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How is this fibonacci-function memoized?
...nacci definition, fib n = fib (n-1) + fib (n-2), the function itself gets called, twice from the top, causing the exponential explosion. But with that trick, we set out a list for the interim results, and go "through the list":
fib n = (xs!!(n-1)) + (xs!!(n-2)) where xs = 0:1:map fib [2..]
The tr...
MongoDB数据导出导入工具：mongoexport,mongoimport - 大数据 & AI - 清泛...
...ta to CSV, TSV or JSON files.
options:
--help produce help message
-v [ --verbose ] be more verbose (include multiple times for more
verbosity e.g. -vvvvv)
--version print the program's version and exit
-h [ --ho...
How to overcome TypeError: unhashable type: 'list'
...used to compare dictionary keys during a dictionary lookup quickly.
Internally, hash() method calls __hash__() method of an object which are set by default for any object.
Converting a nested list to a set
>>> a = [1,2,3,4,[5,6,7],8,9]
>>> set(a)
Traceback (most recent call last...
What are paramorphisms?
...foldr c n xs)
para c n [] = n
foldr c n [] = n
Some people call paramorphisms "primitive recursion" by contrast with catamorphisms (foldr) being "iteration".
Where foldr's two parameters are given a recursively computed value for each recursive subobject of the input data (here, that...
Get Folder Size from Windows Command Line
...shell -noprofile -command "ls -r|measure -sum Length"
1 I do have a partially-finished bignum library in batch files somewhere which at least gets arbitrary-precision integer addition right. I should really release it, I guess :-)
...
Inherit docstrings in Python class inheritance
...
You're not the only one! There was a discussion on comp.lang.python about this a while ago, and a recipe was created. Check it out here.
"""
doc_inherit decorator
Usage:
class Foo(object):
def foo(self):
"Frobber...
Calling shell functions with xargs
I am trying to use xargs to call a more complex function in parallel.
5 Answers
5
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What's the equivalent of Java's Thread.sleep() in Objective-C/Cocoa?
... Thnx!<br> for future reference, the definition is actually +[NSThread sleepForTimeInterval:] (so, used like [NSThread sleepForTimeInterval:0.1]).
– TinkerTank
Dec 7 '10 at 18:00
...
Select random lines from a file
... @MonaJalal nope just faster, since it doesn't have to compare lines at all.
– rogerdpack
May 15 '17 at 17:20
Does ...
How to open every file in a folder?
...
Os
You can list all files in the current directory using os.listdir:
import os
for filename in os.listdir(os.getcwd()):
with open(os.path.join(os.cwd(), filename), 'r') as f: # open in readonly mode
# do your stuff
Glob
Or you c...