In calculus, the product rule is a formula used to find the derivatives of products of two or more functions. It may be stated thus: :(f\cdot g)'=f'\cdot g+f\cdot g' \,\! or in the Leibniz notation thus: :\dfrac{d}{dx}(u\cdot v)=u\cdot \dfrac{dv}{dx}+v\cdot \dfrac{du}{dx}. In the notation of differentials this can be written as follows: : d(uv)=u\,dv+v\,du. The derivative of the product of three functions is: :\dfrac{d}{dx}(u\cdot v \cdot w)=\dfrac{du}{dx} \cdot v \cdot w + u \cdot \dfrac{dv}{dx} \cdot w + u\cdot v\cdot \dfrac{dw}{dx}. Discovery Discovery of this rule is credit...

The brainfuck programming language is an esoteric programming language noted for its extreme minimalism. It is a Turing tarpit, designed to challenge and amuse programmers, and was not made to be suitable for practical use. It was created in 1993 by Urban Müller. The name of the language is generally not capitalized except at the start of a sentence, although it is a proper noun. Language design Urban Müller created brainfuck in 1993 with the intention of designing a language which could be implemented with the smallest possible compiler, inspired by the 1024-byte compiler for the FA...