Trump is a very simple programming language interpreter and static
type analyser that I used to illustrate my talk
Softly, Softly Typing at
Rubyconf 2015. The language consists of
numbers and functions which can both be assigned to variables, and of
a strange keywork Maybe that simulates runtime uncertainty.
The following example program demonstrates most of the capability of the Trump language:
fst = fn(x, y) { x }
snd = fn(x, y) { y }
apply = fn(x, y, z) { x(y, z) }
a = 6
b = 7
apply(fst, a, b)
When run through the interpreter, this program produces an array of output values - one element for each expression in the program. The output produced is something like:
[
#<Function...>,
#<Function...>,
#<Function...>,
6,
7,
6
]
Then running it through the type checker produces something like:
[
(a,b) -> a,
(a,b) -> b,
((b,c) -> d, b, c) -> d
<NumberType>,
<NumberType>,
<NumberType>
]