From: chrysn <chrysn@web>
Date: Fri, 16 Mar 2012 01:36:36 +0000 (-0400)
Subject: the algorithms required for map plugin sorting
X-Git-Url: http://git.tremily.us/?a=commitdiff_plain;h=128234cde1ed0504d6beb0b2d10544feb2d77809;p=ikiwiki.git

the algorithms required for map plugin sorting
---

diff --git a/doc/todo/sort_parameter_for_map_plugin_and_directive/python_algorithms.py b/doc/todo/sort_parameter_for_map_plugin_and_directive/python_algorithms.py
new file mode 100644
index 000000000..ccee8185d
--- /dev/null
+++ b/doc/todo/sort_parameter_for_map_plugin_and_directive/python_algorithms.py
@@ -0,0 +1,81 @@
+testdata = "c/3 a b d b/1 c/1 c/2/x c/2 c".split(" ")
+
+def strategy_byearlychild(sequence):
+    """Sort by earliest child
+
+    When this strategy is used, a parent is displayed with all its children as
+    soon as the first child is supposed to be shown.
+
+    >>> strategy_byearlychild(testdata)
+    ['c', 'c/3', 'c/1', 'c/2', 'c/2/x', 'a', 'b', 'b/1', 'd']
+    """
+
+    # first step: pull parents to top
+    def firstchildindex(item):
+        childindices = [i for (i,text) in enumerate(sequence) if text.startswith(item + "/")]
+        # distinction required as min(foo, *[]) tries to iterate over foo
+        if childindices:
+            return min(sequence.index(item), *childindices)
+        else:
+            return sequence.index(item)
+    sequence = sorted(sequence, key=firstchildindex)
+
+    # second step: pull other children to the start too
+    return strategy_byparents(sequence)
+
+def strategy_byparents(sequence):
+    """Sort by parents only
+
+    With this strategy, children are sorted *under* their parents regardless of
+    their own position, and the parents' positions are determined only by
+    comparing the parents themselves.
+
+    >>> strategy_byparents(testdata)
+    ['a', 'b', 'b/1', 'd', 'c', 'c/3', 'c/1', 'c/2', 'c/2/x']
+    """
+
+    def partindices(item):
+        return tuple(sequence.index(item.rsplit('/', i)[0]) for i in range(item.count('/'), -1, -1))
+
+    return sorted(sequence, key=partindices)
+
+def strategy_forcedsequence(sequence):
+    """Forced Sequence Mode
+
+    Using this strategy, all entries will be shown in the sequence; this can
+    cause parents to show up multiple times.
+
+    The only reason why this is not the identical function is that parents that
+    are sorted between their children are bubbled up to the top of their
+    contiguous children to avoid being repeated in the output.
+
+    >>> strategy_forcedsequence(testdata)
+    ['c/3', 'a', 'b', 'd', 'b/1', 'c', 'c/1', 'c/2', 'c/2/x']
+    """
+
+    # this is a classical bubblesort. other algorithms wouldn't work because
+    # they'd compare non-adjacent entries and move the parents before remote
+    # children. python's timsort seems to work too...
+
+    for i in range(len(sequence), 1, -1):
+        for j in range(1, i):
+            if sequence[j-1].startswith(sequence[j] + '/'):
+                sequence[j-1:j+1] = [sequence[j], sequence[j-1]]
+
+    return sequence
+
+def strategy_forcedsequence_timsort(sequence):
+    sequence.sort(lambda x,y: -1 if y.startswith(x) else 1)
+    return sequence
+
+if __name__ == "__main__":
+    import doctest
+    doctest.testmod()
+
+    import itertools
+
+    for perm in itertools.permutations(testdata):
+        if strategy_forcedsequence(testdata[:]) != strategy_forcedsequence_timsort(testdata[:]):
+            print "difference for testdata", testdata
+            print "normal", strategy_forcedsequence(testdata[:])
+            print "timsort", strategy_forcedsequence_timsort(testdata[:])