filter should be an iterator or generator

In the current implementation filter is a function returning a list, this is not the intended behavior, for example:

filter(42, (1,2))

shouldn't give an error, the error should be generated when we iterate the result, for example:

list(filter(42, (1,2)))

should give a TypeError exception.

In fact, this example is taken from the python-reference/builtin/filter.py test, which is passed only do to this "patch" which hides the problem:

  ;; very hacky solution for assertRaises: it needs laziness built into it, so instead
  ;; of defining it as a function, we'll special case it as a macro.
  [PyApp (fun args)
         (cond
           #|[(and (PyId? fun) (symbol=? (PyId-x fun) '___assertRaises))
            (local [(define f (rec-desugar (second args) global? env (none)))
                    (define-values (as as-env)
                      (map-desugar (rest (rest args)) global? (DResult-env f) (none)))
                    (define exns (rec-desugar (first args) global? as-env (none)))
                    (define pass (rec-desugar (PyPass) global? (DResult-env exns) (none)))]
              (DResult
               (CApp
                (CFunc empty (none)
                       (CTryExceptElseFinally
                        (CApp (DResult-expr f) as (none))
                        (list
                         (CExcept (list (DResult-expr exns)) (none) (DResult-expr pass))
                         (CExcept empty (none) (DResult-expr pass)))
                        (CApp (CId 'print (GlobalId))
                              (list (make-builtin-str "Assert failure!"))
                              (none))
                        (DResult-expr pass))
                       (none))
                empty
                (none))
               (DResult-env pass)))]|#

brownplt / lambda-py

filter should be an iterator or generator #37