diff --git a/src/lexer.h b/src/lexer.h
new file mode 100644
index 0000000..b5f80c4
--- /dev/null
+++ b/src/lexer.h
@@ -0,0 +1,51 @@
+#ifndef _LEXER_H
+#define _LEXER_H
+
+#include "types.h"
+
+/*
+  Code parser state
+*/
+typedef enum {
+  PSTART,
+  PEXPR,
+  PARGS,
+  PINSTR
+} ps_t;
+
+/*
+  Lexer (and parser) structure
+*/
+typedef struct {
+  char *          input;
+  char *          last; // input before NextToken
+  char *          next;
+  index_t         line; // line number
+  token_t         token;
+  number_t        x;
+  index_t         ix;
+  token_t         type;
+  char            name[MAXNAMELEN+1];
+  char            *arg;
+  index_t         arglen;
+  ps_t            ps; 
+  int             argN;
+  token_t         lasttoken;
+  token_t         uptoken; // which token, e.g. CCALL, calls compileexpr
+#if HAS_FUNC > 0
+  char            fun[MAXNAMELEN+1];  // function name
+  index_t         fp[2];     // for local variables stored on the stack
+  index_t         level;    // scope nesting level, basically we have only 0 (top-level) and 1 (function) 
+#endif
+#if PROFILE>0
+  index_t         ntoken;
+#endif
+} lexer_t;
+
+void LookAheadToken(lexer_t *lex);
+void SkipToken (lexer_t *lex);
+void NextToken (lexer_t *lex);
+void LexerInit(lexer_t *L);
+void LexerSetup(lexer_t *lex, char * input);
+
+#endif