[racket] printf: this function is not defined

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#lang racket

declared at the top of your source code and have chosen the appropriate
radio button from the Choose Language... menu. It sounds like you're stuck
in one of the teaching languages.

On Sun, Dec 9, 2012 at 4:40 PM, Geoffrey Boom <geoff.the.boom at gmail.com>wrote:

> I'm having trouble with the racket guide. First of all, I havent used it
> in a little while, so I was surprised when I looked for the guide, and I
> think it's new, and I can't find the old one.
>
> That's not my main problem, though. I'm at the section that goes like this:
>
> A function definition can include multiple expressions for the function’s
> body. In that case, only the value of the last expression is returned when
> the function is called. The other expressions are evaluated only for some
> side-effect, such as printing.
>
> Examples:
> (define (bake flavor)
>   (printf "pre-heating oven...\n")
>   (string-append flavor " pie"))
> > (bake "apple")
> pre-heating oven...
> "apple pie"
>
> Here's everything I've entered so far.
>
> (define (extract str)
>   (substring str 4 7))
>
>
> (extract "the boy out of the country")
> (extract "the country out of the boy")
>
> (define (bake flavor)
>   (printf "preheating oven..\n")
>   (string-append flavor " pie"))
>
> (bake "apple")
>
> and I get the error message
>
> define: expected only one expression for the function body, but found 1
> extra part
>
> So I try taking out (string-append flavor " pie") and get a second error
> message
>
> printf: this function is not defined
>
>
> I understand that define expects two sections after it (the name it
> defines and the definition it enters when triggered) so in this case the
> "string-append" would be the one extra. But I dont understand why the
> "printf" thing doesn't work. Nor do I know what the "printf" function does,
> as it's not explained in the guide.
>
> I tried entering *just* what the guide said to enter, as in copy pasting
> it in, but still get the same problems.
>
> Any help? :(
>
>
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>
>
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