[Python-bugs-list] [ python-Bugs-457399 ] bisect module broken in 2.1.1 ?

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Bugs item #457399, was opened at 2001-08-31 13:40
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Category: Python Library
>Group: Not a Bug
>Status: Closed
>Resolution: Invalid
Priority: 5
Submitted By: Daniel Mahler (dmahler)
>Assigned to: Tim Peters (tim_one)
Summary: bisect module broken in 2.1.1 ?

Initial Comment:
given the function:

def findClause(C, SS):
    for j in range(1,len(SS)):
        assert SS[j-1] <= SS[j], (j, SS[j-1], SS[j])
    C2 = map(abs, C)
    i = bisect.bisect_left(C2, SS)
    assert C2 >= SS[i], (i, C, C2, [C3 for C3 in SS if
C3 <= C2], SS[0:4])
    return i

I get:

    i = findClause(C, SS)
  File "/home/mahler/code/scripts/oshl.py", line 248,
in findClause
    assert C2 >= SS[i], (i, C, C2, [C3 for C3 in SS if
C3 <= C2], SS[0:4])
AssertionError: (3, [5, -2, 1], [5, 2, 1], [], [[5, 3,
1], [5, 3, 2], [6, 4, 2], [7, 3, 2]])

As far as I can tell this must be a bug:
the first loop ensures that the list is sorted.
It is the bottom asertion that is throwing the
exception
The values returned with the exception show that we
were
looking for an element smaller than any in the list.
I would therefore expect 0 to be returned,
but I get 3.

Daniel Mahler
mahler@cyc.com

----------------------------------------------------------------------

>Comment By: Tim Peters (tim_one)
Date: 2001-08-31 14:05

Message:
Logged In: YES 
user_id=31435

It looks like you passed arguments to bisect in the wrong 
order.  Try

i = bisect.bisect_left(SS, C2)

instead.  As is, you're looking for the position within 
list [5, 2, 1] to insert element SS (the opposite of what I 
expect you intended), and since any list *happens to* 
compare greater than any integer in 2.1, the list SS 
belongs at position C2[3].

----------------------------------------------------------------------

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