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Why does scanf() need “%lf” for doubles, when printf() is okay with just “%f”?
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Since С99 the matching between format specifiers and floating-point argument types in C is consistent between printf and scanf. It is
%f for float
%lf for double
%Lf for long double
It just so happens that when arguments of type float are passed as variadic parameters,...
Any implementation of Ordered Set in Java?
...Objective-C there is a collection called NSOrderedSet that acts as Set and its items can be accessed as an Array 's ones.
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When to use references vs. pointers
I understand the syntax and general semantics of pointers versus references, but how should I decide when it is more-or-less appropriate to use references or pointers in an API?
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Using union and order by clause in mysql
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select 3 as Rank, id, add_date from Table where distance between 5 and 15
) a
order by rank, id, add_date desc
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Ruby: kind_of? vs. instance_of? vs. is_a?
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kind_of? and is_a? are synonymous.
instance_of? is different from the other two in that it only returns true if the object is an instance of that exact class, not a subclass.
Example:
"hello".is_a? Object and "hello".kind_of? Obje...
What is a lambda (function)?
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Lambda comes from the Lambda Calculus and refers to anonymous functions in programming.
Why is this cool? It allows you to write quick throw away functions without naming them. It also provides a nice way to write closures. With that power you can do things like...
JPA EntityManager: Why use persist() over merge()?
EntityManager.merge() can insert new objects and update existing ones.
15 Answers
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How to implement the activity stream in a social network
I'm developing my own social network, and I haven't found on the web examples of implementation the stream of users' actions... For example, how to filter actions for each users? How to store the action events? Which data model and object model can I use for the actions stream and for the actions it...
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...
ASP.NET MVC - TempData - Good or bad practice
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I kind of think of temp data as being a fire-and-forget mechanism for notifying the user. Its great to give them a reminder of something they recently did, but I'd also be hesitant to make it a required step in some user process. The reason being if they refresh the p...