Some examples

ex/fft.surf

-/*-------- Fast Fourier transform --------*/
-// Language: Surface
-// Checking: ../compiler.exe Surf fft.surf
-
-let vec_vec u v = $fold (+) 0 ($map2 (*) u v)
-let mat_vec A u = $map (vec_vec u) A
-let mat_mat A B = $map (mat_vec A) ($transpose B)
-
-
-// Extract smaller divisor of n
-let div n = 1 /*
-  let rec f k =
-     if k * k < n then 1 else
-       if n % k = 0 then k else
-         f (k+1)
-  in f (2)
-**/
-// Dummy exponential and pure imaginary unity
-let exp x = 1+x*(1+x/2*(1+x/3*(1+0)))
-let i = 1
-let pi = 3
-
-
-let rec fft <<n>> (x:[n]_) : [n]_ =
-
-  // Twiddle factors
-  let tw [j,k] = exp (2*i*pi*j*k/n) in
-
-  // One step of decomposition
-  let dft <<n,p>> =
-    |> $split
-    |> $map fft <<n>>
-    |> $transpose |> $map2 ($map2 (*)) tw
-    |> $map fft <<p>>
-    |> $flatten
-  in
-
-  // Recusive call
-  let size d = div n in
-  let size k = n / d in
-  if d = 1 then mat_vec tw x else
-    (dft <<d,k>> (x:>[k*d]_) :> [n]_)
-
-
-
-
-let rec fft <<n>> : [n]_ -> [n]_ =
-
-  // Twiddle factors
-  let tw [j,k] = exp (2*i*pi*j*k/n) in
-
-  let size d = div n in
-  let size k = n / d in
-  if d = 1 then mat_vec tw else
-    :> [k*d]_
-    |> $split
-    |> $map fft <<d>>
-    |> $transpose |> $map2 ($map2 (*)) tw
-    |> $map fft <<k>>
-    |> $flatten
-    :> [n]_
-
-
-
-// Twiddle factors
-let tw n [j,k] = exp (2*i*pi*j*k/n)
-
-let rec fft <<n>> : [n]_ -> [n]_ =
-  let size d = div n in
-  let size k = n / d in
-  if d = 1 then mat_vec (tw n) else
-    :> [k*d]_
-    |> $split
-    |> $map fft <<d>>
-    |> $transpose |> $map2 ($map2 (*)) (tw n)
-    |> $map fft <<k>>
-    |> $flatten
-    :> [n]_
-
-let repeat <<n>> c [_<n] = c
-let repeat2 <<n,p>> =
-  |> repeat <<n>>
-  |> repeat <<p>>
-

ex/test-polymorphism.surf

-/*-------- Examples on type variables generalization --------*/
-// Language: Surface
-// Checking: ../compiler.exe Surf test-polymorphism.surf
-
-let ign _ _ = false
-
-// Generalization of quoted type vars (top-decl)
-let f x = let g : 'a = fun x -> x in g (x)           // SUCC
-let f = let g (x:'a) = x in ign (g 0) (g  42 )       // SUCC
-let f = let g (x:'a) = x in ign (g 0) (g true)       // FAIL
-let f = let g (x: _) = x in ign (g 0) (g true)       // SUCC
-let f x = let g (x:'a) = x in ign (g x) (g x)        // SUCC
-let f = let g (x:'a) (y:'b) = x=y in g true false    // SUCC
-let f: type a. a -> _ = fun x -> let g (x:'a) = x in ign (g x) (g true)  // FAIL
-let f:      bool -> _ = fun x -> let g (x:'a) = x in ign (g x) (g true)  // SUCC
-let f: type a. a -> _ = fun x -> let g (x: _) = x in ign (g x) (g true)  // SUCC
-
-let z = let i x =  x     in i i 0 // SUCC
-let z = let i x = (x:'a) in i i 0 // FAIL
-
-// Type var escaping
-let f (x:'c) : 'd = x          // SUCC
-let f (type c d) (x:c) : d = x // FAIL
-let f (type a) (x:a) y = x = y // SUCC
-let f x = let g: type a. a -> _ = fun y -> x = y in g (x) // FAIL
-let f: type a. a -> _ = fun x y -> x = y                  // FAIL
-