Thank you for these comments. Made me realize that I do not fully
understand my code, and need to think about it a bit more.
I totally understand the huge side effects, and it is true that it would
be dangerous if the function was to actually be used. I would like to
find a fully functional version, using slices then. I propose this :
def linear_merge(list1, list2):
if list1==[]: return list2
elif list2==[]: return list1
elif list1[-1]>list2[-1]:
return linear_merge(list1[:-1],list2)+[list1[-1]]
else:
return linear_merge(list1,list2[:-1])+[list2[-1]]
Or alternatively:
elif list1[-1]>list2[-1]:
b=linear_merge(list1[:-1],list2)
b.append(list1[-1])
return b
Both work but I am not satisfied. Is there not a method that could do
the job of '+' operator (namely concatenate in a copy)?
As for my first code :
def linear_merge1(list1, list2):
if list1==[]: return list2
elif list2==[]: return list1
elif list1[-1]>list2[-1]:
a=list1.pop()
linear_merge(list1,list2).append(a)
return linear_merge(list1,list2)
else:
a=list2.pop()
linear_merge(list1,list2).append(a)
return linear_merge(list1,list2)
I don't get why it works to be fair. It feels like return
linear_merge(list1,list2) does not call the function again. If return
linear_merge(list1,list2) actually returned linear_merged of the lists,
with one of them missing an element, I don't see where this element is
actually added.
I know find it very weird. I would appreciate if you had an explanation
(and if you understood my point)
Thank you for your help,
Gaston
On 03/03/2016 10:29 PM, Danny Yoo wrote:
Some code comments: The solution you have depends very much on
mutation and side effects: I recommend you try to stay as functional
as you can in this situation.
By mixing mutation into the solution, there are certain things that
the program is doing that isn't part of the traditional behavior of a
merge sort.
For example, it is actively mutating the input lists. That's both
surprising and error prone.
Also, the purpose for the second internal calls to the merge sort in
your current solution have nothing to do with merging, but rather to
pick which nonempty list to return as the result. A reader of the
code who doesn't look at this code *very* carefully would wonder why
the function wasn't infinite-looping. It's a bit too clever for its
own good.
Hope that makes sense!
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