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What is Weak Head Normal Form?

... further (i.e. it contains no un-evaluated thunks). These expressions are all in normal form: 42 (2, "hello") \x -> (x + 1) These expressions are not in normal form: 1 + 2 -- we could evaluate this to 3 (\x -> x + 1) 2 -- we could apply the function "he" ++ "llo" ...
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Understand the “Decorator Pattern” with a real world example

... Decorator pattern achieves a single objective of dynamically adding responsibilities to any object. Consider a case of a pizza shop. In the pizza shop they will sell few pizza varieties and they will also provide toppings in the menu. Now imagine a situation wherein if the piz...
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What are file descriptors, explained in simple terms?

...you open a network socket, it is also represented by an integer and it is called Socket Descriptor. I hope you understand. share | improve this answer | follow ...
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AngularJS Multiple ng-app within a page

... So basically as mentioned by Cherniv we need to bootstrap the modules to have multiple ng-app within the same page. Many thanks for all the inputs. var shoppingCartModule = angular.module("shoppingCart", []) shoppingCartModule...
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How can I merge properties of two JavaScript objects dynamically?

...Later properties overwrite earlier properties with the same name. */ const allRules = {...obj1, ...obj2, ...obj3}; Here is also the MDN documentation for this syntax. If you're using babel you'll need the babel-plugin-transform-object-rest-spread plugin for it to work. ECMAScript 2015 (ES6) Stand...
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Is it possible to have multiple statements in a python lambda expression?

...Q. Can you put multiple statements in a lambda? A. No. But you don't actually need to use a lambda. You can put the statements in a def instead. i.e.: def second_lowest(l): l.sort() return l[1] map(second_lowest, lst) Q. Can you get the second lowest item from a lambda by sorting the ...
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Using Default Arguments in a Function

...= "some other value"; } code here! } This way, you can make a call like foo('blah', null, 'non-default y value'); and have it work as you want, where the second parameter $x still gets its default value. With this method, passing a null value means you want the default value for one par...
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Unresolved specs during Gem::Specification.reset:

...t turned out to be a missing line in the gemspec file: $:.push File.expand_path("../lib", __FILE__) This line is normally at the top of the file (in many of the gems I have recently been working in) and I had commented it out to see why. ...
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How to write :hover condition for a:before and a:after?

... This depends on what you're actually trying to do. If you simply wish to apply styles to a :before pseudo-element when the a element matches a pseudo-class, you need to write a:hover:before or a:visited:before instead. Notice the pseudo-element comes after ...
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What is a “callback” in C and how are they implemented?

...y're implemented using function pointers. Here's an example: void populate_array(int *array, size_t arraySize, int (*getNextValue)(void)) { for (size_t i=0; i<arraySize; i++) array[i] = getNextValue(); } int getNextRandomValue(void) { return rand(); } int main(void) { int m...