> It's clear that interfaces are, with concurrency, a distinguishing idea in Go. They are Go's answer to objected-oriented design, in the original, behavior-focused style, despite a continuing push by newcomers to make structs carry that load.

> Making interfaces dynamic, with no need to announce ahead of time which types implement them, bothered some early critics, and still irritates a few, but it's important to the style of programming that Go fostered. Much of the standard library is built upon their foundation, and broader subjects such as testing and managing dependencies rely heavily on their generous, "all are welcome" nature.

> I feel that interfaces are one of the best-designed things in Go.

> Other than a few early conversations about whether data should be included in their definition, they arrived fully formed on literally the first day of discussions.

> And there is a story to tell there.

> On that famous first day in Robert's and my office, we asked the question of what to do about polymorphism. Ken and I knew from C that qsort could serve as a difficult test case, so the three of us started to talk about how our embryonic language could implement a type-safe sort routine.

> Robert and I came up with the same idea pretty much simultaneously: using methods on types to provide the operations that sort needed. That notion quickly grew into the idea that value types had behaviors, defined as methods, and that sets of methods could provide interfaces that functions could operate on. Go's interfaces arose pretty much right away.

> That's something that is not often not acknowledged: Go's sort is implemented as a function that operates on an interface. This is not the style of object-oriented programming most people were familiar with, but it's a very powerful idea.

> That idea was exciting for us, and the possibility that this could become a foundational

> programming construct was intoxicating. When Russ joined, he soon pointed out how I/O would fit beautifully into this idea, and the library took place rapidly, based in large part on the three famous interfaces: empty, Writer, and Reader, holding an average of two thirds of a method each. Those tiny methods are idiomatic to Go, and ubiquitous.

> _THE WAY INTERFACES WORKED became not only a distinguishing feature of Go, they became the way we thought about libraries, and generality, and composition. It was heady stuff.

emphasis at the end there is mine.

how the hell _anyone_ reads that and comes away with the idea that they're claiming they invented the idea of interfaces is beyond me.

my only guess here is that many people are not familiar with the sort problem they're describing.

very famously, C++'s sort is more performant than C's sort because C uses a void pointer and C++ uses templates. The extra type information allows C++ to optimize the sort in a way that C cannot, so while C is generally more performant than C++ in a lot of ways, this is one particular area where C++ shines.

So it's no surprise that Rob Pike, et al, paid close attention to sort as something to improve over C and the way to do that is having more type information available (C++ very clearly has shown this).

> Making interfaces dynamic, with no need to announce ahead of time which types implement them