Can't understand example using continuations

Posted by Matt Fenwick on Programmers See other posts from Programmers or by Matt Fenwick
Published on 2012-07-03T13:50:47Z Indexed on 2012/07/03 15:24 UTC
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Scheme

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continuation

I'm reading the r6rs Scheme report and am confused by the explanation of continuations (I find it to be too dense and lacking of examples for a beginner).

What is this code doing and how does it evaluate to 4? Why does call/cc want an argument that's a function of one argument? How is call/cc's argument used?

(+ 1 (call-with-current-continuation
       (lambda (escape)
         (+ 2 (escape 3)))))
          =? 4

This example is from section 1.11 - Continuations.

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