CODEWITHSUNDEEP
schemelispracket
Christopher Kelly
Christopher Kelly

Reputation: 117

Racket Scheme - stream-map issue

I am having a problem implementing stream-map for the purpose of removing newlines from a stream of characters.

Below is my current implementation of remove-newlines:

 (define remove-newlines2
  (lambda (str)
    (cond
      ((stream-empty? str) '())
      (else (stream-map (lambda (x)
                          (cond
                            ((equal? x #\newline) (remove x str ))
                            (else '())
                            )) ;procedure
                          str ; stream
  )))))

I've toyed around with different implementations. However, it appears that no matter what I do, Racket only recognizes it as a stream, and does nothing further:

(remove-newlines2 (file->stream "text-source-file"))
#<stream>
>

Is there something simple I'm missing here?

Upvotes: 2

Views: 275

Answers (1)

&#211;scar L&#243;pez
&#211;scar L&#243;pez

Reputation: 235984

It's the expected behavior, because stream-map returns a stream as its output. To get its contents you have to evaluate or force the result, for instance using stream->list on the stream:

(stream->list (remove-newlines2 (file->stream "text-source-file")))

Upvotes: 1

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