let regexp blanks = blank+
let regexp num = digit+
let regexp tex_token = '\\' alpha+
-let regexp symbol = symbol_char+
+let regexp symbol = symbol_char
let regexp ident_cont = alpha | num | '_' | '\''
let regexp ident_cont' = ident_cont | tex_token
let regexp ident = (alpha ident_cont*) | ('_' ident_cont+)