add test file for the lexer_generator

src/test_lexer.ml

+open E_regexp
+open Lexer_generator
+open Batteries
+open Utils
+open Symbols
+
+let () =
+  let lowercase_letters = "abcdefghijklmnopqrstuvwxyz" in
+  let uppercase_letters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" in
+  let digits = "0123456789" in
+  let other_characters = "?!=<>_ ;,{}()[]-+*/%\n\t" in
+  let alphabet = char_list_of_string (lowercase_letters ^ uppercase_letters ^ digits ^ other_characters) in
+  let letter_regexp = char_range (char_list_of_string (uppercase_letters ^ lowercase_letters)) in
+  let digit_regexp = char_range (char_list_of_string digits) in
+  let keyword_regexp s = str_regexp (char_list_of_string s) in
+  let regexp_list = [
+    (keyword_regexp "while",    fun s -> Some (SYM_WHILE));
+    (keyword_regexp "if",    fun s -> Some (SYM_IF));
+  ] in
+
+  List.iteri
+    (fun i (rg, _) -> Printf.printf "%d: %s\n" i (string_of_regexp rg))
+    regexp_list;
+
+  let nfa = nfa_of_list_regexp regexp_list in
+
+  Printf.printf "%s\n" (nfa_to_string nfa);
+
+  let oc = open_out "/tmp/nfa.dot" in
+  nfa_to_dot oc nfa;
+  close_out oc;
+
+  let dfa = dfa_of_nfa nfa in
+  let oc = open_out "/tmp/dfa.dot" in
+  dfa_to_dot oc dfa alphabet;
+  close_out oc;
+
+