oh silly me. I found the racket guide i was using before at http://www.ccs.neu.edu/home/matthias/HtDP2e/part_prologue.html The other problem still stands though,
On Sun, Dec 9, 2012 at 4:40 PM, Geoffrey Boom <[email protected]>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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