[wangchow]

I think it's more about the underlying machine as opposed to a particular language implemented on top of Von Neumann architecture. For instance, we are constrained by the underlying machine regardless of which higher-level language we use, functional or otherwise.

I started reading this book on functional languages and lambda calculus. It has some interesting notes on how to build language syntax on top of a purely-functional machine architecture (at least conceptually). Pretty interesting stuff:

[An Introduction to Functional Programming Through Lambda Calculus](http://store.doverpublications.com/0486478831.html)

[gshubert17]

Julian Bigelow, chief engineer of the Institute for Advanced Studies computer project (Von Neumann's first actual computer), stayed at the IAS after Von Neumann left for the AEC (and died in 1957) and believed the architecture was the limiting factor.

"The modern high speed computer, impressive as its performance is from the point of view of absolute accomplishment, is from the point of view of getting the available logical equipment adequately engaged in the computation, very inefficient indeed." The individual components, despite being capable of operating continuously at high speed, "are interconnected in such a way that on the average almost all of them are waiting for one (or a very few of their number) to act. The average duty cycle of each cell is scandalously low."

Julian Bigelow, quoted in George Dyson, "Turing's Cathedral", pg. 276

[adwn]

That's because they're universal, programmable computers. If you have a very specific, fixed task (e.g., matrix*vector multiplication), then you can build a chip in which a much higher number of transistors does useful work in each cycle. You won't be able to browse the web, watch a video, do your taxes, or program other computers with it, though.

[DigitalJack]

I am naive when it comes to computation science, but doesn't the turing completeness of someting essentially mean you are not constrained? Perhaps constrained in efficiency, but not outcome.

[adwn]

As soon as you target an actual user doing stuff on an actual computer, there will always be constraints due to efficiency and performance. You might not run into them, because your program is sufficiently small and the hardware sufficiently fast, but they're always there.

[jononor]

Constraints which are not hit are not very constraining...