Lambda_lib.Interprettype 'a eval_result = ('a, error) Stdlib.resultval ok : 'a -> 'a eval_resultval error : error -> 'a eval_resultval (let*) : 'a eval_result -> ('a -> 'b eval_result) -> 'b eval_resultval initial_env : envval string_of_value : value -> stringval string_of_error : error -> string