The fact is that E[X^2] is natural way of an important concept. Whereas "\sum \sum (x_i)^2 p(x_i^2)", need mean nothing at all (especially is $p$ is not defined over all the $x_i^2$).
The fact is that E[X^2] is natural way of an important concept. Whereas "\sum \sum (x_i)^2 p(x_i^2)", need mean nothing at all (especially is $p$ is not defined over all the $x_i^2$).
Then how come an unfamiliar piece of source code is easier to follow than a mathematics paper using unfamiliar notation?
You can look up the definition of each function and learn precisely what it does, without ambiguities. You can open up a debugger and trace every step of the algorithm. Source code tends to be formatted to emphasise its division into units that can be analysed separately. Even if the code uses a framework you don't recognise, you can probably understand some of the underlying logic just fine, thanks to a consistent syntax and (often) descriptive function names.
In a mathematical paper, often there's some notation that isn't defined and there isn't even any pointer where to look for definitions. Important objects are given one-letter names. Theorems are often only numbered; good luck remembering what lemma 2.17.3b was about. Proofs are written in prose (instead of something like Leslie Lamport proposed[0]). You have to fill in conceptual gaps and remind yourself of unstated assumptions. Notation and terminology is often ambiguous — what does "exponential time" mean? Is it DTIME(2^(c*n)) or DTIME(2^polynomial(n))? Does "increasing" mean "strictly increasing" or "non-decreasing"? Is zero a natural number? And so on.
A mathematical formalism that could be interpreted in a purely mechanical way would be a huge improvement.
[0] http://research.microsoft.com/en-us/um/people/lamport/pubs/p...
This is clearly subjective. I read lots of mathematics research that I find more accessible than even pretty mundane source code (and yes, I write software for a living and have done so for over ten years).
Look at Homotopy Type Theory:
that is a princial problem with his blog post.
In a way he is also kind of right - although I don't agree with his conclusion. E[X^2] is not the most precise notation. I have occasionally seen notations like E_X[X^2] to avoid confusion and clearly state "the expected value for X^2 with respect to the distribution of X" or something like that. I remember multiple times were imprecise notation has kept me from understanding statistical methods, while I would say that I am reasonably familiar with the field.
Another problem: Different "schools" use different notations, which are then mixed arbitrarily. This is a major problem for example on Wikipedia, where articles use different notation and sometimes switch notations within the article.