Looks like an interesting language for scientific/engineering applications. It's designed to be heavily parallel (for-loops are parallel by default), it uses math-type notation (although I'm dubious about the whole "2 x" being the same as "2*x" thing).

Over at se-radio in Nov. 2006, they did an interesting interview with Guy Steele about Fortress: http://www.se-radio.net/podcast/2006-11/episode-36-interview...

although I'm dubious about the whole "2 x" being the same as "2.x" thing (the * isn't printing. meh)

It might not make much sense from a programming perspective, but it's very natural for a mathematician. The same way that mathematicians are happy with one-letter variable names, they're happy with juxtaposition as their one operator notation. They just redefine everything whenever they start a new problem.

If you think about it, matrix multiplication is a totally different operation from multiplication in the reals. We just happen to use the same notation for it because it follows some of the same rules (associativity, distributivity) that we're in the habit of using to manipulate equations.

This can get pretty extreme. There's a branch of math called functional analysis, which identifies functions with infinite-dimensional vectors, and then does calculus on those "vectors" like they were points in any other space. In their notation,

v = Tu

is like matrix multiplication

y = Ax

except that u and v are functions, and T is some kind of integral.

I think this is one reason the Lisp crowd gets cranky about the parenthesis thing -- the infix operators we all know and love are a lot less well-defined than we think they are.

Regex have a juxtapositional operator (for concatenation). Any others in mainstream languages?

Juxtaposition in ML is function application: f x y = f(x,y)

Although you're free to discount ML and its ilk (OCaml, Haskell) as non-mainstream.

This isn't quite the same juxtaposition as math, though. In math you just put single letters next to each other and it's multiplication. But in any programming language enforcing single-letter names would be crazy....

Juxtaposition Mathematica works pretty much the same way as in Fortress. When you multiply a number with a variable you don't even need the whitespace (the pretty printer will however make a "half-space" to ease reading).

String interpolation in shell, Python etc; and format specification in C-style printf.

It's like APL all over again.

Is it just me or does this look really similar to Scala.