radix_tree.py b/build_radix_tree.py
index 089e4e8..e1c4648 100644
--- a/build_radix_tree.py
+++ b/build_radix_tree.py
@@ -1,3 +1,5 @@
+import sys
+
 def build_radix_tree(ops: list[str]) -> dict:
     root = dict()
     for op in ops:
@@ -62,38 +64,123 @@ def print_keyword_func(root):
     p()
     p("}")
 
-from pprint import pprint
-d = build_radix_tree([
-    "alh",
-    "all",
-    "alu",
-    "m0",  "m1",  "m2", "m3",
-    "mc0", "mc1", "mc2", "mc3",
-    "mul",
-    "nop",
-    "and",
-    "or",
-    "xor",
-    "add",
-    "sub",
+
+alu_keywords = [
     "ad2",
-    "sr",
-    "rr",
-    "sl",
+    "add",
+    "and",
+    "nop",
+    "or",
     "rl",
     "rl8",
+    "rr",
+    "sl",
+    "sr",
+    "sub",
+    "xor",
+]
+
+x_bus_keywords = [
+    "mov", # Mn, MCn
+    "x",
+    "p",
+    "mul",
+]
+
+mn = ["m0", "m1", "m2", "m3"]
+mcn = ["mc0", "mc1", "mc2", "mc3"]
+
+y_bus_keywords = [
+    "mov", # Mn, MCn
     "clr",
-    "mov",
+    "y",
+    "a",
+    "alu",
+]
+
+d1_bus_keywords = [
+    "mov", # MCn
+    "alh",
+    "all",
+]
+
+reg_keywords = [
+    "rx",
+    "pl",
+    "ra0",
+    "wa0",
+    "lop",
+    "top",
+]
+
+cond_keywords = [
+    "z",
+    "nz",
+    "s",
+    "ns",
+    "c",
+    "nc",
+    "t0",
+    "nt0",
+    "zs",
+    "nzs",
+]
+
+move_immediate_keywords = [
     "mvi",
+]
+
+dma_keywords = [
     "dma",
     "dmah",
+    "d0",
+    "prg",
+]
+
+jmp_keywords = [
     "jmp",
+]
+
+loop_keywords = [
     "btm",
     "lps",
+]
+
+halt_keywords = [
     "end",
     "endi",
+]
+
+directive_keywords = [
     "equ",
     "org",
-    "ends",
-])
-print_keyword_func(d)
+]
+
+keywords = sorted(set([
+    *alu_keywords,
+    *x_bus_keywords,
+    *mn,
+    *mcn,
+    *y_bus_keywords,
+    *d1_bus_keywords,
+    *reg_keywords,
+    *cond_keywords,
+    *move_immediate_keywords,
+    *dma_keywords,
+    *jmp_keywords,
+    *loop_keywords,
+    *halt_keywords,
+    *directive_keywords,
+]))
+
+if sys.argv[1] == 'hpp':
+    d = build_radix_tree(keywords)
+    print_keyword_func(d)
+elif sys.argv[1] == 'enum_inc':
+    for k in keywords:
+        print(f"_{k},")
+elif sys.argv[1] == 'case_inc':
+    for k in keywords:
+        print(f'case _{k.ljust(4, " ")}       : return os << "{k.upper()}";')
+else:
+    assert False, sys.argv
diff --git a/expr.hpp b/expr.hpp
index d425858..0d8318d 100644
--- a/expr.hpp
+++ b/expr.hpp
@@ -1,3 +1,5 @@
+#pragma once
+
 #include <string>
 
 #include "token.hpp"
diff --git a/keyword.case_inc b/keyword.case_inc
new file mode 100644
index 0000000..d9d9b71
--- /dev/null
+++ b/keyword.case_inc
@@ -0,0 +1,58 @@
+case _a          : return os << "A";
+case _ad2        : return os << "AD2";
+case _add        : return os << "ADD";
+case _alh        : return os << "ALH";
+case _all        : return os << "ALL";
+case _alu        : return os << "ALU";
+case _and        : return os << "AND";
+case _btm        : return os << "BTM";
+case _c          : return os << "C";
+case _clr        : return os << "CLR";
+case _d0         : return os << "D0";
+case _dma        : return os << "DMA";
+case _dmah       : return os << "DMAH";
+case _end        : return os << "END";
+case _endi       : return os << "ENDI";
+case _equ        : return os << "EQU";
+case _jmp        : return os << "JMP";
+case _lop        : return os << "LOP";
+case _lps        : return os << "LPS";
+case _m0         : return os << "M0";
+case _m1         : return os << "M1";
+case _m2         : return os << "M2";
+case _m3         : return os << "M3";
+case _mc0        : return os << "MC0";
+case _mc1        : return os << "MC1";
+case _mc2        : return os << "MC2";
+case _mc3        : return os << "MC3";
+case _mov        : return os << "MOV";
+case _mul        : return os << "MUL";
+case _mvi        : return os << "MVI";
+case _nc         : return os << "NC";
+case _nop        : return os << "NOP";
+case _ns         : return os << "NS";
+case _nt0        : return os << "NT0";
+case _nz         : return os << "NZ";
+case _nzs        : return os << "NZS";
+case _or         : return os << "OR";
+case _org        : return os << "ORG";
+case _p          : return os << "P";
+case _pl         : return os << "PL";
+case _prg        : return os << "PRG";
+case _ra0        : return os << "RA0";
+case _rl         : return os << "RL";
+case _rl8        : return os << "RL8";
+case _rr         : return os << "RR";
+case _rx         : return os << "RX";
+case _s          : return os << "S";
+case _sl         : return os << "SL";
+case _sr         : return os << "SR";
+case _sub        : return os << "SUB";
+case _t0         : return os << "T0";
+case _top        : return os << "TOP";
+case _wa0        : return os << "WA0";
+case _x          : return os << "X";
+case _xor        : return os << "XOR";
+case _y          : return os << "Y";
+case _z          : return os << "Z";
+case _zs         : return os << "ZS";
diff --git a/keyword.enum_inc b/keyword.enum_inc
new file mode 100644
index 0000000..cba7772
--- /dev/null
+++ b/keyword.enum_inc
@@ -0,0 +1,58 @@
+_a,
+_ad2,
+_add,
+_alh,
+_all,
+_alu,
+_and,
+_btm,
+_c,
+_clr,
+_d0,
+_dma,
+_dmah,
+_end,
+_endi,
+_equ,
+_jmp,
+_lop,
+_lps,
+_m0,
+_m1,
+_m2,
+_m3,
+_mc0,
+_mc1,
+_mc2,
+_mc3,
+_mov,
+_mul,
+_mvi,
+_nc,
+_nop,
+_ns,
+_nt0,
+_nz,
+_nzs,
+_or,
+_org,
+_p,
+_pl,
+_prg,
+_ra0,
+_rl,
+_rl8,
+_rr,
+_rx,
+_s,
+_sl,
+_sr,
+_sub,
+_t0,
+_top,
+_wa0,
+_x,
+_xor,
+_y,
+_z,
+_zs,
diff --git a/keyword.hpp b/keyword.hpp
index 0d057e5..726668b 100644
--- a/keyword.hpp
+++ b/keyword.hpp
@@ -15,8 +15,23 @@ find(const std::string_view s)
   switch (s[ix++]) {
   case 'A': [[fallthrough]];
   case 'a':
-    if (ix < s.length()) {
+    if (ix == s.length()) return { token_t::type_t::_a };
+    else {
       switch (s[ix++]) {
+      case 'D': [[fallthrough]];
+      case 'd':
+        if (ix < s.length()) {
+          switch (s[ix++]) {
+          case '2':
+            if (ix == s.length()) return { token_t::type_t::_ad2 };
+            break;
+          case 'D': [[fallthrough]];
+          case 'd':
+            if (ix == s.length()) return { token_t::type_t::_add };
+            break;
+          }
+        }
+        break;
       case 'L': [[fallthrough]];
       case 'l':
         if (ix < s.length()) {
@@ -47,16 +62,152 @@ find(const std::string_view s)
           }
         }
         break;
-      case 'D': [[fallthrough]];
-      case 'd':
+      }
+    }
+    break;
+  case 'B': [[fallthrough]];
+  case 'b':
+    if (ix < s.length()) {
+      switch (s[ix++]) {
+      case 'T': [[fallthrough]];
+      case 't':
+        if (ix < s.length()) {
+          switch (s[ix++]) {
+          case 'M': [[fallthrough]];
+          case 'm':
+            if (ix == s.length()) return { token_t::type_t::_btm };
+            break;
+          }
+        }
+        break;
+      }
+    }
+    break;
+  case 'C': [[fallthrough]];
+  case 'c':
+    if (ix == s.length()) return { token_t::type_t::_c };
+    else {
+      switch (s[ix++]) {
+      case 'L': [[fallthrough]];
+      case 'l':
+        if (ix < s.length()) {
+          switch (s[ix++]) {
+          case 'R': [[fallthrough]];
+          case 'r':
+            if (ix == s.length()) return { token_t::type_t::_clr };
+            break;
+          }
+        }
+        break;
+      }
+    }
+    break;
+  case 'D': [[fallthrough]];
+  case 'd':
+    if (ix < s.length()) {
+      switch (s[ix++]) {
+      case '0':
+        if (ix == s.length()) return { token_t::type_t::_d0 };
+        break;
+      case 'M': [[fallthrough]];
+      case 'm':
+        if (ix < s.length()) {
+          switch (s[ix++]) {
+          case 'A': [[fallthrough]];
+          case 'a':
+            if (ix == s.length()) return { token_t::type_t::_dma };
+            else {
+              switch (s[ix++]) {
+              case 'H': [[fallthrough]];
+              case 'h':
+                if (ix == s.length()) return { token_t::type_t::_dmah };
+                break;
+              }
+            }
+            break;
+          }
+        }
+        break;
+      }
+    }
+    break;
+  case 'E': [[fallthrough]];
+  case 'e':
+    if (ix < s.length()) {
+      switch (s[ix++]) {
+      case 'N': [[fallthrough]];
+      case 'n':
         if (ix < s.length()) {
           switch (s[ix++]) {
           case 'D': [[fallthrough]];
           case 'd':
-            if (ix == s.length()) return { token_t::type_t::_add };
+            if (ix == s.length()) return { token_t::type_t::_end };
+            else {
+              switch (s[ix++]) {
+              case 'I': [[fallthrough]];
+              case 'i':
+                if (ix == s.length()) return { token_t::type_t::_endi };
+                break;
+              }
+            }
             break;
-          case '2':
-            if (ix == s.length()) return { token_t::type_t::_ad2 };
+          }
+        }
+        break;
+      case 'Q': [[fallthrough]];
+      case 'q':
+        if (ix < s.length()) {
+          switch (s[ix++]) {
+          case 'U': [[fallthrough]];
+          case 'u':
+            if (ix == s.length()) return { token_t::type_t::_equ };
+            break;
+          }
+        }
+        break;
+      }
+    }
+    break;
+  case 'J': [[fallthrough]];
+  case 'j':
+    if (ix < s.length()) {
+      switch (s[ix++]) {
+      case 'M': [[fallthrough]];
+      case 'm':
+        if (ix < s.length()) {
+          switch (s[ix++]) {
+          case 'P': [[fallthrough]];
+          case 'p':
+            if (ix == s.length()) return { token_t::type_t::_jmp };
+            break;
+          }
+        }
+        break;
+      }
+    }
+    break;
+  case 'L': [[fallthrough]];
+  case 'l':
+    if (ix < s.length()) {
+      switch (s[ix++]) {
+      case 'O': [[fallthrough]];
+      case 'o':
+        if (ix < s.length()) {
+          switch (s[ix++]) {
+          case 'P': [[fallthrough]];
+          case 'p':
+            if (ix == s.length()) return { token_t::type_t::_lop };
+            break;
+          }
+        }
+        break;
+      case 'P': [[fallthrough]];
+      case 'p':
+        if (ix < s.length()) {
+          switch (s[ix++]) {
+          case 'S': [[fallthrough]];
+          case 's':
+            if (ix == s.length()) return { token_t::type_t::_lps };
             break;
           }
         }
@@ -99,17 +250,6 @@ find(const std::string_view s)
           }
         }
         break;
-      case 'U': [[fallthrough]];
-      case 'u':
-        if (ix < s.length()) {
-          switch (s[ix++]) {
-          case 'L': [[fallthrough]];
-          case 'l':
-            if (ix == s.length()) return { token_t::type_t::_mul };
-            break;
-          }
-        }
-        break;
       case 'O': [[fallthrough]];
       case 'o':
         if (ix < s.length()) {
@@ -121,6 +261,17 @@ find(const std::string_view s)
           }
         }
         break;
+      case 'U': [[fallthrough]];
+      case 'u':
+        if (ix < s.length()) {
+          switch (s[ix++]) {
+          case 'L': [[fallthrough]];
+          case 'l':
+            if (ix == s.length()) return { token_t::type_t::_mul };
+            break;
+          }
+        }
+        break;
       case 'V': [[fallthrough]];
       case 'v':
         if (ix < s.length()) {
@@ -139,6 +290,10 @@ find(const std::string_view s)
   case 'n':
     if (ix < s.length()) {
       switch (s[ix++]) {
+      case 'C': [[fallthrough]];
+      case 'c':
+        if (ix == s.length()) return { token_t::type_t::_nc };
+        break;
       case 'O': [[fallthrough]];
       case 'o':
         if (ix < s.length()) {
@@ -150,6 +305,32 @@ find(const std::string_view s)
           }
         }
         break;
+      case 'S': [[fallthrough]];
+      case 's':
+        if (ix == s.length()) return { token_t::type_t::_ns };
+        break;
+      case 'T': [[fallthrough]];
+      case 't':
+        if (ix < s.length()) {
+          switch (s[ix++]) {
+          case '0':
+            if (ix == s.length()) return { token_t::type_t::_nt0 };
+            break;
+          }
+        }
+        break;
+      case 'Z': [[fallthrough]];
+      case 'z':
+        if (ix == s.length()) return { token_t::type_t::_nz };
+        else {
+          switch (s[ix++]) {
+          case 'S': [[fallthrough]];
+          case 's':
+            if (ix == s.length()) return { token_t::type_t::_nzs };
+            break;
+          }
+        }
+        break;
       }
     }
     break;
@@ -172,9 +353,134 @@ find(const std::string_view s)
       }
     }
     break;
+  case 'P': [[fallthrough]];
+  case 'p':
+    if (ix == s.length()) return { token_t::type_t::_p };
+    else {
+      switch (s[ix++]) {
+      case 'L': [[fallthrough]];
+      case 'l':
+        if (ix == s.length()) return { token_t::type_t::_pl };
+        break;
+      case 'R': [[fallthrough]];
+      case 'r':
+        if (ix < s.length()) {
+          switch (s[ix++]) {
+          case 'G': [[fallthrough]];
+          case 'g':
+            if (ix == s.length()) return { token_t::type_t::_prg };
+            break;
+          }
+        }
+        break;
+      }
+    }
+    break;
+  case 'R': [[fallthrough]];
+  case 'r':
+    if (ix < s.length()) {
+      switch (s[ix++]) {
+      case 'A': [[fallthrough]];
+      case 'a':
+        if (ix < s.length()) {
+          switch (s[ix++]) {
+          case '0':
+            if (ix == s.length()) return { token_t::type_t::_ra0 };
+            break;
+          }
+        }
+        break;
+      case 'L': [[fallthrough]];
+      case 'l':
+        if (ix == s.length()) return { token_t::type_t::_rl };
+        else {
+          switch (s[ix++]) {
+          case '8':
+            if (ix == s.length()) return { token_t::type_t::_rl8 };
+            break;
+          }
+        }
+        break;
+      case 'R': [[fallthrough]];
+      case 'r':
+        if (ix == s.length()) return { token_t::type_t::_rr };
+        break;
+      case 'X': [[fallthrough]];
+      case 'x':
+        if (ix == s.length()) return { token_t::type_t::_rx };
+        break;
+      }
+    }
+    break;
+  case 'S': [[fallthrough]];
+  case 's':
+    if (ix == s.length()) return { token_t::type_t::_s };
+    else {
+      switch (s[ix++]) {
+      case 'L': [[fallthrough]];
+      case 'l':
+        if (ix == s.length()) return { token_t::type_t::_sl };
+        break;
+      case 'R': [[fallthrough]];
+      case 'r':
+        if (ix == s.length()) return { token_t::type_t::_sr };
+        break;
+      case 'U': [[fallthrough]];
+      case 'u':
+        if (ix < s.length()) {
+          switch (s[ix++]) {
+          case 'B': [[fallthrough]];
+          case 'b':
+            if (ix == s.length()) return { token_t::type_t::_sub };
+            break;
+          }
+        }
+        break;
+      }
+    }
+    break;
+  case 'T': [[fallthrough]];
+  case 't':
+    if (ix < s.length()) {
+      switch (s[ix++]) {
+      case '0':
+        if (ix == s.length()) return { token_t::type_t::_t0 };
+        break;
+      case 'O': [[fallthrough]];
+      case 'o':
+        if (ix < s.length()) {
+          switch (s[ix++]) {
+          case 'P': [[fallthrough]];
+          case 'p':
+            if (ix == s.length()) return { token_t::type_t::_top };
+            break;
+          }
+        }
+        break;
+      }
+    }
+    break;
+  case 'W': [[fallthrough]];
+  case 'w':
+    if (ix < s.length()) {
+      switch (s[ix++]) {
+      case 'A': [[fallthrough]];
+      case 'a':
+        if (ix < s.length()) {
+          switch (s[ix++]) {
+          case '0':
+            if (ix == s.length()) return { token_t::type_t::_wa0 };
+            break;
+          }
+        }
+        break;
+      }
+    }
+    break;
   case 'X': [[fallthrough]];
   case 'x':
-    if (ix < s.length()) {
+    if (ix == s.length()) return { token_t::type_t::_x };
+    else {
       switch (s[ix++]) {
       case 'O': [[fallthrough]];
       case 'o':
@@ -190,189 +496,18 @@ find(const std::string_view s)
       }
     }
     break;
-  case 'S': [[fallthrough]];
-  case 's':
-    if (ix < s.length()) {
-      switch (s[ix++]) {
-      case 'U': [[fallthrough]];
-      case 'u':
-        if (ix < s.length()) {
-          switch (s[ix++]) {
-          case 'B': [[fallthrough]];
-          case 'b':
-            if (ix == s.length()) return { token_t::type_t::_sub };
-            break;
-          }
-        }
-        break;
-      case 'R': [[fallthrough]];
-      case 'r':
-        if (ix == s.length()) return { token_t::type_t::_sr };
-        break;
-      case 'L': [[fallthrough]];
-      case 'l':
-        if (ix == s.length()) return { token_t::type_t::_sl };
-        break;
-      }
-    }
+  case 'Y': [[fallthrough]];
+  case 'y':
+    if (ix == s.length()) return { token_t::type_t::_y };
     break;
-  case 'R': [[fallthrough]];
-  case 'r':
-    if (ix < s.length()) {
+  case 'Z': [[fallthrough]];
+  case 'z':
+    if (ix == s.length()) return { token_t::type_t::_z };
+    else {
       switch (s[ix++]) {
-      case 'R': [[fallthrough]];
-      case 'r':
-        if (ix == s.length()) return { token_t::type_t::_rr };
-        break;
-      case 'L': [[fallthrough]];
-      case 'l':
-        if (ix == s.length()) return { token_t::type_t::_rl };
-        else {
-          switch (s[ix++]) {
-          case '8':
-            if (ix == s.length()) return { token_t::type_t::_rl8 };
-            break;
-          }
-        }
-        break;
-      }
-    }
-    break;
-  case 'C': [[fallthrough]];
-  case 'c':
-    if (ix < s.length()) {
-      switch (s[ix++]) {
-      case 'L': [[fallthrough]];
-      case 'l':
-        if (ix < s.length()) {
-          switch (s[ix++]) {
-          case 'R': [[fallthrough]];
-          case 'r':
-            if (ix == s.length()) return { token_t::type_t::_clr };
-            break;
-          }
-        }
-        break;
-      }
-    }
-    break;
-  case 'D': [[fallthrough]];
-  case 'd':
-    if (ix < s.length()) {
-      switch (s[ix++]) {
-      case 'M': [[fallthrough]];
-      case 'm':
-        if (ix < s.length()) {
-          switch (s[ix++]) {
-          case 'A': [[fallthrough]];
-          case 'a':
-            if (ix == s.length()) return { token_t::type_t::_dma };
-            else {
-              switch (s[ix++]) {
-              case 'H': [[fallthrough]];
-              case 'h':
-                if (ix == s.length()) return { token_t::type_t::_dmah };
-                break;
-              }
-            }
-            break;
-          }
-        }
-        break;
-      }
-    }
-    break;
-  case 'J': [[fallthrough]];
-  case 'j':
-    if (ix < s.length()) {
-      switch (s[ix++]) {
-      case 'M': [[fallthrough]];
-      case 'm':
-        if (ix < s.length()) {
-          switch (s[ix++]) {
-          case 'P': [[fallthrough]];
-          case 'p':
-            if (ix == s.length()) return { token_t::type_t::_jmp };
-            break;
-          }
-        }
-        break;
-      }
-    }
-    break;
-  case 'B': [[fallthrough]];
-  case 'b':
-    if (ix < s.length()) {
-      switch (s[ix++]) {
-      case 'T': [[fallthrough]];
-      case 't':
-        if (ix < s.length()) {
-          switch (s[ix++]) {
-          case 'M': [[fallthrough]];
-          case 'm':
-            if (ix == s.length()) return { token_t::type_t::_btm };
-            break;
-          }
-        }
-        break;
-      }
-    }
-    break;
-  case 'L': [[fallthrough]];
-  case 'l':
-    if (ix < s.length()) {
-      switch (s[ix++]) {
-      case 'P': [[fallthrough]];
-      case 'p':
-        if (ix < s.length()) {
-          switch (s[ix++]) {
-          case 'S': [[fallthrough]];
-          case 's':
-            if (ix == s.length()) return { token_t::type_t::_lps };
-            break;
-          }
-        }
-        break;
-      }
-    }
-    break;
-  case 'E': [[fallthrough]];
-  case 'e':
-    if (ix < s.length()) {
-      switch (s[ix++]) {
-      case 'N': [[fallthrough]];
-      case 'n':
-        if (ix < s.length()) {
-          switch (s[ix++]) {
-          case 'D': [[fallthrough]];
-          case 'd':
-            if (ix == s.length()) return { token_t::type_t::_end };
-            else {
-              switch (s[ix++]) {
-              case 'I': [[fallthrough]];
-              case 'i':
-                if (ix == s.length()) return { token_t::type_t::_endi };
-                break;
-              case 'S': [[fallthrough]];
-              case 's':
-                if (ix == s.length()) return { token_t::type_t::_ends };
-                break;
-              }
-            }
-            break;
-          }
-        }
-        break;
-      case 'Q': [[fallthrough]];
-      case 'q':
-        if (ix < s.length()) {
-          switch (s[ix++]) {
-          case 'U': [[fallthrough]];
-          case 'u':
-            if (ix == s.length()) return { token_t::type_t::_equ };
-            break;
-          }
-        }
+      case 'S': [[fallthrough]];
+      case 's':
+        if (ix == s.length()) return { token_t::type_t::_zs };
         break;
       }
     }
diff --git a/lexer.cpp b/lexer.cpp
index 8deb0d3..1f69039 100644
--- a/lexer.cpp
+++ b/lexer.cpp
@@ -139,7 +139,7 @@ token_t lexer_t::_identifier()
   else         return {pos, token_t::identifier, lexeme()};
 }
 
-std::optional<token_t> lexer_t::scan_token()
+std::optional<token_t> lexer_t::lex_token()
 {
   using enum token_t::type_t;
 
@@ -215,4 +215,17 @@ std::optional<token_t> lexer_t::scan_token()
   __builtin_unreachable();
 }
 
+std::vector<token_t> lexer_t::lex_tokens()
+{
+  std::vector<token_t> tokens;
+
+  while (true) {
+    std::optional<token_t> token_o = lex_token();
+    if (!token_o) continue;
+    tokens.push_back(*token_o);
+    if (token_o->type == token_t::eof) break;
+  }
+  return tokens;
+}
+
 }
diff --git a/lexer.hpp b/lexer.hpp
index 0665962..42f0618 100644
--- a/lexer.hpp
+++ b/lexer.hpp
@@ -2,6 +2,7 @@
 
 #include <string_view>
 #include <optional>
+#include <vector>
 
 #include "token.hpp"
 
@@ -19,7 +20,8 @@ struct lexer_t {
     : source(source), start_ix(0), current_ix(0), pos{ .line = 1, .col = 0 }
   { }
 
-  std::optional<token_t> scan_token();
+  std::optional<token_t> lex_token();
+  std::vector<token_t> lex_tokens();
 
 private:
   bool at_end_p();
diff --git a/lexer_iterator.cpp b/lexer_iterator.cpp
new file mode 100644
index 0000000..8c2daa0
--- /dev/null
+++ b/lexer_iterator.cpp
@@ -0,0 +1,35 @@
+#include "lexer.hpp"
+#include "token.hpp"
+
+namespace dsp {
+
+struct lexer_iterator_t
+{
+  token_t previous_token;
+  token_t current_token;
+  lexer_t& lexer;
+
+  lexer_iterator_t(lexer_t& lexer)
+    : lexer(lexer), previous_token(lexer.scan_token()), current_token(previous_token)
+  {
+  }
+
+  token_t& advance()
+  {
+    previous_token = current_token;
+    current_token = lexer.scan_token();
+    return previous_token;
+  }
+
+  token_t& peek()
+  {
+    return current_token;
+  }
+
+  token_t& previous()
+  {
+    return previous_token;
+  }
+};
+
+}
diff --git a/main.cpp b/main.cpp
index 544e9ac..053d9db 100644
--- a/main.cpp
+++ b/main.cpp
@@ -5,6 +5,7 @@
 #include "lexer.hpp"
 #include "token.hpp"
 #include "ast.hpp"
+#include "parser.hpp"
 
 namespace dsp {
 
@@ -12,28 +13,18 @@ bool had_error = false;
 
 }
 
-static void print()
-{
-  dsp::literal_t l(56);
-  std::string_view s("-");
-  dsp::token_t t({0, 0}, dsp::token_t::minus, s);
-  dsp::unary_t a(t, &l);
-  dsp::ast_printer_t p(std::cout);
-  p.visit(&a);
-}
-
 static void run(std::string source)
 {
   using namespace dsp;
 
-  std::string_view buf {source};
-  lexer_t lexer {buf};
-  while (std::optional<token_t> token_o = lexer.scan_token()) {
-    std::cout << *token_o << std::endl;
-    if (token_o->type == token_t::type_t::eof) {
-      break;
-    }
-  }
+  std::string_view buf(source);
+  lexer_t lexer(buf);
+  std::vector<token_t> tokens = lexer.lex_tokens();
+  parser_t parser(tokens);
+  expr_t * expr = parser.expression();
+  dsp::ast_printer_t p(std::cout);
+  expr->accept(&p);
+  std::cout << std::endl << std::flush;
 }
 
 static void run_prompt()
@@ -67,7 +58,6 @@ static int run_file(char const * const filename)
 
 int main(const int argc, char const * const argv[])
 {
-  print();
   switch (argc) {
   case 1: run_prompt(); return dsp::had_error;
   case 2: return run_file(argv[1]);
diff --git a/token.hpp b/token.hpp
index 6a7e184..a36b841 100644
--- a/token.hpp
+++ b/token.hpp
@@ -45,47 +45,12 @@ struct token_t {
     string,
     number,
 
-    // keywords
-    _alh,
-    _all,
-    _alu,
-    _m0,
-    _m1,
-    _m2,
-    _m3,
-    _mc0,
-    _mc1,
-    _mc2,
-    _mc3,
-    _mul,
-    _nop,
-    _and,
-    _or,
-    _xor,
-    _add,
-    _sub,
-    _ad2,
-    _sr,
-    _rr,
-    _sl,
-    _rl,
-    _rl8,
-    _clr,
-    _mov,
-    _mvi,
-    _dma,
-    _dmah,
-    _jmp,
-    _btm,
-    _lps,
-    _end,
-    _endi,
-    _equ,
-    _org,
-    _ends,
-
+    // ends
     eof,
     eol,
+
+    // keywords
+    #include "keyword.enum_inc"
   };
 
   using literal_t = std::variant<std::monostate, num_type>;
@@ -133,44 +98,8 @@ struct token_t {
     case string       : return os << "STRING";
     case number       : return os << "NUMBER";
 
-      // keywords
-    case _alh         : return os << "ALH";
-    case _all         : return os << "ALL";
-    case _alu         : return os << "ALU";
-    case _m0          : return os << "M0";
-    case _m1          : return os << "M1";
-    case _m2          : return os << "M2";
-    case _m3          : return os << "M3";
-    case _mc0         : return os << "MC0";
-    case _mc1         : return os << "MC1";
-    case _mc2         : return os << "MC2";
-    case _mc3         : return os << "MC3";
-    case _mul         : return os << "MUL";
-    case _nop         : return os << "NOP";
-    case _and         : return os << "AND";
-    case _or          : return os << "OR";
-    case _xor         : return os << "XOR";
-    case _add         : return os << "ADD";
-    case _sub         : return os << "SUB";
-    case _ad2         : return os << "AD2";
-    case _sr          : return os << "SR";
-    case _rr          : return os << "RR";
-    case _sl          : return os << "SL";
-    case _rl          : return os << "RL";
-    case _rl8         : return os << "RL8";
-    case _clr         : return os << "CLR";
-    case _mov         : return os << "MOV";
-    case _mvi         : return os << "MVI";
-    case _dma         : return os << "DMA";
-    case _dmah        : return os << "DMAH";
-    case _jmp         : return os << "JMP";
-    case _btm         : return os << "BTM";
-    case _lps         : return os << "LPS";
-    case _end         : return os << "END";
-    case _endi        : return os << "ENDI";
-    case _equ         : return os << "EQU";
-    case _org         : return os << "ORG";
-    case _ends        : return os << "ENDS";
+    // keywords
+    #include "keyword.case_inc"
 
     case eof          : return os << "EOF";
     case eol          : return os << "EOL";