Anyone able to help with ocaml programming?

Lexical Analysis of LISP: The lexer will be a function which takes a stream of ASClIl characters and maps them to a stream of tokens, The actual OCaml features which support streams will be discussed in the next section. The produced stream of tokens will be used in the next project (Homework 5) as the input to the parser. In general, the parser reads tokens on demand, as needed to complete the current production. Your lexer should read its input from standard input in Unix. This input will contain a non-empty sequence of lines and your program will produce a list of tokens on standard output. Your program wil be invoked from the command line as follows: $ lexer