TLA+ is based on the idea that the best way to describe things formally is with simple mathematics, and that a specification language should contain as little as possible beyond what is needed to write simple mathematics precisely. TLA+ is especially well suited for writing high-level specifications of concurrent and distributed systems.
PlusCal is an algorithm language that, at first glance, looks like a typical tiny toy programming language. However, a PlusCal expression can be any TLA+ expression, which means anything that can be expressed with mathematics. This makes PlusCal much more expressive than any (real or toy) programming language. A PlusCal algorithm is translated into a TLA+ specification, to which the TLA+ tools can be applied.
America’s new tribalism can be seen most distinctly in its politics. Nowadays the members of one tribe (calling themselves liberals, progressives, and Democrats) hold sharply different views and values than the members of the other (conservatives, Tea Partiers, and Republicans).
Each tribe has contrasting ideas about rights and freedoms (for liberals, reproductive rights and equal marriage rights; for conservatives, the right to own a gun and do what you want with your property).
Each has its own totems (social insurance versus smaller government) and taboos (cutting entitlements or raising taxes). Each, its own demons (the Tea Party and Ted Cruz; the Affordable Care Act and Barack Obama); its own version of truth (one believes in climate change and evolution; the other doesn’t); and its own media that confirm its beliefs.
The tribes even look different. One is becoming blacker, browner, and more feminine. The other, whiter and more male. (Only 2 percent of Mitt Romney’s voters were African-American, for example.)