Yield to the Block (in Ruby)
Related link: http://www.rubyist.net/~matz/slides/oscon2005/
In the words of Danny O'Brien, Ruby moved from being ignored to winning in about three weeks. How did it do that? In part, Matz made a powerful concept ubiquitous and simple. Plenty of languages have useful higher-order functions, but few allow you to pass them to just about every built-in function or method. By shaving off the rough corners of syntax and relentlessly pushing for consistency, Ruby makes blocks so easy to use you don't have to think of closures, coroutines, and other complicated things. They're just idioms. Matz' OSCON 2005 presentation explains.
What will be the good next example of generalization and synthesis in a programming language?
More about this talk
I wrote some detailed notes here: http://tech.rufy.com/entry/78