Ciro Santilli @cirosantilli 40

A 4D gradient with some small special relativity specifics added in (the light of speed and sign change for the time).

Some notable examples:

Example: sqlite/ip.c, adapted from www.sqlite.org/loadext.html, also mentioned explained at: stackoverflow.com/questions/7638238/sqlite-ip-address-storage/76520885#76520885.

Sample usage in the test program: sqlite/test.sh.

Docs: www.sqlite.org/loadext.html

Example where this level is sufficient: nodejs/sequelize/raw/parallel_update_async.js.

A slow development test cycle will kill your software.

New developers won't want to learn your project, because they would rather shoot themselves.

This means that build time, and the time to run tests, must be short.

5 seconds to rebuild is the maximum upper limit.

Of course, at some point software gets large enough that things won't fit anymore in 5 seconds. But then you must have either some kind of build caching, or options to do partial builds/tests that will bring things down to that 5 second mark.

You also have to spend some time profiling execution and build from scratch times.

A slow build from scratch will mean that your continuous integration costs a lot, money that could be invested in a new developer!

It also means that people won't bother to reproduce bugs on given commits, or bisect stuff.

One anecdote comes to mind. Ciro Santilli was trying to debug something, and more experience colleague came over.

To reproduce a problem, ciro was running one command, wait 5 seconds, run a second command, wait 5 seconds, run a third command:

The first thing the colleague said: join those three commands into one:And so, Ciro was enlightened.

If session autosave was finally mainlined, this would be Nirvana.

In Physics, in order to test a theory, you must be able to extract a number from it.

It does not matter how, if it is exact, or numerical, or a message from God: a number has to come out of the formulas in the end, and you have to compare it with the experimental data.

Many theoretical physicists seem to forget this in their lectures, see also: Section "How to teach and learn physics".

A single line in the emission spectrum.

So precise, so discrete, which makes no sense in classical mechanics!

Has been the leading motivation of the development of quantum mechanics, all the way from the:

You just map the value (1, 1) $C_m\times C_n$ to the value 1 of $C_{mn}$, and it works out. E.g. for $C_2\times C_3$, the group generated by of (1, 1) is:

It hasn't achieved anything beyond the Schengen zone.

Related:

Just like for the finite general linear group, the definition of special also works for finite fields, where 1 is the multiplicative identity!

Note that the definition of orthogonal group may not have such a clear finite analogue on the other hand.

Survey by Ciro Santilli: math.stackexchange.com/questions/1985/software-for-drawing-geometry-diagrams/3938216#3938216

Many plotting software can be used to create mathematics illustrations. They just tend to have more data-oriented rather than explanatory-oriented output.