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Difference between reduce and foldLeft/fold in functional programming (particularly Scala and Scala

Why do Scala and frameworks like Spark and Scalding have both reduce and foldLeft ? So then what's the difference between reduce and fold ? ...
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Numpy array dimensions

I'm currently trying to learn Numpy and Python. Given the following array: 8 Answers 8...
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How to use concerns in Rails 4

...4 project generator now creates the directory "concerns" under controllers and models. I have found some explanations about how to use routing concerns, but nothing about controllers or models. ...
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What does “@@ -1 +1 @@” mean in Git's diff output?

...:30:39.942229878 -0800 to indicate the date, time with fractional seconds, and time zone. The fractional seconds are omitted on hosts that do not support fractional time stamps. You can change the header's content with the --label=label option; see See Alternate Names. Next come one or mor...
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Python's json module, converts int dictionary keys to strings

...strings; Python supports distinct keys differing only in type. In Python (and apparently in Lua) the keys to a mapping (dictionary or table, respectively) are object references. In Python they must be immutable types, or they must be objects which implement a __hash__ method. (The Lua docs sugges...
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How do I recover/resynchronise after someone pushes a rebase or a reset to a published branch?

...he bookmark of course, if you look up the pre-rebase origin/foo commit ID, and use that. This is also how you deal with the situation where you forgot to make a bookmark before fetching. Nothing is lost – you just need to check the reflog for the remote branch: git reflog show origin/foo | awk '...
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How to add leading zeros?

...s of 10 width 8 too. anim <- 25499:25504 x <- 10 ^ (0:5) paste (and it's variant paste0) are often the first string manipulation functions that you come across. They aren't really designed for manipulating numbers, but they can be used for that. In the simple case where we always have t...
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How do I measure time elapsed in Java? [duplicate]

...answers posted so far are quite right. If you are measuring elapsed time, and you want it to be correct, you must use System.nanoTime(). You cannot use System.currentTimeMillis(), unless you don't mind your result being wrong. The purpose of nanoTime is to measure elapsed time, and the purpose of...
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How to convert an int to string in C?

... EDIT: As pointed out in the comment, itoa() is not a standard, so better use sprintf() approach suggested in the rivaling answer! You can use itoa() function to convert your integer value to a string. Here is an example: int num = 321; char snum[5]; // convert 123 to string...
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Fastest way to list all primes below N

...t William Hanks for primesfrom2to, primesfrom3to, rwh_primes, rwh_primes1, and rwh_primes2. Of the plain Python methods tested, with psyco, for n=1000000, rwh_primes1 was the fastest tested. +---------------------+-------+ | Method | ms | +---------------------+-------+ | rwh_prime...