How to access first level keys of a 2d array with a foreach loop? [duplicate]
You can access your array keys like so: foreach ($array as $key => $value)
arrays
Variable length arrays (VLA) in C and C++
Yes your reasoning is correct, that is how these different forms of array declarations and definitions are viewed by C and C++. As others already stated, VLA with a veritable variable length (non-const) in global scope is difficult to make sense. What would the evaluation order be, e.g if the the length expression would refer … Read more
Extract certain properties from all objects in array
Use object destructuring to get the properties, and generate a new object using shorthand property names: const dummyArray = [{ “att20”: “att20”, “att30”: “att30”, “att70”: “att70”, “att80”: “att80”}, { “att20”: “att20”, “att30”: “att30”, “att70”: “att70”, “att80”: “att80”}]; const result = dummyArray.map(({ att20, att30, att70, att80 }) => ({ att20, att30, att70, att80 })); console.log(result);
How do you search an array for a substring match?
If you’re able to use Underscore.js in your project, the _.filter() array function makes this a snap: // find all strings in array containing ‘thi’ var matches = _.filter( [ ‘item 1’, ‘thing’, ‘id-3-text’, ‘class’ ], function( s ) { return s.indexOf( ‘thi’ ) !== -1; } ); The iterator function can do whatever you … Read more
How to filter an associative array comparing keys with values in an indexed array?
With array_intersect_key and array_flip: var_dump(array_intersect_key($my_array, array_flip($allowed))); array(1) { [“foo”]=> int(1) }
How to find the size of an array (from a pointer pointing to the first element array)?
No, you can’t. The compiler doesn’t know what the pointer is pointing to. There are tricks, like ending the array with a known out-of-band value and then counting the size up until that value, but that’s not using sizeof(). Another trick is the one mentioned by Zan, which is to stash the size somewhere. For … Read more
Loop over an array in JavaScript
TL;DR Your best bets are usually a for-of loop (ES2015+ only; spec | MDN) – simple and async-friendly for (const element of theArray) { // …use `element`… } forEach (ES5+ only; spec | MDN) (or its relatives some and such) – not async-friendly (but see details) theArray.forEach(element => { // …use `element`… }); a simple … Read more
Why can’t the size of a static array be made variable?
Since the size of the array you declare is not constant, what you have is an Variable Length Array(VLA). VLA are allowed by the c99 standard but there are some limitations associated with it. You cannot have an variable length array with static or extern storage class specifier. You have an VLA with static storage … Read more
Is it possible to initialize std::vector over already allocated memory?
Like this.. Containers in the standard usually take an allocator. Using c++11’s allocator traits, it is very easy to create an allocator as you don’t have to have all the members in the allocator. However if using an older version of C++, you will need to implement each member and do the rebinding as well! … Read more
Correlation of two arrays in C#
You can have the values in separate lists at the same index and use a simple Zip. var fitResult = new FitResult(); var values1 = new List<int>(); var values2 = new List<int>(); var correls = values1.Zip(values2, (v1, v2) => fitResult.CorrelationCoefficient(v1, v2)); A second way is to write your own custom implementation (mine isn’t optimized for … Read more