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[SVN r26341]

doc/src/refmanual/Algorithms-Iteration.rst

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+Iteration algorithms are the basic building blocks behind many of the 
+MPL's algorithms, and are usually the first place to look at when 
+starting to build a new one. Abstracting away the details of sequence 
+iteration and employing various optimizations such as recursion 
+unrolling, they provide significant advantages over a hand-coded 
+approach.
+
+..  Of all of iteration algorithms, ``iter_fold_if`` is the 
+    most complex and at the same time the most fundamental. The rest of 
+    the algorithms from the category |--| ``iter_fold``, ``reverse_iter_fold``,
+    ``fold``, and ``reverse_fold`` |--| simply provide a more high-level 
+    (and more restricted) interface to the core ``iter_fold_if`` 
+    functionality [#performace]_.
+
+    .. [#performace] That's not to say that they are *implemented*
+    through ``iter_fold_if`` |--| they are often not, in particular 
+    because the restricted functionality allows for more 
+    optimizations.