Ticket 162 - expressions computing return values a la Rust/R

[lutzhamel]

The fixes introduced here allow programs such as

let x = (lambda with i do i+1) 1.
assert(x is 2).

and

load system io.

function f1 with () do
   3+3.
   io @println "hello".
   5.
end

function f2 with () do
   3+3.
   io @println "hello".
end

assert(f1() is 5).
assert(f2() is none).

where the last expression evaluated in a function body computes the return value of that function.

[olwmc]

where the last expression evaluated in a function body computes the return value of that function.. I didn't think of it this way but that's very interesting! I like it. Sort of works like the yield keyword in python. Nice!