I do not know much about python, but I am surprised the following code works:
import sys
prev = [sys.maxint]*(5)
j = 0
print prev[j]
print prev[j-1]
In general I thought second print statement should give me an error. Why does this work?
I need to convert some python code into C++, and in C++ this will not work.
mylist[-1] returns the last item of mylist, mylist[-2] the second-to-last item etc.
This is by design. Read the tutorial.
That's because j - 1 evaluates to -1, which when used as index of python list, means last element.
The index of an array l can be an integer in the range [-len(l), len(l)-1] (note: inclusive on both ends). You are familiar with the indices in the range [0, len(l)-1]. The indices in the range [-len(l),-1] are as follows: take i in that range, then l[i] == l[len(l) + i]. Essentially, negative numbers count backwards from the end of the array.
Thus, prev[j-1] = prev[-1] = prev[len(prev) + -1] = prev[5 - 1] = prev[4], or the last element in the array.
