Usher

Recursive program synthesis from example. Clojure implementation of paper.

What it can do

It can generate programs and even recursive programs.
It's still in alpha status. But here is what you already can do:

Run it with

lein repl
user> (use 'usher.magic)
user> (magic-length)

And the result you'll see:

if empty? i 
  then zero 
  else inc length rest i 

Which is a recursively defined length program generated with the following input:

(run
   [[ ] [2] [1 2]]     ; input examples
   [ 0   1    2  ]     ; output examples
   [{:fn zero   :ar 0} ; components
    {:fn empty? :ar 1}
    {:fn inc    :ar 1}
    {:fn first  :ar 1}
    {:fn rest   :ar 1}}])

Or we can generate Fibonacci program the same way:

user> (magic-fib)
if i <= 1
  then i
  else (+ (fib dec i) (fib dec dec i))

And that is pretty cool.
Result obtained from following examples and components:

(run
   [0 1 2 3 4 5]
   [0 1 1 2 3 5]
   [{:fn dec       :ar 1}
    {:fn #(<= % 1) :ar 1}
    {:fn +         :ar 2}])

More examples in the magic.clj file.

To do

• Optimisations (fibonacci take 5 sec to synthesize, while authors report 0.12 sec).
• Synthesize programs with arity > 1. (To generate append program.)
• More examples (append).

Research

• Will it be able to support higher-order functions?