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What's the difference between passing by reference vs. passing by value?
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First and foremost, the "pass by value vs. pass by reference" distinction as defined in the CS theory is now obsolete because the technique originally defined as "pass by reference" has since fallen out of favor and is seldom used now.1
Newer languages2 ...
Is Ruby pass by reference or by value?
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In traditional terminology, Ruby is strictly pass-by-value. But that's not really what you're asking here.
Ruby doesn't have any concept of a pure, non-reference value, so you certainly can't pass one to a method. Variables are always references to objec...
Is it better in C++ to pass by value or pass by constant reference?
Is it better in C++ to pass by value or pass by constant reference?
10 Answers
10
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Using group by on multiple columns
I understand the point of GROUP BY x .
2 Answers
2
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Are arrays passed by value or passed by reference in Java? [duplicate]
...itive type in Java, but they are not objects either , so are they passed by value or by reference? Does it depend on what the array contains, for example references or a primitive type?
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How to sort an array in descending order in Ruby
... on the various suggested answers. Here's what I found out:
#!/usr/bin/ruby
require 'benchmark'
ary = []
1000.times {
ary << {:bar => rand(1000)}
}
n = 500
Benchmark.bm(20) do |x|
x.report("sort") { n.times { ary.sort{ |a,b| b[:bar] <=> a[:bar] } } }
x.repor...
MySQL “Group By” and “Order By”
...o be able to select a bunch of rows from a table of e-mails and group them by the from sender. My query looks like this:
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What's faster, SELECT DISTINCT or GROUP BY in MySQL?
...e the same, a query optimizer would have to catch the fact that your GROUP BY is not taking advantage of any group members, just their keys. DISTINCT makes this explicit, so you can get away with a slightly dumber optimizer.
When in doubt, test!
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Call by name vs call by value in Scala, clarification needed
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The example you have given only uses call-by-value, so I will give a new, simpler, example that shows the difference.
First, let's assume we have a function with a side-effect. This function prints something out and then returns an Int.
def something() = {
print...
PostgreSQL DISTINCT ON with different ORDER BY
... [...] Note that the "first row" of each set is unpredictable unless ORDER BY is used to ensure that the desired row appears first. [...] The DISTINCT ON expression(s) must match the leftmost ORDER BY expression(s).
Official documentation
So you'll have to add the address_id to the order by.
Alt...