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copied!<p>To quote the <a href="http://en.wikipedia.org/wiki/Delimited_continuation" rel="nofollow">wikipedia</a>:</p> <blockquote> <p>a delimited continuation, composable continuation or partial continuation, is a "slice" of a continuation frame that has been reified into a function. </p> </blockquote> <p>Scala syntax for this is:</p> <pre><code>// Assuming g: X => anything reset { A g(shift { (f: (X) => Y) => /* code using function f */ }) B } </code></pre> <p>A <em>continuation frame</em> above is everything that would be executed <em>after</em> the <code>shift</code> up until the end of the block delimited by <code>reset</code>. That includes calling the function <code>g</code>, since it would only be called <em>after</em> evaluating <code>shift</code>, plus all the code in <code>B</code>.</p> <p>The function <code>g</code> is not required -- one could be calling a method instead, or completely ignore the result of <code>shift</code>. I show it just to make clear that the <code>shift</code> call returns a value that can be used.</p> <p>In other words, that continuation frame becomes the following function:</p> <pre><code>// Assuming g: X => anything def f: (X) => Y = { x => g(x) B } </code></pre> <p>And the whole reset body becomes this:</p> <pre><code>// Assuming g: X => anything A def f: (X) => Y = { x => g(x) B } /* code using function f */ </code></pre> <p>Note that the last statement in <code>B</code> must have type <code>Y</code>. The result of the computation is the result of the contents of the <code>shift</code> block, as would happen with that translation above.</p> <p>If you want more precision, <a href="http://lamp.epfl.ch/~rompf/continuations-icfp09.pdf" rel="nofollow">check the paper</a> that describes delimited continuations in Scala. The exact types can be found on the <a href="http://www.scala-lang.org/archives/downloads/distrib/files/nightly/docs/library/index.html#scala.util.continuations.package" rel="nofollow">API documentation</a>.</p>

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