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What's an elegant way to conditionally add a class to an HTML element in a view?

...sses where the boolean value evaluated to true. Sample Usage class_names(foo: true, bar: false, baz: some_truthy_variable) # => "foo baz" Other Use Cases This helper can be used within ERB tags or with Rails helpers such as link_to. <div class="<%= class_string(ok: @success) %>"&gt...
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How to use range-based for() loop with std::map?

... called structured bindings, which allows for the following: std::map< foo, bar > testing = { /*...blah...*/ }; for ( const auto& [ k, v ] : testing ) { std::cout << k << "=" << v << "\n"; } ...
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Rename multiple files by replacing a particular pattern in the filenames using a shell script [dupli

...ho "$f" | sed s/IMG/VACATION/)"; done In this example, I am assuming that all your image files contain the string IMG and you want to replace IMG with VACATION. The shell automatically evaluates *.jpg to all the matching files. The second argument of mv (the new name of the file) is the output of t...
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How to get thread id from a thread pool?

...ncrementing an internal counter: hg.openjdk.java.net/jdk8/jdk8/jdk/file/687fd7c7986d/src/share/… – Burhan Ali Sep 19 '15 at 0:44 7 ...
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List goals/targets in GNU make that contain variables in their definition

...utput from make -pn (i.e. make --print-data-base --dry-run)? It prints out all the variables, rules, implicit rules and which commands will be run in laborious detail. share | improve this answer ...
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Warning on “diff.renamelimit variable” when doing git push

...ld still be partially buffered when we print these warnings (directly to fd 2). The output is messed up like this worktree.c | 138 +- worktree.h warning: inexact rename detection was skipped due to too many files. | 12 ...
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Join strings with a delimiter only if strings are not null or empty

... .filter(Boolean) (which is the same as .filter(x => x)) removes all "falsy" values (nulls, undefineds, empty strings etc). If your definition of "empty" is different, then you'll have to provide it, for example: [...].filter(x => typeof x === 'string' && x.length > 0) wi...
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Define a lambda expression that raises an Exception

...ur goal is to avoid a def, this obviously doesn't cut it. It does, however allow you to conditionally raise exceptions, e.g.: y = lambda x: 2*x if x < 10 else raise_(Exception('foobar')) Alternatively you can raise an exception without defining a named function. All you need is a strong stom...
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How to convert PascalCase to pascal_case?

...esult [$output]\n"; } } function from_camel_case($input) { preg_match_all('!([A-Z][A-Z0-9]*(?=$|[A-Z][a-z0-9])|[A-Za-z][a-z0-9]+)!', $input, $matches); $ret = $matches[0]; foreach ($ret as &$match) { $match = $match == strtoupper($match) ? strtolower($match) : lcfirst($match); } ...
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Set Django IntegerField by choices=… name

... Really like the Encapsulation section on the blog. – Nathan Keller Mar 3 '13 at 21:57 ...