hello — first Rail program

The smallest meaningful Rail program: define two functions before main, call them, print the results. main is the entry point and must return an int (0 = success).

\1 (examples/hello.rail):

-- hello.rail — first Rail program (compiles natively)

double x = x * 2
factorial n = if n <= 1 then 1 else n * factorial (n - 1)

main =
  let _ = print "hello, rail"
  let _ = print (factorial 10)
  let _ = print (double 21)
  0

\1

./rail_native run examples/hello.rail

\1

Compiling examples/hello.rail (244 chars)...
  as: OK
  ld: OK
hello, rail
3628800
42

The first three lines come from the compiler driver (as = assembler, ld = linker). Everything below is the program output: the greeting, 10! = 3628800, and 21 * 2 = 42.