gulcii-0.3: lib/edinburgh.gu

# boolean
false = \ t f . f
true = \ t f . t
and = \ a b . a b a
or = \ a b . a a b
not = \ a . a false true
# function
id = \ a . a
const = \ a b . a
compose = \ bc ab a . bc (ab a)
flip = \ abc b a . abc a b
fix = \ f . (\x . f (x x)) (\x . f (x x))
error = \e . error e
seq = \ a ! \b . b
# list
nil = \ c n . n
cons = \ x xs c n . c x xs
null = \ l . l (\x xs . false) true
head = \ l . l (\x xs . x) (error head)
tail = \ l . l (\x xs . xs) (error tail)
map = \ f l . l (\x xs . cons (f x) (map f xs)) nil
append = \ us vs . us (\x xs . cons x (append xs vs)) vs
filter = \ p l . l (\x xs . p x (cons x) id (filter p xs)) nil
index = \ l n . n (\p . l (\x xs . index xs p) (error index)) (l (\x xs . x) (error index))
reverse = \ l . l (\x xs . append (reverse xs) (cons x nil)) nil
foldr = \ f e l . l (\x xs . f x (foldr f e xs)) e
length = foldr (const succ) zero
ands = foldr and true
ors = foldr or false
concat = foldr append nil
all = \f . compose ands (map f)
any = \f . compose ors (map f)
concatMap = \f . compose concat (map f)
composes = foldr compose id
sum = foldr add zero
product = foldr mul (succ zero)
repeat = \x . cons x (repeat x)
cycle = compose concat repeat
take = \n l . n (\p . l (\x xs . cons x (take p xs)) nil) nil
drop = \n l . n (\p . l (\x xs . drop p xs) nil) l
transpose = \l . l (\xs xss . xs (\y ys . cons (cons y (concatMap (take 1) xss)) (transpose (cons ys (map (drop 1) xss)))) (transpose xss)) nil
iterate = \f x . cons x (iterate f (f x))
last = \l . l (\x xs . xs (\y ys . last xs) x) (error last)
replicate = \n x . take n (repeat x)
# natural
zero = \ s z . z
succ = \ n s z . s n
infinity = succ infinity
even = \n . n odd true
odd = \n . n even false
add = \ m n . m (\p . succ (add n p)) n
mul = \ m n . m (\p . add n (mul n p)) zero
exp = \ m n . n (\p . mul m (exp m p)) one
sub = \ m n . m (\p . n (sub p) m) zero
equal = \ m n . m (\mm . n (\nn . equal mm nn) false) (n (\nn . false) true)