math with gfcc

examples/tutorial/embedded/TransferDefGFCC.hs

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+module TransferDefGFCC where
+
+import GF.Canon.GFCC.GFCCAPI (Tree)
+import GSyntax
+
+transfer :: Tree -> Tree
+transfer = gf . answer . fg
+
+answer :: GQuestion -> GAnswer
+answer p = case p of
+  GOdd x   -> test odd x
+  GEven x  -> test even x
+  GPrime x -> test prime x
+
+value :: GObject -> Int
+value e = case e of
+  GNumber (GInt i) -> fromInteger i
+
+test :: (Int -> Bool) -> GObject -> GAnswer
+test f x = if f (value x) then GYes else GNo
+
+prime :: Int -> Bool
+prime x = elem x primes where
+  primes = sieve [2 .. x]
+  sieve (p:xs) = p : sieve [ n | n <- xs, n `mod` p > 0 ]
+  sieve [] = []