Standard ML of New Jersey (32-bit) v110.99 [built: Thu Dec 24 11:01:10 2020]
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- fun filter _ [] = []
=   | filter p (x::_) = if p x then [x] else [];
val filter = fn : ('a -> bool) -> 'a list -> 'a list
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- filter (fn x => x=0) [];
val it = [] : int list
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- filter (fn x => x=0) [1,2,30,4,5,6];
val it = [] : int list
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- filter (fn x => x=0) [0,1,2,30,4,5,6];
val it = [0] : int list
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- filter (fn x => x=0) [0,1,2,0,3,0,4,5,0,6];
val it = [0] : int list
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- fun foldl h x ys = x;
val foldl = fn : 'a -> 'b -> 'c -> 'b
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- fun foldl h x ys = h (hd ys, x);
val foldl = fn : ('a * 'b -> 'c) -> 'b -> 'a list -> 'c
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- fun foldl h x [] = x
=   | foldl h x ys = h (hd ys, x);
val foldl = fn : ('a * 'b -> 'b) -> 'b -> 'a list -> 'b
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- fun foldl _ x [] = x
=   | foldl h x (y::_) = h (y, x);
val foldl = fn : ('a * 'b -> 'b) -> 'b -> 'a list -> 'b
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- fun foldl _ x [] = x
=   | foldl h x (y::ys) = foldl h (h (y, x)) ys;
val foldl = fn : ('a * 'b -> 'b) -> 'b -> 'a list -> 'b
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- foldl;
val it = fn : ('a * 'b -> 'b) -> 'b -> 'a list -> 'b
- foldr;
val it = fn : ('a * 'b -> 'b) -> 'b -> 'a list -> 'b
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