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Random record in ActiveRecord
...can (or table scan, in case clustered index is used like InnoDB). In other words, it's O(N) operation but "WHERE id >= #{rand_id} ORDER BY id ASC LIMIT 1" is O(log N), which is much faster.
– kenn
May 6 '11 at 1:02
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Why do python lists have pop() but not push()
...rticular
semantics, write a little class that
uses a lists
In other words, for stacks implemented directly as Python lists, which already supports fast append(), and del list[-1], it makes sense that list.pop() work by default on the last element. Even if other languages do it differently.
I...
Is there a way to change the environment variables of another process in Unix?
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@kilaka: The key word is the second one — No. The rest of the answer is saying that if you have root privileges or are running a debugger, then maybe you can do it, but for all practical purposes, the answer is No.
– ...
I do not want to inherit the child opacity from the parent in CSS
...tually inherited in CSS. It's a post-rendering group transform. In other words, if a <div> has opacity set you render the div and all its kids into a temporary buffer, and then composite that whole buffer into the page with the given opacity setting.
What exactly you want to do here depends...
Functions that return a function
...ts, like any other object. If you find that not helpful, just replace the word "object" with "thing". You can return any object from a function. You can return a true/false value. An integer (1,2,3,4...). You can return a string. You can return a complex object with multiple properties. And y...
Recursion or Iteration?
...ursive function and the benefits of using tail-end recursion. His closing words really summed up some of my key points I think:
"recursive programming gives the programmer a better way of organizing
code in a way that is both maintainable and logically consistent."
https://developer.ibm...
Python append() vs. + operator on lists, why do these give different results?
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if an element is single string, e.g. s = 'word', l = ['this', 'is']. Then l.append(s) and l+s should be the same. Am I correct?
– user3512680
Feb 2 at 22:13
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Update R using RStudio
...swer that you must close and reopen RStudio (or restart RStudio, whichever wording you prefer). The "Then you change the path in your Rstudio option :Tools -> options -> General" did not work for me. However, restarting R did, so it would be good to update your answer to include this info.
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How to loop through files matching wildcard in batch file
...ve the %%I variable it's easy to perform a command on it (just replace the word echo with your program)
In addition, substitution of FOR variable references has been enhanced
You can now use the following optional syntax:
%~I - expands %I removing any surrounding quotes (")
%~fI - e...
What is the difference between `let` and `var` in swift?
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The let keyword defines a constant:
let theAnswer = 42
The theAnswer cannot be changed afterwards. This is why anything weak can't be written using let. They need to change during runtime and you must be using var instead.
The var ...